Learning Objectives

By the end of this module, students should be able to:

• analyze real-world data on the global distribution of cities identified as most vulnerable to coastal flooding;
• consider the multiple variables that determine the ranking of these cities in the present and future; and
• use geospatial skills with Google Earth to explore and compile data for a variety of coastal communities at risk from coastal flooding.

Module 1 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

Currently, more than 10% of the world’s population (currently estimated at 634 million and growing) lives on land that is within 10 meters in elevation from sea level. Some of the world’s most populated regions lie within this elevation range. Another way to view this is that 75% of the world's cities are on a coast. Coastal communities in the U.S. are home to 123 million people. In many regions of the world, migration to coastal population centers is occurring at a rapid pace. These low-lying cities include London, New York, Miami, and Tokyo, as well as Mumbai in India, and the rapidly growing megalopolis of Guangzhou in China, and other large cities we may rarely think about. Numerous smaller, little-known communities are equally precariously located but come into sudden focus when a disaster strikes. Tacloban in the Philippines, which was devastated by Super Typhoon Haiyan in 2013, is a good example. Meanwhile, low-lying U.S. cities, such as Boston, Miami, and New York, all face a future that will require adaptation to more frequent flooding from the ocean.

We know that while populations have increased in coastal cities, Earth's sea level has also been rising at an increased pace. These two factors have contributed to an increased probability of inundation of coastal communities by storm surges, high tides, and other events. The measured global sea level rise has been well documented using worldwide tide gauge and satellite altimeter data. This shows that during the 20th century, the global sea level rose at an increasing rate. Between 1880 and 2011, this rate was 0.07 inches (0.18 cm) per year. Between 1993 and 2011, the rate increased to 0.11 inches (0.28 cm) per year. This represents a 64% increase (US EPA). These seemingly small increments add up: sea level has risen by approximately 5 to 8 inches (13-20 centimeters) since 1900. The latest information shows that the rate of rise continues to accelerate: NASA Global Climate Change: Sea Level Latest Data (This is a very cool data portal, and we highly recommend you look at it!)

The most recent sea level rise projections from the Intergovernmental Panel on Climate Change indicate that sea levels could continue to rise another 39 inches (approximately 1 meter) by the end of this century. This may not seem like a huge amount, but communities that are currently at an elevation close to sea level are already seeing increased flooding, and this problem will continue to get worse over the next few decades, so it is no longer just a nuisance but a major issue to be tackled. There is a great deal of uncertainty in predictions of future sea level rise, so this also must be taken into account when considering the future of our coastal cities.

Mean Sea Level Trend (2.77 +/-0.09 mm/yr), The Battery, New York.

Credit: NOAA: Tides and Currents, SL Trends, The Battery, New York (Public Domain)

These rates are global averages and, in fact, sea level change varies greatly from place to place around the globe. Above is a data plot from the tide gauge at The Battery in southern Manhattan, NY, with mean sea level in meters plotted over time from 1850 to 2010 (and average rates in millimeters rise per year).

If subsidence (sinking of the land level) is factored in, a location’s relative sea level rise can be much higher than the global average. This is illustrated by comparing the tide gauge data for The Battery with that of Grand Isle, LA. (below), where subsidence of the Mississippi River Delta sediment exacerbates sea level rise rates considerably – a difference in sea level rise of 6.47 mm/year between these two locations! We will explore these ideas further in later modules.

Mean Sea Level Trend (9.24 +/-0.59 mm/yr), Grand Isle, Louisiana.

Credit: NOAA: Tides and Currents, SL Trends, Grand Isle, Louisiana (Public Domain)

Sea Level Rise: The Uncertainty of Predicting Future Sea Levels

The following modules will explore in detail sea level changes in relation to coastal processes and hazards, and their impacts on coastal communities. Here in Module 1, we will touch on the topic of sea level rise. Our goal is to examine coastal cities globally and consider the hazards presented by sea level rise. You will learn about some of the controversies surrounding the prediction of future sea levels. The links we have provided will help explain how the predictions are made. The sea level rise predictions used – now given to be approximately 1 meter by the year 2100 – were made using computer modeling. The models run by different groups have provided a range of predictions, underlining the complexity of predicting future sea levels. This is an issue that is the focus of intense research. Quantifying the contribution of the melting of the polar (Greenland and Antarctic) ice sheets to sea level rise has been a source of uncertainty as scientists worked to unravel the mechanisms at work. Scientists are now more confident in determining the contribution of the water flowing from the ice sheets, but it seems that the projected sea level rise rate increases as more is understood about the fate of the ice sheets. However, current research has given coastal managers an estimate of a 1-meter rise by 2100 to use in their planning for the protection of coastal communities in this century.

Storm Frequency and Intensity

Another factor that impacts the coastal hazard risks experienced by coastal communities is storm frequency and intensity. The International Panel on Climate Change reports that predictive modeling suggests that storms could become more intense in the future. However, the frequency of storms may actually decrease. This quote from IPCC Climate Change, 2007, sums up the evidence for these predictions from modeling results:

“There is evidence from modeling studies that future tropical cyclones could become more severe, with greater wind speeds and more intense precipitation. Studies suggest that such changes may already be underway; there are indications that the average number of Category 4 and 5 hurricanes per year has increased over the past 30 years. Some modeling studies have projected a decrease in the number of tropical cyclones globally due to the increased stability of the tropical troposphere in a warmer climate, characterized by fewer weak storms and greater numbers of intense storms. A number of modeling studies have also projected a general tendency for more intense but fewer storms outside the tropics, with a tendency towards more extreme wind events and higher ocean waves in several regions in association with those deepened cyclones. Models also project a poleward shift of storm tracks in both hemispheres by several degrees of latitude”.

Investigating Coastal Community Vulnerability Around the World

The following two pages include a look at coastal communities around the world and their relative vulnerability to coastal flooding, based on research. These materials are important to developing a context for the course and can also form a foundation for the Capstone Project. These pages include Learning Check Points designed to help enhance your understanding. These questions are asked for your benefit; you are encouraged to answer them, since they frequently introduce methods and applications that you will need to use again during graded assessments and in your Capstone. They are not for credit, but you need to take the time to do them, as they are often required knowledge for other assessments.

To get started on the Module 1 Learning Check Points, click the first link below or use the menu.

Introductions and Exploring US Coastal Property Risk from Rising Seas Interactive ArcGIS Story Map

Overview

This discussion will allow you to introduce yourselves to each other while diving into some core content.

In this module, we have examined the global distribution of cities identified as most vulnerable to coastal flooding and considered the multiple variables that determine a community's ranking.

For the Module 1 Lab A Graded Discussion, we will spend time looking at one more source of data that can be used to look at future scenarios for U.S. coastal communities and their risk of chronic inundation in the future. You will use this tool to explore what this may mean to a couple of coastal communities and respond to a prompt on this topic in the discussion forum. You will also respond to at least one other student's responses throughout the week.

Once you read this description, return to your course management system to participate in the discussion.

Discussion Prompt

Please write a short personal introduction and tell us about yourself, and what interests you about this course. Perhaps you have personal experiences from living or vacationing in a coastal city. In addition to your introduction, after listening to the podcast and exploring the interactive mapping tool, and your observations from these two sources, briefly describe what a homeowner is facing in the next 25 years in one of the two communities you chose to examine on the map (include the name of the city). How does this change in the 50 years following this period? What advice would you give to a 30-year-old person buying property in this location with a 30-year mortgage who is planning to raise a family in this community? Provide evidence from this module to back up your answer.

Instructions

1. Use Word or another text editor to respond to the prompt with your thoughts backed up with evidence from Module 1. The length of your response should be between 200 and 400 words. (Typing your response in Word or another text editor and then copying/pasting from Word or similar to this discussion forum is recommended to avoid losing your work midstream in the event of an accidental browser closing, intermittent Internet connectivity, etc.)
2. Go to the Module 1 Lab A (Discussion) Assignment in your course management system.
3. Type or copy/paste your response to the prompt into the text box marked 'reply' and select Post Reply by 11:59 p.m. Thursday.
4. Your response is now visible to your classmates and your instructor. Read through others’ responses and write a thoughtful reply to at least one other student by the date listed on the calendar. These replies should be either a rebuttal in which you add your ideas in the form of a persuasive argument (written with respect for the originating author), or a response that agrees with, supports, and builds upon the original response. Because a timely response to the conversation is part of your grade, subscribing to the forum is required. Check in to the discussion forum often throughout the week to post and respond to comments. Your responses to at least one other classmate should be posted by 11:59 p.m. Sunday to allow for authentic discussion to occur.

Grading

The grading rubric will help you understand what constitutes an appropriate level of participation on your part. The instructor reserves the right to not award any credit (including points for timing and interaction) if the content of the posts, however on-time they may be, is off-topic, offensive, or otherwise inappropriate. Such posts may be deleted at any time by the instructor as well.

Introduction

In this Lab, we present two coastal communities at risk from coastal hazards - Guangzhou, China, and New Orleans, USA. You will use Google Earth tours to explore these communities. For each place, you will spend time looking at ground level views to gain an overview of the place in terms of its elevations; proximity to tidal water; the type of topography in the area (are there higher elevation places nearby?); the presence of major river/ river delta; presence or absence of flood control structures. If you are not sure of something, make observations in Google Earth, read the profiles in the online materials, go to links to more profiles, and/or search for specific information about the topic on the Internet. You will compare and contrast the economic factors that drive society in the two communities. The goal is for you to become fully comfortable using Google Earth.

Downloads/Resources

Module 1 Lab B Worksheet

KMZ file (Please note, there are many cities in the file. You only need to focus on Guangzhou, China, and New Orleans, but feel free to explore the other cities!)

City Profile: Guangzhou, China*

City Profile: New Orleans, LA*

*Profiles are also available on the next two pages.

Instructions

Before you begin the Lab, you will need to download the Lab worksheet and Google Earth file. In addition, you will need to read the two City Profiles mentioned above. We advise you to either print or download/save the Lab worksheet, as it contains the steps you need to take to complete the Lab in Google Earth. In addition, it contains prompts for measurements and questions that you should take note of (by writing down or typing in) as you work through the Lab.

Once you have worked through all of the steps and completed the measurements, you will go to the Module 1 Lab B (Quiz) in your course management system to complete the Lab by answering multiple-choice questions. The answers to questions on this Lab worksheet will match the choices in the multiple-choice questions. Complete the Module 1 Lab B (Quiz) for credit.

This module has introduced some broad ideas about the distribution of communities around the world that are experiencing increased vulnerability to coastal hazards due to their proximity to tidal waters and various other geomorphic and societal factors. The module directed you to explore data compiled by the World Bank and other agencies that rank the vulnerability of coastal cities using many variables, including economic measures. You have gained experience in using Google Earth, a powerful free online tool that enables us to investigate places in terms of their physical (elevation, proximity to water, geographic location, etc.), and societal characteristics, including the economy. These tools have enabled you to make comparisons among cities across the globe and to reach your own conclusions about how these characteristics affect the vulnerability ranking. This module is designed to be a jumping-off point for the course and to lead into a more detailed look at coastal hazards and society.

Reminder - Complete all of the Module 1 tasks!

You have reached the end of Module 1! Double-check the Module 1 Roadmap (in Goals and Objectives) to make sure you have completed all of the activities listed there before you begin Module 2.

Goals

• Students will gain an understanding of how plate tectonics plays a first-order control on the characteristics of a coast and how other processes, such as glaciation, climate, sediment supply, waves, and tides, also influence the characteristics of a coast.
• Students will develop an appreciation for the geomorphological diversity of coastal zones.
• Students will gain an understanding of the differences between emergent and submergent coasts, depositional and erosional coasts, as well as how the hydrodynamic regime exerts a strong control on the geomorphology of the coast.

Learning Objectives

By the end of this module, students should be able to:

• examine and show, using Google Earth, the global diversity of coastal zones;
• identify the plate tectonic setting of a coastal zone based on geographic location relative to major tectonic boundaries;
• identify and be able to describe the second-order processes that can act on coastal zones;
• integrate knowledge of coastal geomorphology and understanding of coastal processes to identify the types of processes that create specific coastal geomorphologies; and
• evaluate the history of a coast based on the coastal geomorphology.

Module 2 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

What is a collisional margin? What is a passive margin?

We know from a wide range of different studies that the Earth is not a completely solid sphere but instead consists of a series of different layers ranging in composition, which dictate the way they react when forces are applied to them. The outermost layers are very different with regard to composition and density from the innermost layers of the Earth. A generalized segregation of the Earth recognizes these three primary units: crust, mantle, and core.

What are continental margins, and what is the morphology of continental margins?

Continental Margins

Before we get too far along in a discussion of plate tectonics and coastal zones, we need to address the characteristics and form of continental margins because this is where the coastal zones that we will be referring to are located. As indicated by the name, continental margins are the edges of the continents and transition into the deep-water environments of the ocean basins. In general, continental margins have several distinct physiographic subenvironments, including the continental shelf, continental slope, and continental rise (see cross-sectional profile).

Continental Shelf

The continental shelf of a continental margin includes the seafloor that extends from the subaerial part of the continent, or shoreline, seaward to what is known as the shelf break. Continental shelves are typically relatively gently sloping surfaces, but a change in the gradient, or slope, of the continental shelf takes place at what is referred to as the shelf break. There is a wide range of widths and gradients for continental shelves (see global map), but the global average water depth for where the shelf break is located is between 120 to 130 m. The global average width for continental shelves is approximately 75 km, and the average slope of the continental shelves is on the order of 6 to 8 degrees. One fundamental characteristic of continental shelves is that they can represent areas of extensive deposition because of their proximity to continental river systems that supply sediment to the continental margins. In fact, in some places, the continental shelf may be underlain by as much as 10 to 15 km of sediment, representing tens of millions of years of deposition above the granitic crust that forms the foundation of continental margins. On a global basis, the sediment at the surface of the continental shelves can derive from many different sources. Depending upon the location of the continental shelf and the characteristics of the adjacent continent, the sediment can be sourced from river systems, glaciers, and ice sheets, or can be calcium carbonate sediment sourced from organisms that produce shells of calcium carbonate.

Cross-sectional profile illustrating a continental margin and the physiographic provinces of the continental shelf, continental slope, and continental rise, which ultimately transitions into the nearly flat, deep-water abyssal plain of the ocean basins. These transitions are also accompanied by a change in thickness of the underlying crust and a change in composition from granitic continental crust under the continental shelves to basaltic oceanic crust toward the open ocean basins.

Credit: Wikipedia, Public Domain

Global map of the continents, showing the transition from subaerial continents to the abyssal plains of the deep ocean basins. The light blue coloration along the edges of the continents represents the relatively shallow bathymetry of the continental shelves. Notice the wide range in the width of the continental shelves and that some of the narrowest continental shelves are associated with collisional tectonic margins, whereas the wider continental shelves are associated with passive tectonic margins. For example, compare the shelf width of the collisional west coast of South America with the shelf width of the passive east coast of North America.

Credit: NOAA: ETOPO1 Global Relief Model

Continental Slope

The continental shelves of the world transition into the continental slopes at the shelf break, where a distinct change in the gradient or slope of the seafloor exists. This change in gradient is coincident with a reduction in crustal thickness and a granitic to basaltic change in the composition of the underlying crust. Continental slopes are narrower than continental shelves, with a global average of only 20 km. They extend from the shelf break at approximately 120 m to as deep as 3,000 m with approximately a 4-degree gradient, but may be as high as 20 degrees. Overall, slopes also vary according to the nearby plate tectonic boundary, where slopes are steepest in locations adjacent to geologically young plate tectonic margins with narrow continental shelves. Deposition on continental slopes is predominantly finer-grained than the sediment that is deposited on continental shelves because there is less moving water from waves and tides to carry large sediment particles. One exception, however, is that during past periods of low sea level, when rivers extended across continental shelves to meet the low sea level shoreline, relatively larger sedimentary particles were transported to continental slopes by river systems. As a result of the past low sea levels, some continental slopes contain buried deposits with large sedimentary particles such as coarse sand and gravel. One unique feature about the outer parts of the continental shelves and continental slopes is that they may be the sites of submarine canyons through which sediment and water can be carried out to deeper parts of the ocean basin. Through the years, there has been much speculation as to how these canyons form, but most scientists agree that their origin is a result of erosion by oceanic currents, gravitational forces that cause failures and incision, or are the remnants of river valleys formed during past lowered sea level.

Continental Rise

The continental rises are the most distal parts of the continental margins and represent the transition from the slope to the deeper, flat physiographic regions of the open ocean basins known as abyssal plains. Wedges of sediment that can be several kilometers thick and several hundred kilometers wide developed because of the seaward transport of sediment from the more shallow water continental shelves and slopes. Overall, the gradients of the continental rises are typically less than 1 degree.

For more information on continental margin physiography and morphology, see the following resource.

An Overview of Continental Margins

What are the characteristics of coastal zones along collision coasts and trailing margins?

The tectonic setting and tectonic history of a continental margin are probably the most important factors that control the character of a continental shelf and coast. You can think of the tectonic setting as a first-order control on the morphology of a coastal zone. There are other factors that certainly are important, such as sediment supply, but we will get to those in later sections.

A very useful and widely recognized classification scheme of a coastal zone is the tectonic coastal classification developed by two scientists. In 1971, Inman and Nordstrom published a scientific paper that linked different types of coastal zones to tectonic characteristics. They suggested that the most important factors in determining the coastal characteristics were:

1. location of the coast with respect to plate boundaries;
2. tectonic setting of the coastline on the opposite side of the continent;
3. time; and
4. exposure of the coast to open ocean conditions.

5. Collision Coasts

   Collision coasts face a plate boundary. They occur at the point of subduction zones, on the edge of a plate. These are tectonically active coasts, with frequent earthquakes and volcanic activity. Features found on and near collision coasts include mountains of more than 3,000 meters; deep trenches offshore, into which sediment falls when it reaches the coast. Here, the continental shelf is narrow, and there are few depositional features to be found. The rivers that drain to collision coasts are relatively small, and there are few of them.

   Examples of collision coasts are the west coasts of North and South America.

6. Trailing Edge Coasts

   Trailing edge coasts face a spreading center where new material is added to the oceanic plates (e.g., mid-Atlantic spreading center). Trailing edge coasts are near the middle of a tectonic plate and far from the plate boundary. The characteristics all trailing-edge coasts have in common are a lack of tectonic activity (no earthquakes or volcanism). There are three types of trailing-edge coasts:

   1. Amero-trailing edge coasts

      Amero-trailing edge coasts occur in the middle of a tectonic plate and face a spreading center. The coast on the opposite side of the continent is a collision coast. Characteristics of Amero-trailing edge coasts include NO tectonic activity, a wide continental shelf, and a wide, low coastal plain. There is abundant sediment deposition and, therefore, numerous depositional features. These features include marshes, barrier islands, spits, mangroves, and deltas. Examples of Amero-trailing edge coasts are the east coast of North America, the east coast of South America, and India.

   2. Afro-trailing edge coasts

      The distinguishing characteristics of Afro-trailing edge coasts are: they face a major spreading center, AND the opposite coast also faces a spreading center. The entire continent is located within a plate. They also have no tectonic activity. The continental shelf can vary in width from wide to narrow. The coast itself can feature cliffs, hills, and low mountains, and coastal plains. Sections of an Afro-trailing edge coast can have many depositional features, while other sections have very little sediment deposition, so they are highly variable. Examples of Afro-trailing edge coasts are the east and west coasts of Africa, the coast of Greenland, and parts of coastal Australia.

   3. Neo-trailing edge coast

      This type of coast faces relatively young plate tectonic spreading centers, which means that there has not been enough time for them to develop. There may be some volcanism, and they may be seismically active with rugged, young topography adjacent to them. The continental shelf is very narrow here. There is very little deposition taking place on these coasts, as few rivers enter the ocean. A few pocket beaches form, but no other depositional features. They are backed by cliffs, hills, and low mountains. Examples include the Gulf of California, where Baja rifted from mainland Mexico about 20 million years ago (relatively recent in geologic time).

7. Marginal Sea Coasts

   Coasts of this character occur along continental coasts facing an island arc. They are sheltered from the conditions of the open ocean by other landmasses, such as island arcs, which were created by the collision of tectonic plates. They feature wide continental shelves and are backed by hilly or low-lying regions. There is no tectonic activity on these coasts. There is a high sediment influx from rivers, resulting in depositional features such as deltas. Examples of marginal sea coasts include the coasts of mainland China on the South China Sea, the East China Sea, the Sea of Japan, and the Yellow Sea. The Caribbean islands form an island arc that protects the coasts of mainland Central and South America on the Caribbean Sea.

As mentioned at the beginning of this module, there have been a number of coastal classification schemes proposed throughout the time of coastal scientific inquiry. There is not enough room in this module to discuss all of these in detail, but here are a few more as food for thought and discussions that will come later in this course.

Based on the information discussed in the last several sections, it should now be evident to you that plate tectonics has a strong influence on the characteristics of continental margins and the associated coastal zones. There are, however, several other key secondary influences that also affect how coastal zones evolve. These include:

• sediment supply,
• glaciations (direct and indirect),
• climate,
• hydrographic regime.

Each of these will be discussed individually in the following sections to provide a comprehensive framework of the types of processes that need to be considered when attempting to evaluate coastal characteristics and evolution.

In this brief lab, you will record a Google Earth tour of two of the classifications of coastlines described in this module: choose either emergent or submergent for the first, and choose erosional or depositional for the other. So your submission will include two files (see below for more details).

Instructions

1. Read the material on emergent and submergent coastlines in the module and choose a location that exemplifies one of these types of coastlines from one or two of the following worldwide locations:
   Emergent:
   Any of the example locations labeled as emergent on the Emergent and Submergent Coasts page of the Module 2 course material, plus locations on the west coast of the U.S., focusing on the states of Oregon and Washington, and Scotland.
   Submergent:
   Any of the example locations labeled as submergent on the Emergent and Submergent Coasts page of the Module 2 course material, and other locations on the eastern coast of the U.S., focusing on the states of Maryland, Virginia, and North Carolina; the Gulf Coast of the U.S.; and Southern China.
   Erosional:
   Any of the example locations labeled as erosional on the Erosional and Depositional Coasts page of the Module 2 course material, plus other locations on the west coast of the U.S., Southwestern United Kingdom (England), and southern Australia.
   Depositional:
   Any of the example locations labeled as depositional on the Erosional and Depositional Coasts page of the Module 2 course material, plus other locations on the east coast of the U.S. and the Gulf Coast of the U.S.
   Be sure the location you choose for your tour has obvious features and landforms that are evidence of the classification you are highlighting.
2. To prepare for your tour, open Google Earth Pro. Cruise around that location at about 25- to 30-mile elevation, then zoom in close to about a mile (~5,300 feet or 1.6 km). Zoom in further to see greater detail (~500 ft. or 150 meters). Note the morphological features you see that make the coast fit into that classification. Examples: Do you see cliffs or a low-profile shore? Do you see a wide or narrow beach?
3. Next, write a brief 100-word script to describe the morphological features (landforms you see) that are evidence of your chosen coastline fitting into that category. Base your description on the information found in the class material, using terminology learned in the reading and other sources. The script can be informal; it will help you remember what to say when you begin recording. Be concise and limit your recording to 2 minutes or less.
4. Next, use ScreenPal to record your tour. The tool is free and easy to use.
5. Follow the instructions to 1. record, 2. save, and 3. email the MP4 file to yourself. Once you receive the emailed file, reopen it and play it in Google Earth Pro to make sure it works. Then, make a screen recording using Screenpal to add the audio narration to your tour.
6. Repeat steps 1-4 for the material on erosional or depositional coastlines, choosing to describe either an erosional or a depositional coastline example.
7. The finished product for this assignment will include two screen recordings (MP4 files) that you will submit to the Module 2 Lab (File Uploads). Name the files you upload with the type of coastline you are describing and the location (e.g., “submergent-Grand Isle.mp4).
8. NOTE: Submissions are made in your course management system.

Throughout this unit, you have been introduced to the global diversity of coastal landscapes. You have learned about the role of plate tectonics in coastal classification as well as other approaches to coastal zone classification such as recognizing whether a coast is emergent or submergent and depositional or erosional. Finally, you have been introduced to an array of other processes that operate in coastal zones and that exert an influence on the overall morphology of the coast, including climate, sediment supply, glaciation, and the relative role of waves and tides. This unit sets the stage for Unit III, which will provide an overview of very specific types of coastal sub-environments such as rocky coasts, sandy beaches, coral reefs, barrier island shorelines, and marshes and mangroves.

Reminder - Complete all of the Module 2 tasks!

You have reached the end of Module 2! Double-check the Module 2 Roadmap (in Goals and Objectives) to make sure you have completed all of the activities listed there before you begin Module 3.

• Students will build upon the material of Module 2 and be able to recognize that there are discrete, unique coastal systems such as rocky coasts, coral coasts, deltas, barrier islands, and marshlands within regional-scale coastal zones.
• Students will develop an understanding of what processes are operative within the range of coastal systems and how these processes shape the coastal systems.
• Students will appreciate that coastal systems evolve differently in response to fair-weather conditions or storm conditions.

Learning Objectives

By the end of this module, students should be able to:

• identify and describe the different types of coastal systems that exist;
• explain the morphological differences between these types of coastal systems.

Module 3 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

In what sort of tectonic setting would you expect rocky coasts most often? What is the role of different rock types in how erosion may take place along an uplifted, high wave energy rocky environment?

Rocky Coasts

Some estimates suggest that nearly 75% of the world’s shorelines are considered rocky coasts, meaning that the shoreline consists of erosionally resistant cohesive bedrock or sediment that has been recently cemented together to form a cohesive unit. Most often, rocky coasts are in areas of high wave energy and are erosional, with only localized areas where sediment might accumulate, such as small beaches between rocky headlands. They exist across a wide range of geologic settings, including very mountainous regions, areas that have been or are covered with glacial ice, or along volcanoes that are located in the open oceans. Although rocky coastlines may be present on passive, trailing tectonic margins, they are most frequently located along collisional tectonic margins.

Historically, the exact definition of a reef has been a bit controversial, and different definitions would be provided if you were to ask a geologist or a biologist. For the purpose of this discussion, a reef can be considered any organic framework that is wave resistant and modifies the environment around it because of organic growth. Keep in mind that this definition offers no information about the type of organism creating the reef. Corals, shellfish such as oysters, and even some types of worms can create reefs, although the scale of reefs created by oysters and certain types of worms is much different than the scale of reefs that can be created by corals. The Great Barrier Reef of northeastern Australia extends for nearly, 2300 km and is the only organic structure that is visible from space, whereas oyster reefs are typically only several 10s of meters in length. Fundamentally, reefs rise above the substrate that they are sitting upon and thus modify or alter the speed and direction of currents and waves.

How can beaches be zoned? What is the basis for this zonation: morphology or process? Why are some beaches steep and higher gradient than other beaches? What processes can drive sediment exchange between the nearshore, beaches, and dunes? How does the storm profile of a beach look compared to the fair weather profile for the same beach? If ample sediment is available, what can happen to a beach following a major loss of sediment? Can it recover? How?

For many of you, the concept of the nearshore, beach, and dunes probably conjures ideas such as swimming about in breaking waves, games of Frisbee on a sandy surface, or heavily vegetated mounds of sediment that have to be crossed in order to reach the beach. From a coastal geologist's morphological perspective, each of these has a unique definition, where the:

1. nearshore is a broad classification defined as the region extending from the land water interface (shoreline) to a location just beyond where the waves are breaking,
2. beach is defined as the zone of unconsolidated material that extends landward from the low water line to a place where there is a marked change in physiographic form or a line of permanent vegetation representing dunes,
3. dunes are defined as topographically elevated ridges and or mounds that may be heavily vegetated, but are formed as sand is transported by wind and subsequently deposited.

Each of these environments is unique in form and composition and is characteristically molded by fundamentally different processes that act to modify each environment on a daily or longer timescale

Zonation by Tidal Elevations

Another convenient and slightly more simplistic way of dividing the nearshore through dune system is to recognize areas along such a transect as a function of where they lie relative to the tidal range for the area. In this sense, the nearshore through the dune system can be divided, on the basis of elevation relative to mean sea level, into subtidal, intertidal, and supratidal zones.

1. Supratidal zone: is situated above the high tide elevation and only occasionally is flooded, most commonly during high spring tides and storms. It includes the uppermost part of the beach as well as the dunes, and so, the non-storm process acting to transport sediment in this area is wind (aeolian transport). In this context, this area is recognized as the backshore and dunes zone.
2. Intertidal zone: is located between the normal low and high tide levels. This zone is therefore repeatedly inundated by water and exposed to air. This also represents the zone where waves are routinely interacting with the land, leading to daily transport of sediment. In the image above this area is recognized as the foreshore or beachface.
3. Subtidal zone: consists of regularly submerged, relatively shallow water area seaward of the intertidal zone. Waves and tides are always acting to move sediment in this environment. In the image above, this area is recognized as the shoreface.

Barrier islands are shore-parallel, elongated accumulations of sand that are constructed by waves and built vertically by the accumulation of sand from wind transport. They can be found along approximately 15% of the world’s existing coastlines, with the majority of them located along trailing edge or marginal sea coasts with wide, low gradient continental shelves. In some locations, they are isolated and separated from the mainland by either open bodies of water or marsh and tidal creek systems, depending upon the hydrodynamic regime of the area. However, in some locations, they can be attached to the mainland at one end (barrier spit) or both ends (welded barrier). The length of barrier islands can range from just a few kilometers to as much as 100 km, and they can be as wide as several kilometers wide.

Satellite image of the Outer Banks, an approximately 300 km long string of barrier islands off the coast of North Carolina, U.S. The barrier islands are separated from the mainland by a series of relatively shallow water sounds. Notice how the ends of the entire barrier chain come closer to the mainland, thus reducing the size of the backbarrier open water area.

Credit: NASA (Public Domain)

Aerial view of Long Beach barrier island, New York, U.S. Notice the separation of the barrier island from the mainland by a backbarrier marsh and bay environment. Also, notice the inlet to the backbarrier along the left side of the image.

Credit: Atlantic Beach and Long Beach Aerial View by Jorfer via Wikimedia Commons (Public Domain)

Primary Morphological Components

The primary components of a barrier island system include the following:

1. Nearshore, beach, and dune systems: these environments share the same characteristics as those that were discussed in the section on beaches.
2. Backbarrier: the area located between the barrier and mainland and can consist of bodies of water such as bays, lagoons, and sounds, as well as marshes, tidal creeks, and tidal flats.
3. Bays and Lagoons: shallow, open to partially restricted water areas located in the backbarrier.
4. Marshes: salt-tolerant vegetated areas within the intertidal area of the backbarrier.
5. Tidal Flats- flat, sandy to muddy areas that are exposed at mid to low tide along the backbarrier.
6. Tidal creek: a backbarrier creek through which water flows during flood and ebb tide.
7. Tidal Inlets: openings along a shore-parallel chain of barrier islands through which water is exchanged between the open ocean and the backbarrier environments during a tidal cycle.
8. Tidal Deltas: sandy to silt-rich shoals that rise above the adjacent seafloor and are located on the landward and seaward side of tidal inlets.

Oblique aerial image of a barrier island with labeled components. Note the clearly defined ebb-tidal delta where the waves are breaking in the foreground, as well as the deeper tidal channel that connects the backbarrier to the open ocean and delivers sediment in this setting to the ebb-tidal delta. Also, notice how the inlet is constricted where sediment is accumulating at the end of the barrier island on the right-hand side, the result of longshore transport into that area, and nearshore sandbars migrating onto the beach face.

Credit: D. FitzGerald © Penn State is licensed under CC BY-NC-SA 4.0

View of a tidal inlet system along the southern North Carolina coast. Note the well-developed ebb-tidal delta and the numerous submerged sand deposits on the ebb delta, which will eventually attach to the adjacent beaches in this sediment-rich regime. Notice that the right-hand side of the tidal inlet (looking toward the mainland) contains a platform of sand that is locally infilling the inlet. The infilling of sediment on this side of the inlet, along with the curved, linear fabric of the barrier island just to the right of the inlet, suggests that the dominant longshore transport of sediment into the inlet is from the right. This type of morphology suggests that the barrier is advancing into the inlet area through the accumulation of longshore transported sediment.

Credit: D. FitzGerald © Penn State is licensed under CC BY-NC-SA 4.0

Geologic and archeological evidence clearly indicates that a significant part of the rise of modern societies and culture can be attributed to the development of the modern world's deltas, which started forming during the slowed post-ice age sea level rise. Numerous lines of evidence indicate that well-developed societies were occupying deltas in the time frame of 4,000 to 7,000 years before present because of the many natural resources that deltaic environments generally contain. Resources such as shellfish, fish, furs, and plants were necessarily taken from the wild by our ancestors, and so many ancient societies began proximal to deltaic environments.

The term delta comes from Herodotus, a Greek historian, and philosopher who recognized the similarity of the upside-down Greek letter delta (Δ) and the shape of the Nile river delta when viewed from the south toward the north.

Definition and Morphology of Estuaries

Coastal geologists define an estuary as a semi-enclosed body of water with an open connection to the ocean and one or more rivers flowing into it. They represent a transitional environment between the solid mainland and the sea and because of the inflow of rivers are partially diluted with fresh water so that they do not contain normal salinity marine water. As a transitional environment, they are influenced by marine processes, such as waves and tides, as well as river processes, such as the delivery of sediment and fresh water.

The Importance of Estuaries

Some of the world's most productive ecosystems are located within estuaries and host a wide range of organisms. In fact, many species of commercially important fish and shellfish spend part of their life cycle within estuaries before reaching maturity. They are, however, an environment that, like many other coastal environments, faces a wide range of environmental problems arising from land-use practices, dumping of sewage and other pollutants, and the introduction of excess nutrients because of poor agricultural practices.

Historically, estuaries have been classified a number of ways, including how they formed and their morphology, the circulation patterns that are present within the estuary, and the relative importance of waves and tides within an estuary. In this module, we will only be discussing estuary formation and circulation patterns of classification.

Coastal wetlands and maritime forests are unique communities of vegetation that can exist along coastal zones. They are directly affected by coastal conditions including changes in water level due to tides, coastal river influx, freshwater, saltwater, wave activity, wind and salt spray, and storm surges. Inasmuch as they are communities uniquely synced to the conditions of their environment, even subtle changes in one condition can cause widespread deleterious changes to the plants themselves.

Introduction

In this lab, you will examine a sandy shoreline's dynamics. Two types of data will be explored: shoreline erosion using Google Earth timeline and shoreline elevation change data produced from elevation profiles. These two types of data yield a great deal of information about the dynamics of a sandy, wave-dominated shoreline and reveal trends in the erosion and deposition of sediment.

Throughout this module, you were introduced to a wide range of coastal environments that exist across Earth. Each of these has a unique geomorphology that results from the interplay and influence of processes such as waves and tides, sediment supply, climate, type of bedrock, and, of course, plate tectonics.

A focus of the module was to point out that processes such as plate tectonics (Module 2) may affect the characteristics of a coast at the scale of several 100s to 1000s of kilometers along a continental margin but along such an extent of coast there may be smaller scale (10s to 100s of kilometers) coastal systems that are considerably different from one another. For example, the trailing-edge coast of eastern North America varies substantially from Canada to Florida, with rocky coastline characteristics in northeastern Canada and the northeastern U.S. to major sand-rich barrier island systems farther south around the mid-Atlantic states (e.g., Cape Hatteras of North Carolina) of the United States. These variations along a continental margin are a result of variability in sediment supply, climate, and hydrodynamic regime along the length of the eastern North America continental margin. The same type of along-margin variability in processes holds true along other continental margins, and it is clear that a unique suite of processes collectively contributes to create the wide range of global coastal geomorphologies that are evident on Earth today.

You have reached the end of Module 3! Double-check the Module 3 Roadmap (in Goals and Objectives) to make sure you have completed all of the activities listed there before you begin Module 4.

• Students will develop fundamental geospatial skills and concepts needed to assess coastal processes that produce sea level change.
• Students will be able to explain what sea level is and differentiate the mechanisms that interact to produce changes in sea level over short-term and long-term time periods.
• Students will characterize trends in sea level over geologic time and conceptualize how changes in sea level can result in various spatial scales of coastline change.
• Students will use real tidal gauge data from diverse regions to identify recent trends in sea level change, and will use these trends and NOAA Sea Level Rise Viewer data to formulate projections for future sea level positions.

Learning Objectives

By the end of this module, students should be able to:

• describe the changes in sea level change in the Earth’s geological history, to gain a perspective of modern sea level rise;
• distinguish among methods used to determine sea level changes taking place in the past, present, and future;
• identify factors (intrinsic, extrinsic, and anthropogenic) that contribute to sea level change;
• discriminate among causes of local, regional, and global sea level change and associated impacts on coastal morphology and human communities;
• locate and use key datasets and data visualizing tools to analyze sea level dynamics at different temporal scales, and their impact on coastal landforms.

Module 4 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

The following pages look at what sea level change is, and what mechanisms drive sea level change on a planetary scale.

Before we investigate these mechanisms further, let’s ask a couple of fundamental questions: What is sea level anyway? How is it measured...and why has it fluctuated during the course of geologic time? And why is it not even across the globe? As you watch the following quick video, make a list of forces mentioned that influence sea level. The video clip (3:25) was published on Nov. 25, 2013, by MinutePhysics.

Video: What is Sea Level? (3:25)

The Minute Physics video introduces a few key concepts that make measuring sea level pretty complex:

1. The Earth is not perfectly spherical, but an ellipsoid, due to its spin. This means that the Earth is “fatter” at the equator and slightly flattened at the poles, so that: “if you thought Earth was a sphere and defined sea level by standing on the sea ice at the North Pole, then the surface of the ocean at the equator would be 21km above sea level”.
2. Differential density of the interior of the Earth so that “gravity is slightly stronger or weaker at different points around the globe, and the oceans tend to "puddle" nearer to the dense spots”.
3. The mass of the continental plates creates a greater gravitational pull on ocean water than the ocean basin so that “mass gravitationally attracts oceans, while valleys in the ocean floor have less mass and the oceans flow away, shallower”.

These phenomena mean that there are peaks and valleys in the surface of the ocean – the ocean level is not uniform across the planet. These are important concepts to keep in mind as you read on.

We will also meet several other phenomena that drive sea level changes around the planet later in the module.

If you are interested in understanding climate change, and you pay attention to in-depth news stories on the topic, you have no doubt frequently heard or read references to sea level and temperature anomalies. Anomaly data are being shared with greater regularity in the media these days, so it is important to understand what we mean by terms like sea surface temperature anomalies and sea surface height anomalies. An anomaly is an inconsistency or deviation from the norm, so images are created to show where change is taking place in the ocean in either a positive or negative trend when comparing to previous data. This is sometimes referred to as Sea Surface Height Deviation data or SSHD. Sea surface height anomalies are calculated using data from satellite altimeters. Many years’ worth of thousands of measurements provide a historical mean sea surface height, and the difference between the historical mean and the sea surface measurement for a particular date is called the sea surface height deviation. This can be calculated for points over the ocean surface, providing the data for the incredible maps we are seeing that show color-coded variations in sea surface across the globe and the changes in these measurements over time and space.

In the figure below, the data show the sea surface height differences compared to the 1961 – 1990 average over the entire planet. By comparing sea surface height measurements for a particular time period with the average measured over a previous time period, the changes can be shown spatially. In the figure below, the warm colors are sea surface heights that are significantly greater than past measurements, while the cool colors are those areas showing significantly lower elevation in the sea surface. This is how sea level rise trends can be identified in different parts of the globe using satellite data.

Sea Level Anomalies: Comparing data. OSTM/Jason 2 map of sea-level anomalies from July 4 to July 14, 2008 (left) compared to the same 10-day period of data from Jason 1 (right).

Credit: Sea Level Anomalies, NASA (Public Domain)

Revisit the NASA animation "22 Years of Sea Level Rise Measured from Space" from the Module 4 Overview that shows a 22-year period of sea level change using anomaly data. It is an excellent quick visualization of these phenomena.

Thinking in the Long Term: Sea Level Change in Geologic Time

The instrumental data we explored above gives a small window of time in Earth’s recent history. To put the recent changes into context, we need to also consider long term changes in sea level.

Humans typically have difficulty thinking about time beyond a human lifespan. Geologists may be the exception to this rule, but you may belong in the category of those who find it difficult to visualize the long distant past and the long distant future and to think in terms of millions or billions of years (or even thousands of years). But understanding the changes to atmospheric and ocean changes in the geologic history of the Earth is important if we are to understand what is going on with our climate and sea levels today.

Thinking REALLY long term: Below is a graph plotting sea level over the past 540 million years - since the Cambrian era. For reference, zero on the Y-axis is where the current sea level is. We don’t need to go into a lot of detail, but you can easily appreciate that sea levels have been much higher than today for much of this period of the Earth's history. Scientists have correlated these fluctuations with changes in atmospheric carbon dioxide and ocean and atmospheric temperatures, using methods described in the next few pages.

We also must acknowledge here that some people may argue that sea levels have always fluctuated, so why is sea level rise today a big deal? Hopefully, we can shed some light on this question by looking at the changes in sea level through the history of the Earth, while considering the causes for these changes. But, perhaps the simple fact that seas are rising faster than ever before in human history is enough to facilitate action and adaptation. You also may ask, “What can we do about it?” This question will be addressed in later modules.

For a rapid and fun overview of the history of the Earth’s climate changes, watch the following fascinating monolog video. It summarizes most of the concepts to be discussed in more detail in the materials that follow.

Video: A History of Earth's Climate (11:19)

There are several takeaways from studying the two graphs on the previous page. Look closely at the data presented and answer the questions below.

Learning Check Point

What were the causes of the changes in sea levels on the Earth over time? There are multiple causes that can be divided into two groups: intrinsic, or internal drivers, originating within the Earth’s system, and extrinsic drivers, which originate outside the Earth’s system. Some of these operate over the timeframe of the Earth’s history, and others operate over shorter timeframes. Some influences are global in scale, while others are more regional or localized. The following pages are part of a partial list of these influences. These drivers are also interconnected, with one influencing another in many cases.

In order for us to connect sea level with our discussion on intrinsic and extrinsic controls and feedback mechanisms, etc., let's see another dataset that links climate history and sea level. The image below shows warm and cool periods for the last 900,000 years and has an expanded inset for the last 140,000 years.

In the inset, you will notice the long-term decline in sea levels from the last interglacial warm period, which occurred about 130 ky before the present. It is labeled stage 5e on the graphic. Sea levels declined to the lowest levels during stage 2 that occurred between 13,000 and 20,000 years ago. During this time, despite some minor short-term rise/fall events, sea levels fell from near modern sea levels to some 120 meters below present. The long-term rate of sea level fall calculation shows that sea levels fell 120 meters in approximately 100,000 years, or 0.12 m / 100 years. That is, sea levels fell by some 12 cm per 100 years, or through a simple unit conversion, the rate can be stated as 1.2 mm/year.

In the same graph, sea level rise appears to have been occurring at least for the last 18,000 years. Modern sea levels (relatively similar to highs 120,000 years ago) were achieved quite rapidly, relative to the rate of fall. Based on these numbers, 120 meters of sea level rise appears to have occurred in 18,000 years. This represents a rate of almost 6 mm/year for a rise rate.

This asymmetrical pattern of sea level rise/fall rates is repeated again and again for many of the earlier glacial-interglacial episodes. Thus, there is evidence that shows sea level fall (and building of ice sheets) is a long, drawn-out process where cooling and various positive feedback loops help to reinforce the cooling. The end result is an extended period of sea level fall (i.e., iteratively more albedo, and less and less insolation delivery, more cooling, etc.).

Conversely, once the factors that initiate warming begin to turn on, warming and associated sea level rise apparently can proceed at a much faster rate until a maximum sea level is reached, and factors that influence cooling initiate and bring sea levels down again.

Prior to the last few centuries, the system was controlled primarily by extrinsic and intrinsic variables. However, human impacts on landscapes, oceans, and climate (i.e., deforestation, greenhouse gas concentrations, nutrient runoff, aerosol pollution, and cloud development, etc.) have added variables that weren't present at any previous time (more on this later).

Now, let's look at a couple of more composite analyses that help us understand signals and signatures from the last few 1000 years. In the graphic below, a number of different datasets from Australia, South America, the Caribbean, the western Pacific, and other areas have been plotted to show sea level positions. Most of these datasets are derived from investigations of coral reefs that have drowned as sea level has risen.

From what is observed in the figure above, sea level rise rates appear to have been relatively low during the initiation of rise (i.e., from 20,000 to approximately 15,000 years ago), at which point a significant increase in sea level rise rates (Meltwater Pulse 1A), and several others ensued. Three rapid increases in rise rates ("pulses") are noted here so that the majority of the 100 meters of sea level rise occurred from 14,000 to approximately 8,000 years ago, or 90 meters in roughly 6,000 years. This yields a sea level rise rate of 0.015 meters per year or 1.5 centimeters per year or 15 mm per year.

This is an incredibly fast rate that is tied to the decay of large ice sheets, including both the Eurasian and Laurentide Ice Sheets. The Laurentide Ice Sheet on North America had mostly retreated from North America by 6,000 years ago, leaving behind only the alpine ice sheets. Check out the video below showing the retreat.

Video: Laurentide Ice Sheet (00:32) No audio.

As these large ice sheets and their albedo potential were removed, the rate of absorbance of incoming solar radiation was likely to have contributed to further warming and increased temperatures of seawater. Thus, geoscientists are increasingly confident in the two primary factors that have contributed to the sea level rise rate prior to human influences. The primary cause is thought to be tied to thermal expansion of seawater, as we discussed previously. The second is the role of melting glaciers and increased volumes of land-ice being moved to the oceans.

In the human timeline, the change from higher rates of sea level to lower rates of sea level rise coincided with the onset of the Neolithic interval ~4,000 years ago. Although human beings began to influence Earth in interesting ways within the last few millennia, (think Roman Empire, which began to expand about 2,000 years ago), anthropogenic impacts on sea levels likely occurred more recently. Feedback loops often have significant lag times.

As human populations grew and the demand for freshwater for agriculture and other industries increased, and as forests were deforested, significant volumes of water re-entered the ocean-climate system and contribute to sea level rise. Some calculations suggest that perhaps as much as 5 percent of the sea level rise observed in the last few decades may be from these sources.

In 2016, the Earth’s atmospheric carbon dioxide concentration reached the 400 parts per million threshold level. This was highly significant to climate scientists and all people concerned about the effects of climate change on the planet. The amount of CO2 in the atmosphere has increased from about 280 ppm since 1750 AD at the beginning of the Industrial Revolution to its current level of 420 ppm. This is significant because of the observed effect that these increased levels of, a powerful greenhouse gas, have on the warming of the atmosphere and in turn the ocean.

Climate scientists agree that this steady increase in carbon dioxide levels (as well as other greenhouse gases – water, methane, nitrous oxide) is the cause of the warming of the planet. The burning of fossil fuels by humans over the past few centuries has “unleashed vast reservoirs of fossil carbon stored in the Earth for hundreds of millions of years.” (Hearty). When the concentration of these compounds increases in the atmosphere, so to do global temperatures, as greenhouse gases limit the escape of long-wave radiation (thermal energy). These interactions result in a warmer climate, which means more glacial ice is being melted. When combined with more water released into the ocean, warmer ocean waters also expand in volume and result in higher sea levels.

If we look at the Earth’s history, it is extremely rare for Earth to have 400 ppm of carbon dioxide in its atmosphere. Paleoclimate research using ice core data shows that about 3 million years ago the atmosphere contained 400 ppm carbon dioxide. Then the sea levels were 10 – 40 m higher than today. In more recent Earth history, 800,000 years ago, during an interglacial period, there was 300 ppm CO2. As we discussed above, ice core data show that fluctuations in the Earth’s sea levels parallel atmospheric CO2 levels.

All this is evidence for the argument that as we continue to pour more CO2 into the atmosphere with continued fossil fuel energy reliance, we can expect sea temperatures and sea levels to continue to rise in tandem with the CO2 concentration. There are many other implications that go along with this scenario. We must remember the positive feedback mechanisms, such as that in which the melting of Arctic ice reduces the albedo effect – or the reflective nature of the white snow and ice. These types of mechanisms have the effect of accelerating warming and therefore increasing the melting of ice and, in turn, increasing sea levels.

Let’s look at the data from tide gauge records, graphed over the entire 20th century and into the 21st Century. The graph below represents a composite of 23 tide gauge records from around the globe for the last century (1880 to 2000), and altimetry data superimposed since 2000 (red line).

Recent sea level curve for the last 120 years or so (1880 to 2000) based on instrumental records (not proxy records) taken by both tide gauges and by satellites. Each tide gauge station is represented by a different color and the average of all sites is shown by the bold black line. Altimetry data, a relatively recent contribution, is shown in red for the last couple of decades.

Credit: Recent Sea Level Rise by Robert A. Rohde, Gloabal Warming Art, CC BY-SA 3.0, via Wikimedia Commons

Each individual record shows the volatility (ups/downs) in water levels attributed to seasonal sea level changes that we have also previously discussed. To reduce this volatility, scientists employ a statistical averaging technique that calculates the average sea level of each successive three-year interval for all sites and then plots the average point on the graph. In this case, the moving average line is represented by the thick black line. Although it is still "wiggly," it is much smoother than the highly wiggly lines from which it is derived. This technique helps to "see the forest through the trees," so to speak.

Although a clear trend is visible in the 12 decades of data, the smoothed record helps to identify longer-term trends that are obscured by the highly variable local datasets. In this case, you will notice that there are essentially two modes in the longer-term trend. The first mode lasts roughly from 1880 through 1920, with a fairly stable sea level. In fact, the average sea level for this interval is used as the datum for this graph.

By 1920, the rate of sea level rise accelerates, and water levels begin to rise at a relatively constant rate through 2000 when satellite altimetry methods and data (red line) become available and help to substantiate tidal gauge methods.

These data show that sea level has risen an average of 20 cm (200 mm) over the last 80 years. This equates to a sea level rise rate of about 2.5 mm/year for the 80-year interval. If we take another look, including data collected since 2000, NOAA scientists show that the rate is accelerating again and a rate of 3.2 mm/yr. Has been established as the most current estimate.

The International Panel on Climate Change (IPCC) has set an estimated projected sea level rise at between 0.5 and 1.5 m by 2100. Many scientists argue that this is a too conservative estimate.

These estimates are based largely on the thermal expansion of seawater as the ocean surface heats up. However, the possibility of a significant contribution from the melting of ice sheets in Greenland and East and West Antarctic is not currently an important factor in IPCC predictions. Stay current as this research develops and estimates are adjusted accordingly.

One of the biggest uncertainties that has caused scientists to tend towards conservative estimates of sea level changes in recent years (and result in the frequent announcements of increased projections in the past few years) is the rate at which the Earth’s polar ice sheets are melting. In the 2007 IPCC report, the sea level rise projection agreed upon was a conservative 60 cm (~ 2 ft.). This number did not account for the possibility of rapid ice flow from Greenland or the Antarctic into the sea. These two ice sheets alone hold enough water to raise sea levels by 65 meters compared to 0.4 meters from all the world’s mountain glaciers. But, at that time, researchers felt that there was insufficient understanding of the ice sheets to be certain, so the IPCC resisted putting a number on it.

The most recent IPCC report (2013) increased this estimate to 98 cm or almost 1 meter.

This number has been bumped up further since 2014 with the most recent projections ranging from 0.2 to 2.0 meters (See NOAA Sea Level Rise viewer information in Module 4 Lab for more on these ranges).

Eliminating the uncertainty around quantifying the contribution of ice sheet melt-water to sea level increases is attributed to observations from NASA/German Aerospace Center’s twin Gravity Recovery and Climate Experiment (GRACE) satellites. These data indicate that between 2002 and 2016, Antarctica shed approximately 125 gigatons of ice per year, causing global sea level to rise by 0.35 millimeters per year.

In 2002, NASA launched the GRACE satellites, which track both ocean and ice mass by measuring changes in the Earth's gravitational field. The paired satellites orbit the Earth together and are spaced roughly 200 kilometers apart. Ice and water moving around the Earth exert different gravitational forces on the GRACE satellites. The satellites can sense the minuscule changes in the distance between one another caused by the change in gravitation force, which they measure and used to track water and ice mass change. It's thanks to GRACE that we know where the water flowing into the ocean came from. According to GRACE, melting of ice in Greenland increased sea level by 0.74 mm/year and melting in Antarctica by 0.25 mm/year since 2002. (Source: Smithsonian)

How do the IPCC and other agencies arrive at these numbers: Current rate of sea level rise: 3.2 mm/ year (Source: NASA: Global Climate Change); Sea Level rise predictions: 0.2 – 2.0 meters rise by 2100 (NOAA)? The numbers, which are frequently adjusted and may vary according to the source, are achieved using modeling methods of different kinds.

Earth System Models integrate the interactions of atmosphere, ocean, land, ice, and biosphere to estimate the state of regional and global climate under a wide variety of conditions. They numerically model the atmosphere, oceans, land, and sea ice, and have biogeochemical components (for example, dynamic global vegetation models) to study the carbon cycle.

Earth System Models of Intermediate Complexity (EMICs)

Models of intermediate complexity bridge the gap between conceptual models with many simplifying assumptions, and extremely complex, three-dimensional models that attempt to include as many known processes as possible. (Source: NASA: Sea Level Change)

The data gathering by the many satellite missions described above is producing datasets that are used to populate the models. Modeling ocean and sea surface height is responsible for the creation of the incredible simulations seen in this module.

Although models can help tremendously in understanding complex interactions among components of Earth systems and their outcomes, they are never perfect, and all are given ranges of confidence due to uncertainty. They must be compared to observations to iron out their inherent errors. The challenges involved in modeling the contributions of the ice sheets to sea level rise have reduced the ability to provide a full picture of what is happening in the oceans. This area is a growing field, and we are likely to hear about breakthroughs in modeling these aspects of climate change in the near future. The figure below shows sea level curves based on the IPCC AR4 report, which estimates a sea level rise of 0.8 meters by 2100.

Projected sea level rise for the 21st century. Purple bar represents uncertainty from thermal expansion of seawater; red bar represents uncertainly from ice sheet melting.

Credit: This image is from Australia's Marine and Atmospheric Research, Commonwealth Scientific and Industrial Research Organisation (CMAR/CSIRO) Climate Science Center website. View more excellent images showing sea level change data.

The figure above illustrates the levels of uncertainty that exist in the current data when using models to project future sea level rise. The AR4 IPCC data here show projected sea level curves through the year 2100. At 2095 the magenta bar shows a range of model projections (90% confidence limits), and the red bar shows the upper range extended to allow for the potential but poorly quantified additional contribution from a dynamic response of the Greenland and Antarctic ice sheets. Because there is a great deal of uncertainty surrounding the rates at which these ice sheets will melt in the future, a wide range of potential sea level rise scenarios are plotted. As the understanding of the mechanisms at work causing the melting of the ice sheets, the uncertainties shown here will most likely become more resolved in the future.

The overall takeaways from the detailed discussions of sea level in this module are:

• sea levels are not uniform across the planet, so when we talk about mean sea level rise, these averaged numbers used tend to gloss over the fact that some places are experiencing greater or lesser effects, depending on many variables;
• the drivers of sea level changes over the history of the Earth are complex (including intrinsic and extrinsic factors) and feedback loops work to create cycles of sea level rise and fall, while maintaining an overall equilibrium;
• mean global (eustatic) sea level has been rising steadily during the 20th and early 21st Centuries;
• relative sea level rise causes large local differences in rates of sea level rise. Subsidence of the land can exaggerate sea level rise, while geologic uplift can cancel out some of the effects;
• the current rate of global sea level rise is quantified at 3.2 mm/ yr., a number which has increased in recent years, based on strong evidence that the rate of sea level rise is increasing;
• the chief driver for the acceleration in sea level rise in the past one hundred to two hundred years appears to be anthropomorphic in origin and caused by rapidly increasing atmospheric carbon dioxide levels due to fossil fuel combustion;
• paleoclimate research has established that sea levels have been much higher than today for much of the Earth’s history, with many factors at play, but atmospheric carbon dioxide levels appearing to be a chief driver in climate changes;
• glacial and interglacial periods during the past 500,000 years have been responsible for periods of rapid sea level rise, followed by periods of slower sea level fall as climate cools, glaciers form, and water is once again locked up in ice;
• the exact rates of increasing sea level depend on factors, such as rates of ice melt from polar ice caps, that are currently not understood well enough to give accurate projections;
• the Earth system science models are being refined continually, using more exact data from satellites, and will improve the ability of scientists to predict future sea levels;
• current projections for the end of the 21st Century are between 1 and 2 meters of sea level rise;
• a worst-case scenario suggests that if all the ice in Antarctica and the Arctic were to melt, there would result in a rise in sea level of 65 meters!

The implications of sea level rise – even the conservative projections – are huge for the millions of people around the world living in coastal communities. In Modules 5 and 6, we will consider how coastal catastrophes impact societies and how these societies are responding.

Reminder - Complete all of the Module 4 tasks!

You have reached the end of Module 4! Double-check the Module 4 Roadmap to make sure you have completed all of the activities listed there before you begin Module 5.

Introduction

In this Lab, you will:

• Use the PSMSL website and Google Earth to explore historical records from tide gauges around the U.S. that provide reliable long-term data sets, to gain an understanding of different rates of sea level change on the Pacific, Atlantic, and Gulf coasts.
• Use NOAA's Sea Level Rise Viewer to make observations and compare sea level change predictions in locations around the U.S.

Lab Overview

There are two parts to this Lab.

• Part I is Analyzing Sea Level Change Using Tide Gauge Data. Download the tide gauge Google Earth KMZ data file from the PSMSL site. Use the tide gauge data to answer questions 1-14.
• Part II is the NOAA Sea Level Rise Viewer. After exploring and figuring out how to manipulate the viewer to give you the information for projected sea levels at the location of interest for different years, use the viewer to answer questions 9-15.

Part I: Analyzing Sea Level Change Using Tide Gauge Data

In Part I of this Lab, you will use data obtained from the Permanent Service for Mean Sea Level (PSMSL) in conjunction with Google Earth. A KML file is provided by PSMSL to open in Google Earth, making data access seamless. The sea level data are monthly and annual means referenced to a common benchmark and are referred to as a Revised Local Reference (RLR). This data is used to create accurate time series to observe trends. We are choosing four tide gauges with long time series. The longer the time series (more data), the more reliable the data are for looking at trends. You will notice short-term variability in the data – more in some locations than others. As you work through the lab, consider the difference between short-term and long-term time-series data and the reasons for the short-term variability that makes the data “noisy."

PART II: NOAA Sea Level Rise Viewer

Sea-level rise is expected to accelerate in the immediate future. However, even using the annual rates you calculated from the tide gauge data from the 20^th Century and early 21^st Century, a steady rise would be expected.

In Part II of this Lab, you will use the NOAA Sea Level Rise Viewer to help you visualize what these levels would look like in particular locations around the U.S.

You will keep your calculated rates in mind for each place from Part I, as you work with the viewer and consider the factors that influence the future projections of increased sea level rise.

NOAA built the viewer based on data that calculates a projected Global Mean Sea Level (GMSL) for 2100 to be between 0.3 m and 2.5 m. The model uses five GMSL rise scenarios: Intermediate-Low, Intermediate, Intermediate-High, High, and Extreme, which correspond to GMSL rise by 2100 of 0.5 m, 1.0 m, 1.5 m, 2.0 m, and 2.5 m, respectively (NOAA). For more detail on the science behind the Sea Level Rise Viewer, please take the time to read at least the Executive Summary and Introduction of NOAA Technical Report NOS CO-OPS 083 “Global and Regional Sea Level Rise Scenarios for the United States” listed in Resources.

Downloads/Resources

• Module 4 Lab Worksheet
• Tide Gauge KML File (see downloading directions below)
• Global and Regional Sea Level Rise Scenarios for the United States (Executive Summary and Introduction)
• NOAA Sea Level Rise Viewer Note: The viewer functions better if you use Google Chrome.

• Students will continue to develop the fundamental geospatial skills and concepts needed to assess cyclones and their formation.
• Students will develop an understanding of the relationships between the atmosphere and hydrosphere that result in the development of cyclones.

Learning Objectives

By the end of this module, students should be able to:

• describe the atmospheric conditions that are required for the formation of tropical and extra-tropical cyclones;
• analyze case studies of how coastal systems are impacted by cyclones;
• investigate geomorphological changes that result from coastal hazards.

Module 5 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

Tropical cyclones are storms that are born in tropical oceans and depend on warm water for their source of energy. They originate between 4° and 22° S of the equator, and between 4° and 35° N of the equator. During the northern hemisphere’s summer (July-September), most of the energy is delivered to the sub-tropical region of the northern hemisphere. The result is the development of large cyclonic (counterclockwise rotating) cells that are termed hurricanes if they form near North America and typhoons if they are formed in the western Pacific. Tropical cyclones do not, however, occur in the equatorial zone. More than two-thirds of tropical cyclones occur in the northern hemisphere and occur between May and November, when the ocean is at its warmest, with a peak in August and September. In the southern hemisphere, they occur between December and April, with peaks in January and February, where they are typically called cyclones.

How Do Hurricanes Form?

We generally associate tropical cyclones with the damage they do when they come in contact with land, but they spend most of their “life” out in the ocean and are a phenomenon best explained in terms of heat transfer between the atmosphere and the ocean.

The Birth of a Cyclone

The generation of a tropical cyclone is dependent upon the transfer of thermal energy from the ocean to the atmosphere. When significant volumes of warm water vapor move upwards, low-pressure cells develop at the Earth's surface and large storms are generated. In the process, water vapor evaporated into the atmosphere will cool and condense. This is ultimately how storm clouds are produced. As the water begins to fall back to the surface, large scale convective cells are generated, and the air mass is forced to spin in response to the Coriolis Effect. This causes deflection of air masses to the right in the northern hemisphere and deflection to the left in the southern. For storms to sustain themselves, the upward movement of warm water vapor needs to be constantly resupplied or the storm will weaken and eventually fall apart.  The video beelow explain how a hurricane forms and outlines its anatomy:

Video: Hurricanes 101 | National Geographic (2:57)

How a hurricane develops: Hurricane Facts

For a tropical cyclone to generate, the temperature of the upper 60 meters (~200 ft.) of the ocean water must be greater than 26°C (~79°F). In addition, certain atmospheric conditions are needed to drive the formation of convection cell described above. Horizontal shear winds prevent formation; conversely, in conditions with low wind shear, heat and moisture are retained to allow continued development. The building of the tall cumulonimbus clouds associated with a tropical cyclone depends on the deep convection currents extending into the troposphere. The initial anomaly is called a tropical wave, and then with progressive intensification, it is called a disturbance, an investigation (where it is given a number), then a depression, tropical storm, then a hurricane. This is explained in the following video:

Video: The Basics of Hurricanes and Tropical Weather Forecasting (8:07)

Anatomy of a Hurricane

There are distinct stages of formation that vary greatly from storm to storm. As the pressure drops in the center of the storm, the winds that rotate around the center increase. Narrow cloud bands form, spiraling inwards. The center of the storm, or the eye, is where the lowest pressure is found. The eye wall at the edge of the eye has some of the strongest winds and intense thunderstorms, but the eye itself is characterized by calm. The hurricane-force winds may extend out from the eye for 300 km (~186 miles). The strongest winds occur towards the right-hand side of the center in the direction of the cyclone’s path, so a storm moving north will have the strongest winds in the northeastern quadrant.

Hurricane Tracks and Forecasting

Hurricane movement is guided by surface winds. As we will see in the examples given, the Atlantic hurricanes travel west or northwest across the Atlantic and then recurve to the north and then northeast. This curvature is dictated by the Coriolis effect, which is caused by the Earth’s rotation. This pattern also occurs in the northern Pacific. Although these are predictable patterns, each storm has a unique path and there is great variation depending upon the atmospheric conditions near the storm, which act as steering forces. As we will see later wind movements are a function of atmospheric pressure, with storms basically moving around high pressure systems and towards low pressure systems.

Nevertheless, the patterns made by the historic tracks seen in the animation below show how the storms generally follow certain rules. This predictability aids in forecasting the paths using satellite data and numerical modeling.

Video: Hurricane Tracks Animation and Cumulative Map (0:14) (Video is not narrated.)

The cyclone’s interaction with the ocean’s surface has an effect of reducing the surface temperatures of the ocean. Once the storm approaches land, it encounters shallower water and begins interacting with coastal features. Friction and loss of the warm water “fuel” remove energy from the system, and it will dissipate once over land. It is at the ocean-land interface that the storm surge, which builds with the storm in the ocean, creates a tremendous hazard for those living on the coast.

Understanding the impact of storm systems as they come ashore is not straightforward. Although storm systems may have similar size, strength, and movement speeds, differences in their trajectories relative to the shoreline, together with geomorphic features present along the shoreline (i.e., reefs, mangroves, barrier islands, constructed shorelines, etc.), water depth, and timing of tides all have profound impacts on the intensity of damage individual storms produce. As will be seen in the case studies in Module 6, passive continental margins like the Atlantic seaboard, although they have limited risk from tectonic movement, are subject to extreme impacts from tropical storms. It is, therefore, incredibly important for communities located in such settings to not only understand the risks, but also to work to limit and minimize storm impacts on the human landscape as much as is possible while limiting the cost of doing so. Future modules will explore these factors in more detail.

Quick Review

Watch the following two videos for review and answer the Learning Check Point questions to be sure you have understood the material provided.

The following video provides an animation of the 2005 hurricane season, with an excellent review of the conditions required for active hurricane formation.

Video: Hurricanes Explained: How 2005 Was the Perfect Storm (4:56)

This NASA video explains the mechanism of tropical cyclone formation in terms of heat transfer.

Video: Hurricane Heat Engine (2:05)

Take a few minutes to answer the questions below.

Storm surge is the high water generated by the storm’s winds while at sea. The surge is the height of the water over and above the predicted astronomical tide. This is distinguished from “storm tide,” which combines surge and tide. When the storm approaches land, it pushes this elevated water onto the land, with energy levels that cause tremendous damage to human structures and rearrange natural coastal features. It is the most dangerous storm aspect, responsible for perhaps 75% of the deaths associated with tropical cyclones. A large storm surge can penetrate miles inland, destroying property, moving large amounts of sediment, and wiping the landscape clean of vegetation.

As we mentioned above, coastal settings with embayments are particularly prone to high waters from storm surges, which get magnified when they enter a bay or river mouth. Rocky shorelines are less susceptible because these shorelines are often configured with relatively deep offshore bathymetric approaches that do not support the development of significantly high volumes of water in the nearshore region. In the U.S., the largest storm surge ever recorded occurred during Hurricane Katrina in the area of Pass Christian, Mississippi, where the level was increased as it entered several bays, including Bay St. Louis. Combined with wave heights, the storm surge at Biloxi, Mississippi created a high watermark in excess of 30 feet.

Based on modeling using NOAA’s SLOSH (Sea Lake and Overland Surge from Hurricanes) program, geoscientists have predicted the highest theoretical storm surges, and all occur on either the Gulf Coast or the East Coast in areas that are heavily populated and developed. Go to: U.S. Storm Surge Records to read about how first-hand evidence, such as high watermarks, and modeling such as the SLOSH models, can help us understand the potential of storm surge.

Globally, the highest storm surge ever is reported in northern Australia in 1899 during a cyclone. Although the exact height is still uncertain, it is reported to have been in excess of 40 feet. For details, see World Storm Surge Records. In the Indian Ocean, a cyclone produced a surge measured at just over 10 meters (~34 feet) in Bangladesh in 1970. This event produced the largest number of casualties on record for all storms globally, see The 35 Deadliest Tropical Cyclones in World History.

You can use the NOAA Historical Hurricane Tracks server to search for specific storms. See the link below the image in the figure below.

NOAA’s Historical Hurricane Tracks server.

Credit: NOAA: Historical Hurricane Tracks (Public Domain)

Before looking at examples of catastrophic storms, let’s review the ways they are quantified in terms of strength. The Saffir-Simpson Scale was developed in 1971 by civil engineer Herbert Saffir and meteorologist Robert Simpson, who at the time was director of the U.S. National Hurricane Center (NHC).

The scale uses the wind speeds and pressure of a storm to determine its strength. It did not originally take into account storm surge. The modified version of the Saffir-Simpson Scale on HurricaneZone.net attempts to rectify this by assigning storm surge ranges to the scale. Please visit this site to learn about the classification of tropical cyclones (Categories of hurricanes and typhoons).

An abbreviated summary of this modified Saffir-Simpson scale is shown below.

Because storm surge is not well integrated into the Saffir Simpson Scale, it is often under-appreciated for the risk it poses when a hurricane comes ashore. It is the most dangerous part of any coastal hurricane impact and has been responsible for the majority of the deaths that have been recorded as a result of U.S. hurricanes. A good example is found in Hurricane Katrina. Although classified as category 3 upon landfall, Katrina was category 5 while in the Gulf of Mexico. Therefore, the storm surge, at more than 20 ft. fit the category 5 surge classification according to this modified scale.

You may wonder why a storm like Katrina, which made landfall as a category 3 storm, had such a huge storm surge compared to say, Harvey, which came ashore as a category 4 storm. When a hurricane is approaching a shoreline, the communities in its path need good information about what to expect. But surge predictions are tricky.

Refer back to the Saffir-Simpson Scale. These are estimates that are not 100% reliable because there are many factors determining the height of a surge. They include:

• the size, intensity, speed, and angle of approach of the storm itself;
• the width and slope of the offshore shelf and the slope of the shoreline itself;
• the shape of the shoreline and coastal features present.

The intensity (wind speed) of a storm is directly related to the storm surge – with the relationship shown in the Saffir-Simpson Scale. The speed of a storm has an impact on the size of the surge, but it is not a simple relationship. A fast-moving storm can generate a higher surge, but when a slow-moving storm pushes a surge into a coastal bay or other enclosed water body, it can cause the surge height to magnify. A large storm (in terms of diameter) can produce a larger surge than a smaller storm because the winds affect a larger area of the ocean. The communities along the Gulf Coast are keenly aware of another feature of hurricane storm surges: The greatest surge occurs in the northeast quadrant of the storm, to the east of the eye of a northward moving hurricane. Hence, Bay St. Louis, Mississippi received a greater storm surge than New Orleans in Katrina.

If the offshore continental shelf is wide and gently sloping, the storm surge will be greater than if the shelf is narrow and steeper. If the land also has a very gentle gradient, then there will be little to stop the storm surge from flooding far inland. This is the case on the Louisiana coast as well as other locations along the Gulf coast. This topic will be revisited in Module 8. Narrow inlets along a coastline will tend to magnify a storm surge as the water is funneled into the opening and “piles up”. This was evident on the Mississippi coast when Katrina’s storm surge came ashore in 2005. See the SLOSH model animation below. Here, the surge pushed into Bay St. Louis with an almost 30 ft storm surge. Conversely, features such as offshore barrier islands can act to reduce the surge height before it comes ashore, although these features take the brunt of the energy of the surge, resulting in massive amounts of erosion.

Hurricane Tracks and Forecasting

As we will see in the examples given, the Atlantic hurricanes travel west or northwest across the Atlantic and then recurve to the north and then northeast. This curvature is dictated by the Coriolis effect, which is caused by the Earth’s rotation. This pattern also occurs in the northern Pacific. Although these are predictable patterns, each storm has a unique path and there is great variation depending upon the atmospheric conditions near the storm, which act as steering forces.

Nevertheless, the patterns made by the historic tracks seen in the animation below show how the storms generally follow certain rules. This predictability aids in forecasting the paths using satellite data and numerical modeling.

Video: Hurricane Tracks Animation and Cumulative Map (0:14) (Video is not narrated.)

The cyclone’s interaction with the ocean’s surface has the effect of reducing the surface temperatures of the ocean. Once the storm approaches land, it encounters shallower water and begins interacting with coastal features. Friction and loss of the warm water “fuel” remove energy from the system, and it will dissipate once over land. It is at the ocean-land interface that the storm surge, which builds with the storm in the ocean, creates a tremendous hazard for those living on the coast.

Predicting the path and intensification of hurricanes can be very difficult. As we have learned earlier, there are many factors that control how a hurricane moves, and determining whether and by how much it will intensify is also complex. These variables include sea surface temperature, steering winds, atmospheric pressure, and several others. Because of this complexity, forecasting is now always done with atmospheric models that have become far more capable and accurate in recent years. There are dozens of models that are used in forecasting, and they don’t always agree. That is why hurricane forecasts have a cone of uncertainty. Moreover, different factors impact the storm path and whether it intensifies. The National Hurricane Center in the US compiles these model forecasts, and collectively they are called Spaghetti Diagrams because of the long, closely parallel paths of the different models. The models are used to build a cone of uncertainty that shows the range of the possible storm forecasts.

So in summary, hurricanes' paths are steered by winds which are a function of atmospheric pressure systems. Intensification is impacted by wind shear as well as ocean temperature. Satellite images of a hurricane help determine whether the storm is intensifying or weakening.

In Module 2 we briefly discussed extratropical storms (Northeasters and fronts) and their destructive power. Here we learned an important distinction: Although extra-tropical storms are typically smaller and less powerful than tropical cyclones, they are much more frequent, so their cumulative impact on a coastline can be more significant. We will now take a closer look at these types of storms, also referred to as “Cold Core” storms.

Extratropical storms, otherwise thought of as “cold core” storms, are generally produced outside of tropical regions. In contrast to tropical storms produced by an uplift of warm moist air masses fueled primarily by evaporation of warm waters, extratropical storms are formed when cold air masses interact with warm air masses on land or at sea. As these bodies of cold air collide with warm air bodies, discontinuities (that is, weather fronts) form. As the fronts mature and strengthen, the denser, drier cold air masses move underneath the more buoyant warm air masses and help force the warm air to rise. As a result of this rising air leaving the surface, low-pressure systems, called cyclones, develop and draw air (i.e., wind) into the low-pressure center. In the Northern Hemisphere, the winds of these cyclonic systems deflect to the right as a result of the Coriolis Effect. The opposite is true in the Southern Hemisphere. As a result, cyclones have a counterclockwise rotation in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere. As the warm air rises in the atmosphere, it cools and releases its potential energy as sensible heat, thereby raising the temperature, making the air more buoyant, and consequently fueling a more intense upward movement of air, which further lowers the pressure at the surface, intensifying the storm. At the same time, the water vapor in the rising air condenses, turning into cloud droplets, and they subsequently become precipitation. Through these positive feedbacks, temperature, pressure, and humidity (moisture) gradients between lower and upper-level layers of the atmosphere help fuel the continued development of high winds and extreme types and volumes of precipitation. Most extratropical storm systems are neither large nor intense and produce modest winds and precipitation totals, but when conditions are right, they become quite powerful and extraordinary in their scale and impact. Blizzards, nor’easters, and thunderstorms formed along frontal boundaries are examples of powerful extratropical storm systems.

The storms discussed above occurred on the West Coast of the U.S., but what about similar storms that form on the East Coast? When similar storms form along the eastern seaboard, they can often grow into monster storm systems that have wide-ranging impacts. When they do develop, they are termed nor’easters. In most storm formation scenarios, warm moist air masses originating from the Gulf of Mexico move north and east. They then collide with cold fronts originating from Arctic Canada that push south. In many cases, the warm air masses form ridges of high pressure that form on either side of a cold air trough. When the air masses collide, low pressure develops as the warm air mass on the leading side of the trough is forced upward.

Like tropical cyclones, these storms can actually intensify when they are fueled by warm water. In the case of nor’easters, when the low-pressure system moves over the mid-Atlantic coast, they often intersect air masses fueled by the warm Gulf Stream. This warm water produces moisture-laden air that rises rapidly when displaced by the denser cold air and helps to strengthen the convective uplift. By pumping additional warm, moist air into the atmosphere, these storm systems can become stronger, often with gale-force winds, and intensive precipitation. As most of these storms occur in the winter, they often result in significant snowfall inland and have intensive coastal impacts with high waves and intensive erosion. Each year, nor’easters can be relatively minor or can be very severe.

Video: What is a Nor'Easter? (2:30)

This video helps explain how these types of storms form.

Video: Satellite View of February Nor'easter (0:45)(No Narration)

In this silent animation produced by NASA’s Goddard Space Flight Center using NOAA’s GOES satellite, you can see how a nor’ easter formed in February 2013 when New England and much of the U.S. Northeast was impacted by heavy snowfall, ice, and high winds.

By carefully watching this video, you can follow water vapor that originates in the Gulf of Mexico and a series of cold fronts that move east from the central U.S. As this water vapor moves off the mid-Atlantic, the air masses collide and intensify into a well-organized counter-clockwise rotating low-pressure cell that brings much of the moisture at high altitude back over land from the northeast. As the center of circulation is located along the New Jersey coast, the rotation brings intensive winds out of the northeast to the New England coastline.

This short lab will help you hone your skills for predicting whether a hurricane is likely to develop or not, and where it might go. As we have learned, there are many factors that control whether a storm develops and its ultimate path, but here we will focus on sea surface temperature (SSTs), wind shear, and pressure. Here are the basics: for a storm to develop you need some type of disturbance, SSTs above 79^oF (26^oC), and for it to gain momentum you need low wind shear. Storms are steered by winds, this essentially being “deflected” or moving around areas of high pressure including the Bermuda high and towards troughs of low pressure. As we’ve said, it's more complex than that, but these are the nuts and bolts.

To hone your skills, we have set up a few practice questions. Go to Module 5 Lab (Practice). You can take this practice quiz as many times as you like and ask us questions if you don’t understand something. When you are ready, go to Module 5 Lab (Graded) to answer questions for credit. You will only get one chance at them. Again, this is a fairly short and simple exercise, but we truly hope it will help you predict the next storm!

We hope you have learned more about how storms form and the forces that control their movement. And why they can be so difficult to forecast. In addition, we hope you understand the elements of storms that cause damage in addition to wind: massive amounts of rain and storm surge. You'll be learning about some incredible storms and the damage they caused in the next module. We hope from now on, you'll stay tuned in the summer months to the National Hurricane Center.

They also have a great free app you can access on your phone through the App Store.

Reminder - Complete all of the Module 5 tasks!

You have reached the end of Module 5! Double-check the Module 5 Roadmap to make sure you have completed all of the activities listed there before you begin Module 6.

• Students will continue to develop the fundamental geospatial skills and concepts needed to assess the coastal processes and hazards discussed in this course.
• Students will develop an understanding of the relationships between the atmosphere and hydrosphere that result in the development of cyclones.
• Students will consider current shoreline processes in the context of cyclones and past and present evolution of coastline morphology.

Learning Objectives

By the end of this module, students should be able to:

• describe the atmospheric conditions that are required for the formation of tropical and extra-tropical cyclones;
• analyze case studies of how coastal systems are impacted by geologic and climatic hazards such as cyclones;
• investigate geomorphological changes that result from cyclones.

Module 6 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

Hurricanes are very personal for us. Dinah lived through the calamitous Hurricane Katrina in New Orleans in 2005 and Tim was literally a first responder after Hurricane Andrew struck Miami in 1992 and lived through the much less severe Hurricane Fran that hit North Carolina in 1996. We start this module with these personal stories before moving to describe several of the most significant recent storms in detail. Each storm has lessons to tell about how our society deals with national disasters, what storms will be like in the future, and what we need to do to prepare for them.

Dinah’s Experiences

Years of evacuation preceded Hurricane Katrina in New Orleans. These included Hurricane Georges, Hurricane Ivan, and others for which New Orleanians packed up their cars and headed to wherever they had a safe haven. If you did not have relatives and friends in places within driving distance that were safe, or you didn’t have a reliable car, you stayed. I had packed up my daughter and dogs and headed with friends to places like Lafayette for a three-day trip and then returned to an unscathed city on several occasions. Hurricanes on track to impact New Orleans had a habit of making a northerly turn as they approached the Mississippi River delta and hitting the Mississippi coast instead of Louisiana. We were all armchair hurricane experts by the time Katrina entered the Gulf. At the University of New Orleans, I worked with a network of coastal scientists, some of whom were actual hurricane experts, including my boss, the late Dr. Shea Penland, who was a renowned coastal geomorphologist and director of the UNO Pontchartrain Institute for Environmental Sciences. He had made a fateful prediction in the Scientific American Magazine the year before that it was just a matter of time before a storm surge would overwhelm the flood protection system and devastate New Orleans. I clearly remember our staff meeting on Friday, August 26, 2005, in which we discussed the storm entering the Gulf, and the need to retrieve boats and other equipment from coastal locations. It is hard to fathom now, but three days later, on Monday, August 29, Hurricane Katrina made landfall in Louisiana. The adrenaline-driven scramble to prepare for the impending storm is now a blur, punctuated by flashes of memories of moving computer equipment away from windows, moveable objects from yards, and conferring with elderly neighbors about their plans for leaving. After several days of exhausting preparation, during which I observed a general lack of urgency in New Orleans, I was ready to evacuate. I had noticed less boarding up than for Hurricane Ivan in 2004, and many acquaintances seemed almost blasé – I so clearly remember a rowdy crowd spilling from a daiquiri bar onto the street as I made my way home on Saturday night. There was a certain amount of bravado in not leaving. But then there were so many people who did not have any good choices, being without reliable transportation or no place to go to or being too frail or sick to choose for themselves. Neighbors and extended family formed support networks, but these efforts could not avoid the coming specter of tens of thousands of people seeking shelter in the Superdome and Convention Center after the storm flooded the city. The city neglected to plan a mass evacuation by bus prior to the storm.

I evacuated with my two dogs and a few belongings on Sunday, August 28th at around 4:30 am. I heard the Mayor of New Orleans announce the MANDATORY evacuation on the radio as I drove. This was way too late. Residents would have to at least have made their plans and be packing up to leave by then. Many already had, because we were so well trained to do so, but many were too cynical or had no choice but to stay put. Others did not want to leave their property unoccupied. But we were not uninformed. I took back roads to avoid the crush on the interstate. People reported taking four hours to reach Baton Rouge, a trip that usually takes a little over an hour. This was despite the use of contraflow on the interstate highways leading away from New Orleans and the Gulf Coast. I finally arrived in the small town of Walker, to the east of Baton Rouge, where my colleagues had been gathering. There, our business manager, Karen Ramsey, and her husband had a home that could accommodate quite a few people. But I arrived too late - there was no room at the inn. I traveled on to share an off-campus LSU dorm room in Baton Rouge with my daughter, literally timesharing her bed, with the dogs sleeping underneath. The complex of student housing, which amazingly still had power, quickly filled up with evacuee families. I wasn’t sure where I was going to stay for the longer term but, I had enough friends in Baton Rouge that I was soon able to find kind people with a room where I could stay with my dogs for several weeks. The population of Baton Rouge exploded with displaced New Orleanians, which caused some tension. This was happening in cities across the South as half a million people had to find somewhere to stay.

The thing to remember about New Orleans is that it is surrounded by flood protection structures including levees and floodwalls, and the draining of the wetlands upon which the city was built has resulted in significant subsidence of the land elevation so that 50% of the land area within the flood defenses sits below sea level. The other thing was that in 2005, the levees and floodwalls, designed and built after Hurricane Betsy in 1965 to protect the city from a category 3 storm surge, were now almost 4 decades old. They were worn, had subsided, and had many flaws. We had been warned repeatedly via so many information channels that this was a recipe for disaster. The disaster slowly unfolded on Monday morning, but at first, many residents in New Orleans were unaware that it was happening. The cell towers had toppled with Katrina’s winds, so only landlines still worked. I was able to call my ex-husband before my cellphone went kaput on Monday morning. He had chosen to stay and was nonchalant at that point, oblivious to the encroaching floodwaters, which had by then broken through the flood defenses in many places, and the “bowl” of the city was filling up. I remember saying I thought it was a matter of time before the waters reached his house, and that is what happened. The real misery began after the storm itself had passed and moved north. People were trapped on rooftops or were wading or floating on debris through floodwaters trying to find refuge, with children, pets, and belongings in tow. It was blazing hot. Meanwhile, I was in the safety of Baton Rouge just watching in horror and feeling helpless and suffering from survivor’s guilt. I was able to travel to deliver cash I had collected before leaving New Orleans to a friend (how do you access your New Orleans bank account when everything is broken?) and go to a hotel lobby in a small Southwest Louisiana town to use their computer to add texting to my cellphone account so my daughter could locate her father. Not many people were using texting in 2005 and with cell towers down, for some reason, texting worked but calling did not. A family I talked to at the hotel were from St. Bernard Parish, southeast of New Orleans and devastated, and they did not know if members of their family were alive or not or how to reach them. My daughter was able to locate her dad who had made it out of New Orleans with dogs and cats; and she picked them all up in Baton Rouge. Many people and pets were not so lucky. Many ended up in shelters far from home and loved ones could not locate them. Children were separated from parents and elderly grandparents were lost in the chaos. Helicopters continually plied back and forth between Baton Rouge and other locations and the city, on rescue missions.

My first trip back into the city was on September 16. I clearly remember the unforgettable, indescribable smell as we got close to the UNO campus. My colleagues and I were headed there to pick up work vehicles and equipment to bring back to Walker to set up a temporary office for the Pontchartrain Institute. We needed a special permit to enter the city at that point. Although the city had been drained of floodwaters by then (using pumps shipped in from around the world), the entire population of over 480,000 had forcibly been moved out (by 2006 only about half had returned). We stopped to check on colleagues’ houses which had flooded to the roof and the contents jumbled around inside, covered with stinking mud. Dead fish lay in the streets. There was no power, so we had to feel our way up hot, dark stairwells to our offices where mold was already growing, making breathing hazardous. The National Guard had used our offices as a triage center and the campus was a processing center where people were shipped out to shelters. It was quite surreal. I remember looking out of a third-floor window at the downtown skyline and thinking how normal it looked from there, while the city as a whole was wrecked. The UNO campus sits on slightly elevated land on the shore of Lake Pontchartrain, next to the London Avenue drainage canal in which the concrete floodwalls had been breached and Lake Pontchartrain had poured into the low lying Gentilly neighborhood. It is worth repeating that 80% of the city had gone underwater and approximately 1,000 people had died (the exact number will never be known). My old neighborhood, where I had recently sold my home of 14 years had been deeply flooded. The neighborhood where was renting an apartment was fine because it was in Carrollton, an old part of the city on the natural high ground built by the Mississippi River. But on this occasion, I was not allowed to go to my apartment. We were there strictly on official business and we loaded up the trucks and drove back to Walker.

I was very fortunate to still have a job and an intact home, and eventually, we set up a place to work for a year in Walker. Our offices on the UNO campus were closed off for that duration. The fall semester, which had been so rudely interrupted by Katrina, continued in some fashion with online classes, but mostly it was a wash. Students scattered to other institutions to try to continue their studies, only slowly trickling back as accommodation was hard to come by. Residents of the city were able to return neighborhood by neighborhood in October, about six weeks after the storm. Most had to commute from outlying areas to begin work on their wrecked homes (remember the count of flooded houses in New Orleans alone was 134,000). The traffic was bumper to bumper from Baton Rouge to New Orleans with materials for rebuilding being shipped in. Recovery had to start from scratch. At first, the power supply was spotty and the infrastructure sparse, with few services such as groceries, doctors, etc. It was very hard to imagine how the city could possibly recover. I returned in November, having exhausted accommodation options, but still had to commute 1-2 hours to Walker to go to work.

One of the tasks I had in my varied job as a research associate after Katrina was to accompany a photographer who was working on documenting the aftermath of the storm. This took us to many outlying neighborhoods in St. Bernard parish as well as all over New Orleans. Shattered neighborhoods were silent and empty. Dried mud covered everything. Cars sat atop fallen roofs and household items and children’s toys were strewn across the landscape. This was before rebuilding began in earnest, but signs of activity were here and there. Homemade yard signs and sculptures made from the debris were evidence of the enduring humor of the south Louisiana people. Later the sounds of hammering and voices of the thousands of volunteers and day laborers who poured in to help rebuild filled the eerie silence. It was to be a long and difficult road to recovery and one of the many details that we could not fathom before the impending disaster happened, despite all the warnings. Year by year, for the first decade, New Orleans slowly became a fully functioning community. The levees were rebuilt and reinforced. The scars are still clearly visible with swaths of vacant land where there were once neighborhoods and shopping centers, but lives have been rebuilt and the city has moved on.

Hurricane Katrina Damages

Tim’s Experiences

I was literally one of the first people into Miami after Hurricane Andrew roared ashore on August 24th, 1992. I was on my way down to South Florida to fly to Cuba for fieldwork when I heard about the storm approaching. I had a seat on a charter flight, very difficult to obtain so there was no backing out or changes possible. The storm accelerated in the couple of days before slamming into southern Dade county leaving folks little time to prepare. I had lived in South Florida in the late 1980s and grew used to the days-long wait as storms approached, store shelves emptied out, windows were boarded up, only to see the storm veer off or weaken at the last minute. So it was easy to see how everyone was a little complacent in 1992.

Andrew formed over the Atlantic on August 16th, 1992 but very rapidly gained strength on August 23rd over the Bahamas. The storm made landfall in the early morning hours of August 24th near Homestead FL as a category 5 storm with sustained winds of 165 mph making it one of the strongest storms ever to make landfall. Gusts were over 175 and there were reports of gauges on boats recording 195 mph. The fact that the storm intensified so fast as it approached also increased the shock of the damage.

I packed my truck full of coolers, water, camping gas canisters, canned goods, and tarps, left Chapel Hill in the early afternoon of the 24th, and arrived in Miami in the early morning hours of the 25th. One good thing about a hurricane is the cops let you speed, I made 862 miles in just over 10 hours! The morning brought into focus the extent of the damage, but also how most of the heavily populated central and northern part of Miami had minimal damage and had really dodged a bullet. If the storm had gone just 10 miles further north the cost would have been far, far higher. But that was of no consolation to the communities that got hit, and hit very hard. In Kendall and South Miami, where I used to live, and in the Homestead, Cutler Ridge and Perrine areas the damage was unlike anything I had ever seen. It was like Andrew had mowed down the whole landscape, houses included. Almost every home had extensive roof damage, windows had blown out, and houses and pools were full of debris and sand. Some areas were worse than others with whole parts of homes completely destroyed. But the very worst areas were cordoned off by police and inaccessible. Almost every palm tree had lost all of its leaves and palm fronds were everywhere. Roofs of gas stations were now mangled metal and road signs and billboards were flattened. The sun was out and blazing, but power was out everywhere. People were in a daze and told harrowing stories of nights spent in bathtubs covered by mattresses only to emerge to see their homes almost gone. My supplies were happily accepted. I spent much of the next few days nailing tarps to roofs in the blazing sun before leaving for Cuba. It was amazing to leave powerless South Florida and arrive in the relative comforts of the communist country. My Andrew experience left an indelible mark on me, it made me in awe of the force of nature and fascinated by hurricanes and the threat they cause to coastal communities. From then on I became an avid storm watcher, glued to the Weather Channel when a storm was active and to the National Hurricane Center’s website. I’ve seen how sophisticated prediction has become, but, even then, there is still a lot of uncertainty which makes living in a coastal community very challenging in the summertime.

I experienced a hurricane up close, Hurricane Fran in Chapel Hill, North Carolina in 1996, although the storm was very minor compared to Andrew and Katrina. The storm was just turning seaward when I went to bed and the TV forecaster said “looks like we are out of the woods, folks” then the power went out. Imagine the shock then when a 150-foot red oak fell on our tin roof at 2 AM! The noise was deafening and woke me out of a deep sleep. Outside the wind was incredible and all I could hear was the snapping of trees then the boom as they hit the ground, tcshick-thud, tcshick-thud, tcshick-thud, tcshick-thud. They were snapping like matches! It was pitch dark and impossible to see anything and I was terrified (living through a storm is much worse at night believe me!). As I wandered around the house everything looked OK………until water started pouring through the light fixtures and terrified squirrels who came down with the tree and into the house came out of their dazes! Luckily we didn’t have to wait long to see the damage in the daylight, the huge oak tree had cut our roof in two, but fortunately hit the edge of the house so much of it was spared. It could have easily hit me when I was sleeping. Neighbors didn’t fare as well, whole pieces of houses were lifted out of their foundations by giant trees, people were trapped in their bedrooms, and cars were cut in half. Turns out the damage was done by microburst tornadoes spun off by the storm. Sustained winds in our neighborhood were about 60 mph but the tornadoes were over 100 mph.

After the storm came weeks-long rebuilding effort, eight hot days with no power, the constant buzz of chainsaws through the daylight hours, nights of curfew, haggling with the insurance companies. Within months things were back to normal, but the psychological scars were there for years, sleepless nights when thunderstorms came, worrying about which trees could fall and what direction they would fall in. The worrying would increase in summer as storms approached. But my Fran experience was nothing like what people who have lived through category 4 and 5 storms have gone through. And specifically what Dinah went through during and after Katrina.

Hurricane Andrew Damages

Hurricane Andrew was a wake-up call for the US. Hurricane Hugo in 1989 had caused a massive amount of damage in Charleston, SC as a result of wind and a massive storm surge up to 6 meters (20 feet). But Andrew was the first major hurricane to hit a major metropolitan area in a long time, and it exposed glaring weaknesses in preparedness, especially building codes. The storm narrowly missed downtown Miami and Miami Beach, which would have led to truly catastrophic damage and many more fatalities. However, the areas that took direct hit including South Miami, Perrine, Cutler Ridge, and Kendall had seen rampant development over the preceding ten years so the damage was still devastating.

Hurricane Andrew

Andrew came ashore in the early morning of August 24, 1992, near Homestead with sustained winds of 165 mph, gusts of 177 mph and a storm surge up to 5 meters (17 feet). Fortunately, the storm had a very rapid forward motion of 16 mph so the maximum impact didn’t last that long, and the storm was quite compact, however, Andrew’s winds still wrecked a narrow trail of havoc. In 1992 development in South Florida was booming. Much of the western part of the Miami metro area is land that has been reclaimed from the Everglades over the past half-century, one of the most extensive and radical reclamation projects in the world. The Everglades is the largest subtropical wetlands in the world, aptly called “a sea of grass” by the famous naturalist Marjorie Stoneman Douglas. The wetlands naturally drain to the south, but this was changed in the 1950s to 1970s when drainage canals were constructed, supposedly to control flooding from hurricanes, and diverted the water to the west and east. The resulting changes to the natural landscape were nothing short of disastrous. Rapid urbanization has covered large areas of the former Everglades with concrete leading to flash flooding in storms, which undoubtedly made damage from Andrew more intense. As devastating storms like Andrew and sea level rise (Module 3) threaten coastal parts of South Florida, we are constantly reminded that the Everglades were not meant to be urbanized.

The other lesson from Andrew had to do with building codes. I remember from my time living in Miami in the late 1980s numerous sprawling developments with large, wooden framed and wood and plaster sided homes packed close to one another on meandering streets with pools, clubhouses, and other amenities. Country Walk was one of them, a particularly massive development of wood-framed houses, which now lives in Andrew infamy. Construction in Country Walk by the company Arvida was particularly shoddy and houses fell like match-sticks in Andrew. The damage was just catastrophic. Residents told harrowing stories of windows and doors exploding, walls toppling over and popcorn ceilings, and whole second stories collapsing. Many people sheltered in interior bathrooms only to have the roofs collapse on them. Almost no homes were left with roofs after the storm. 95% of the 1700 homes in Country Walk were completely destroyed. The difference between Country Walk and neighboring developments with more solid construction was stark. Most residents of Country Walk collected their insurance money and moved away, often out of state.

Investigations of Country Walk found gables that were not braced or connected to roofs, plus poorly connected trusses, sheathing, strapping, and tie beams. Pre-construction plans on models were not checked by structural engineers and inspectors were found to have cut corners because of heavy workloads and many were just doing drive-bys instead of inspecting homes closely.

Video: Hurricane Andrew - Tamiami Airport/Country Walk (19:37) (Video is not narrated.)

This video shows the devastation of Country Walk.

Country Walk was not the only development with severe damage from Andrew. The storm basically exposed all poor construction. In light of this damage and with a view towards the stronger storms of the future, South Florida counties instituted very strict building codes. Code in the so-called “high-velocity hurricane zone” where “basic wind speed” (a measure of the recurrence of strong storms) is over 180 mph, including Miami-Dade and Broward counties, requires new construction to be a wind-resistant design, including windows, doors, and eaves. Hurricane shutters are mandatory in all parts of the state where the basic wind speed is over 120 mph. The performance and installation of shutters are very strict. However, regulations other than shutters vary from area to area and are constantly under attack from the construction industry, so who knows what the future will bring. One last aspect of living in a hurricane-prone area is crazy expensive insurance. Rates for insurance depends on the number of hurricane improvements a home has but can be up to $8,000 a year for a home valued at $150,000!

Video: Hurricane Andrew - Miami-Dade County, Florida - August 23-24, 1992 (8:18) (Video includes people talking, but is not narrated.)

This video summarized the power of Andrew.

Video: Then and Now: Scenes from Hurricane Andrew (11:39)

This video provides a more personal glimpse of the impact of the storm.

There is no doubt that South Florida is much better prepared than it was in 1992. And there is also no doubt it will need to be.

Hurricane Katrina’s historic impacts on New Orleans and Gulf Coast communities in Louisiana, Mississippi, and Alabama in 2005 serve as an important reminder of the destructive forces of hurricanes, most notably from storm surge. Katrina’s storm surge was so destructive that most gauges broke during the storm, making it difficult to get actual measurements. High-water marks in eastern Louisiana and western Mississippi indicate that the maximum surge was close to 9 meters (30 ft.).

In New Orleans, the failed levee systems allowed billions of gallons of seawater to flood 80% of the city, as well as some suburban areas. The mayor called for a mandatory evacuation approximately 24 hours before landfall. This was not enough time for many people to make necessary plans, and a large portion of the population of New Orleans was living in poverty and had no means of transportation, while others did not heed the evacuation order for a variety of other reasons. After the initial partial evacuation prior to the storm, the entire population eventually was evacuated from the city following the flooding. For many families, the evacuation dragged into a long-term or permanent situation because they had no home or jobs to come back to. Tragically, families were dispersed, or family members lost. Meanwhile, outside the levee system, there were areas that were completely destroyed, especially to the east of New Orleans and the Mississippi Gulf Coast communities from Bay St. Louis to Biloxi. Katrina will have lasting effects on these communities for decades to come. So, how is it that this storm became one of the most significant global storms in a century?

Scientists from NASA's Goddard Space Flight Center produced an excellent short video (3:03), "Katrina Retrospective: 5 Years Later," that explains many details of the storm’s development and path. Data from numerous weather satellites were compiled to produce these magnificent 3D animations that illustrate exactly what happened before, during, and after the storm. In the video, you will notice the role of warm surface waters in the Gulf of Mexico as they contributed to increased rates of atmospheric uplift, which resulted in strengthening the storm. You will also see how the bands of precipitation moved across the region and the distinct wind patterns that moved the storm over Florida, out into the Gulf and eventually steering it right toward the eastern tip of the boot of Louisiana, and southern Mississippi.

Video: Katrina Retrospective: 5 Years Later (3:04)

The Times-Picayune newspaper produced an excellent interactive map-based time-series animation of the impact of Hurricane Katrina as it came ashore. Anatomy of a flood: How New Orleans flooded during Hurricane Katrina tracks the flooding from levee and floodwall failures as they happened. Each scene includes pop-up dialogue boxes that will guide you through the storm. As you work through the scenes, play special attention to the areas that became flooded (shaded in blue) and the areas where levees were compromised and breached, either due to poor construction and failure or surge levels that overtopped them. Note that the water flowed into the portions of the city that lie below sea level and filled the shallow “bowl” with up to 15 feet of water. In the end, the only areas that sustained little, or no flood damage were located on the natural levees of the Mississippi River or the artificially-created higher ground near Lake Pontchartrain (location of the University of New Orleans).

The storm made its second landfall at Buras, Louisiana (it had already made landfall in Florida before entering the Gulf and strengthening). After crossing the Mississippi River bird’s-foot delta and entering the shallow bays including Lake Borgne in Louisiana and Mississippi Sound near the state line with Mississippi, it made its final landfall near the state line and delivered its historic storm surge to the coastal areas of both states. Water was pushed into the shallow bays, including Lake Pontchartrain and Bay St. Louis, with disastrous consequences. The storm left a trail of destruction, the magnitude of which is hard to imagine without seeing it for yourself.

New Orleans and the low-lying communities to the east that took the brunt of Katrina’s storm surge were essentially crippled for months. It took weeks to pump the water out of New Orleans, as all the pumps that usually drain the city were damaged by the flooding. Pumps were brought in from around the world to drain the city. All that remained of some communities were concrete slabs and pilings. The cities, including the entire city of New Orleans, were without basic services such as power, water, and sewage treatment. Without these utilities, the residents could not return to their homes. Many stories are still told of survival and heroic rescue efforts, as well as people managing to survive by camping out in their wrecked properties during the sweltering September heat following the storm.

Sandy, technically Superstorm Sandy because it merged with another low-pressure system before making landfall in the US, was the largest hurricane ever reported with a diameter of 1400 kilometers (1000 miles)! The storm is known for the damage it inflicted on the New York City region, costing a total of $65 billion. It was notable for two main reasons in addition to its size: first, because it was such a late storm, making landfall on October 29th, 2012, and second because it traveled so far north of typical hurricane country before hitting land.

While a hurricane, Sandy inflicted massive damage in Jamaica, Haiti, the Dominican Republic, and Cuba. In Haiti, the storm was especially destructive and responsible for at least 50 deaths. Sandy had a northerly path and after crossing Cuba and the Bahamas, the storm went out over open waters for several days before taking that dramatic left turn due to its interaction with the low pressure and slamming into the New Jersey coast near Atlantic City.

Coastal communities had plenty of time to prepare. New Jersey forced mass evacuations in low-lying areas, and New York City closed bridges and tunnels and covered subway openings. Sandy’s winds at landfall were 80 mph with gusts up to 90 mph, but most of the damage was done by the storm surge, which measured up to 3 meters (9 feet) in New Jersey and 4 meters (14 feet) in Lower Manhattan. Some areas received a foot of rain. The surge flooded city streets and the subway, including traffic tunnels under the river. Raw sewage was also released into city streets and tunnels. Most of New York City lost power for days. Flooding also occurred along the waterfront on the New Jersey side, with devastating flooding in Jersey City and Bayonne. The New Jersey shore bore the brunt of the damage, with whole towns ravaged by the storm. Close to 350,000 homes were damaged and 22,000 permanently destroyed. This destruction was largely flooding, with wind damage at the shore. Significant beach erosion occurred with on average 9 to 12 meters (30 to 40 feet) of shoreline removed by the storm and Sandy carved new temporary inlets along the shore. Up to a meter (4 feet) of sand was dumped on barrier island streets. Piers collapsed into the ocean. The damage was so extensive in some locations that residents were not allowed back for months. In all, 24 states were impacted by Sandy and there were 71 deaths in nine states. A total of six million people were without power right after the storm. At the time it was the second-costliest hurricane (after Katrina) but has now been surpassed by Harvey and Maria.

Hurricane Sandy

These videos show the damage after Sandy

Video: Hurricane Sandy: As It Happened (7:40)

Video: Most dramatic footage of Superstorm Sandy (3:15)

There are many lessons from Sandy. The New Jersey coast is one of the most developed shorelines in the world, with a booming real estate market. The shore has been developed since the 1940s, originally with small and simple family cottages. However, over the last 20 years or so, small homes were bought out in many areas, bulldozed, and large luxury mansions were built in their place. The shoreline contains billions of dollars of expensive homes, often built too close to the shorefront. As we discuss in Module 10, a lot of the blame for this overdevelopment rests with federal and state governments, who resisted passing sensible flood control laws numerous times. This failure resulted in development in areas that flood frequently. The lack of flood control was exacerbated by the National Flood Insurance Program that repeatedly bailed out homeowners, local governments, and the state. The program is supposed to include controls over where rebuilding can take place, but regulation has been loose. Today, NFIP covers 70-100 percent of rebuilding after hurricanes. Environmentalists and others have pushed for much stricter regulation and an end to bailing out homeowners who build in risky locations, but developers and the construction industry have won out (see more detail in Module 10). These failures resulted in homes rebuilt in harm’s way, in some cases multiple times. Environmentalists warned about the devastating impact of a Sandy event for many years, and the storm proved them right. However, once again, the government paid for everything after Sandy!

Extensive damage in New York City was also a wake-up call. Low-lying downtown Manhattan and the waterfront on the New Jersey side of the Hudson River contains some of the most coveted real estate in the world and is a global financial center. Sea-level rise over the coming decades will make the area even more vulnerable to storm surge, with potentially truly devastating financial implications. For this reason, Sandy inspired renewed discussions about a major investment in flood control that would protect Lower Manhattan and the New Jersey waterfront from storm surge in a future Sandy. There has been considerable planning into what this structure might look like with the most extreme cases involving 8 kilometers (5 miles) of concrete and steel surge “gates” extending from New Jersey all the way to Long Island across the harbor and another gate along the west of Long Island Sound. Each structure would involve miles of shore fortification at the ends of the gates. The system would cost in excess of $120 billion.

Read the latest on the proposed system here in this New York Times article: The $119 Billion Sea Wall That Could Defend New York … or Not

The final lesson from Sandy is that climate change will cause powerful hurricanes to move further north and extend the season into October. It is still debatable whether Sandy was a result of climate change, though the Atlantic waters were warm unusually late in 2012. The New York metro area and the New Jersey shore have seen their share of powerful hurricanes, and Sandy may just have been a late-season anomaly. However, it is certainly reasonable with climate change to expect earlier and later storms and for stronger storms to make landfall further north. The large northeastern “megalopolis” extending from Washington DC to Boston and including Baltimore, Philadelphia, New York City is home to some 50 million people with $3.6 trillion in economic output per year. Sandy likely foreshadowed the future and this region better prepare for the eventuality of more large storms.

Before we start, remember a typhoon is the same as a hurricane but in the western Pacific Ocean while a hurricane is in the eastern Pacific and Atlantic. We choose to discuss Typhoon Haiyan (also called Yolanda) because it was the most devastating tropical storm of the last century in terms of damage and death toll. The storm was also one of the most powerful ever with sustained winds of 195 mph and gusts up to 235 mph when it came ashore on the eastern part of Samar Island in the central Philippines. The category 5 super typhoon had previously hit the island of Palau and would go on to impact Vietnam and China, but it was the Philippines where most of the damage occurred.

Haiyan came ashore on the eastern Samar island on 7 November 2013. Damage on the islands of Samar and Leyte was absolutely catastrophic, but other islands including Cebu and Bohol were hit very hard. On Samar and Leyte a storm surge of up to 5 meters (17 feet) and waves up to 6 meters (20 feet) were recorded and rainfall up to 0.3 meters (a foot) fell in a day. The damage was just terrible in the low-lying Tacloban City where flooding extended up to a kilometer inland and 90 percent of the city was destroyed. Many people in Tacloban drowned in rapidly rising floodwaters, cars were tossed around like match-sticks, and debris was thrown everywhere.

Typhoon Haiyan

In all, more than 7360 people died, 27,000 were injured and 6 million displaced. 1.1 million homes were swept away or destroyed. Tacloban city more than 4,000 people perished. Overall

Please check the following news reports for stunning before and after pictures of damage in Tacloban City.

• Tacloban: a year after typhoon Haiyan
• Philippines: five years after Typhoon Haiyan

In the aftermath getting aid to the millions in need was hampered by the severity of the damage. Water and food were extremely scarce. People had to dig up water pipes just to survive and getting food was even more difficult. The Philippines are used to natural disaster with frequent earthquakes and typhoons, but completely misjudged the strength of Haiyan in the leadup to the storm. Many citizens did not evacuate and remained in low lying areas. For those who did, evacuation centers situated in flood zones turned out to be death traps. Police and medics were also victims so the response was extremely slow and lawlessness ensued. Tacloban was described as a war zone after the storm. Looting was widespread. The city became so dangerous that aid workers were urged not to go. When aid arrived it was poorly distributed, often according to political affiliation. Reports surfaced that food delivered to particular areas was deliberately buried so people could not get access to it. Tens of millions of dollars in aid were sequestered in government bank accounts. Over time international aid flooded in and distribution improved. many places homes were rebuilt from materials damaged in the storm, including battered corrugated iron, old blankets, and tires. But the storm also caused massive resettlement of citizens of the impacted areas as well as relocation away from coastal areas.

Overall Haiyan will be remembered as the most devastating storm of the last century.

Video: Typhoon Haiyan Documentary (20:21)

This documentary portrays the devastation caused by Haiyan.

Hurricane Maria spread wreckage across the Caribbean as she sped toward the island of Puerto Rico. The damage was truly catastrophic in Dominica, where the storm basically flattened scores of homes and flooded others. The photograph below shows just how terrible the damage was there.

Hurricane Maria

Guadeloupe, Martinique, Haiti, and the Virgin Islands also suffered widespread damage. But Maria is almost all about Puerto Rico. The storm made landfall there near Yabucoa on the southeast coast at 10 AM on September 20, 2017. The island was still recovering from Hurricane Irma, which devastated the nearby Virgin Islands and passed to the north of Puerto Rico, but still caused widespread power outages. After Irma, Puerto Rico sent supplies to the Virgin Islands, including water and tarps.

At landfall, winds were clocked at 155 mph, a strong category 4 storm. After landfall winds weakened but the eyewall grew during replacement leading to a larger area of damaging winds. Rainfall caused significant damage, up to 1 meter (38 inches) of rain fell in mountainous areas and much of the eastern half of the island received over 0.4 meters (15 inches). The ground was already saturated as a result of rain from Irma and so this water had nowhere to go. In one notable incident, floodwaters released from the La Plata dam rose up to 4.5 meters (15 feet), caused extensive flooding, and trapped several thousand people. The Guayataca dam was deemed to be at risk of collapse and tens of thousands of people had to evacuate. Flash flooding, mudslides, and landslides were common in mountainous areas, cutting off whole communities. A month after the storm only 640 kilometers (400 miles) of 8000 kilometers (5000 miles) of roads were passable, making getting relief to citizens difficult. Maria destroyed a total of 70,000 homes and damaged up to 300,000 others.

Please take a look at the stunning before and after images from The Guardian, "Puerto Rico six months after Hurricane Maria: then and now" highlighting the impacts and recovery in Puerto Rico. Note that although repairs were completed, most houses pictured have only temporary fixes and blue tarps for roofs.

One of the lessons from Maria was the failure of the power grid. The Puerto Rico power grid was antiquated and extremely vulnerable to a storm like Maria. Lack of funding and years of mismanagement and failure to maintain equipment, combined with damage from previous storms left the grid extremely vulnerable. The national power company, the Puerto Rico Electrical Power Authority (PREPA) was over $7 billion in debt when it filed for bankruptcy months before Maria. Immediately after the storm, the power grid went down for the whole island, leaving 3.4 million people without electricity. Even hospital generators failed. Almost all cell and landline service was down. 90% of the island was still without power a month after the storm, and two months later 1.5 million people were without power. In some places, it took 11 months to restore power! After Maria, the federal government set aside $2 billion to fix the power system, but PREPA has been in bankruptcy negotiations for the last two years, and an earthquake in 2020 again led to widespread blackouts, so problems persist.

Video: Puerto Rico after Hurricane Maria: 'We're American, too, why don't they help?' (9:49)

This video exposes the severity of the poor response to Maria in Puerto Rico

Drinking water was also hit hard by Maria. Up to 50% of citizens had no running water for several weeks. Sewage treatment plants were inoperable for months. Maria wiped out 80 percent of the crop value in Puerto Rico, about $780 million, destroying sugar cane and fruit trees, coffee plants, and vegetables. The storm was particularly hard on trees, ripping off leaves, and stripping bark. One farmer described losing every single one of his 14,000 plantain trees. Row upon row of crops were destroyed. The island imports about 85% of its food, leaving it very vulnerable to a devastating storm like Maria, however before the storm small farming operations were increasing as were local farmers' markets. The loss of croplands combined with the slow response left citizens without food, hungry, and rationing canned goods. After Maria hit, a Federal Emergency was declared and FEMA assistance began with daily relief flights. The Navy deployed numerous ships to help in the relief. However, the scale of the disaster was daunting, hampered by poor communication and difficulty getting assistance to people who needed it, and the government has been criticized for underestimating the severity of the crisis. All in all the storm caused $90 billion in damage.

Estimating the death toll from Maria has been difficult. Officially, 64 people died as a direct result of the storm. However, power cuts, lack of drinking water, food shortages, and the extremely slow governmental response were responsible for far more deaths, especially of people with underlying health problems. But since some of these deaths might have occurred without the storm, the only way to estimate the number is by comparison with mortality rates in previous years. Numerous universities and investigative reporters have made these comparisons, and the estimates are staggering. Up to 3,000 people are thought to have perished in the aftermath of Hurricane Maria, exceeding fatalities in Katrina. Many citizens moved to the mainland US, especially to Florida. Because Puerto Rico is a US territory and citizens pay some federal taxes including Medicare and Social Security, the federal government has been blamed for the slow response , and for not providing more immediate relief and long-term financial aid to the island. The response was so inadequate and the suffering so significant that the international relief organization Oxfam intervened and provided aid to the island. Although the storms, the location, and the nature of the damage were very different and comparisons are difficult, the response (or lack of) to Maria resembled Katrina to many. And because the majority of people impacted by both of these tragedies were minorities, African Americans in the case of Katrina and Hispanics in the case of Maria, there have been charges of environmental racism in both cases. Certainly, the responses to Harvey and Sandy were far superior. Even now, three years after the storm, blue tarps still dot rooftops all over the island, memories of Maria.

Hurricane Harvey came ashore on August 25th near Rockport, TX, with 120 mph winds devastating the small coastal town and flooding the coastal areas with a storm surge, then made another landfall at Holiday Beach as a category 3. By that time, the storm was rapidly weakening to become a tropical depression, and it also was moving very slowly towards the sprawling metropolis of Houston. The storm basically stalled over the city for a few days, and it was rain, not wind, that would become deadly. Harvey has two primary lessons for us: (1) that the warmer atmosphere of today and the future, combined with the predicted slower movement of some storms, can be devastating “rain engines” that dump biblical amounts of precipitation on coastal communities and cause life-threatening flooding; and (2) that particular cities have a great deal more vulnerability than others because of low elevation combined with poor planning. On this note, Houston is a sprawling metropolis of 6 million people that has set itself up for catastrophe.

Hurricane Harvey making landfall on August 25, 2017.

Credit: Harvey by NASA via Wikimedia Commons (Public Domain)

Tropical Storm Harvey was the wettest storm ever to hit the US. The Gulf of Mexico is an incredibly warm water mass, with a temperature of 30 deg C (86 deg F) during Harvey. As we learned in the last module, warm water holds more moisture than cold water and ocean warmth also fuels the energy for the storm. For every 1°C increase in temperature, the atmosphere can hold around 7 percent more water vapor. This may not sound like a lot, but think about this, hurricanes can form when waters exceed 26 deg C (79 deg F) in temperature, so the Gulf of Mexico atmosphere could hold almost 30 percent more moisture than other storms. And because under many conditions the warm atmosphere makes storms move slower, means that devastating rain engines like Harvey will become increasingly common in the future.

Let’s talk about the rain. The rainfall in Harvey has often been called a rain “bomb”, but the term rain bomb is generally reserved for locally intense rainfall over periods of minutes or hours at most. So for Harvey, what we saw was a nuclear rain bomb! It poured for days! Over the five-day period from August 25 to August 29, many parts of Houston received over 30 inches of rain (0.76 meters) with a maximum of 60.58 inches in Nederland, Texas. In total, the Houston region received over 24 trillion gallons of rain. That is enough water to fill every NFL and Division 1 football stadium 100 times over!

Extensive flooding in Houston after Hurricane Harvey

Credit: AMFPhotography via Shutterstock

Flooding of houses in Spring Texas after Hurricane Harvey

Credit: MDay Photography via Shutterstock

The other ingredient for the disaster in Houston was the lack of planning and smart land use. Houston has experienced growth more rapidly than almost any US city, and it has spread outwards rather than upwards. The city now covers an area as large as Chicago, Cleveland, Detroit, and Philadelphia combined! In fact, a large part of the city is built on an ancient floodplain, the Katy Prairie, which extends 30 miles west of downtown. This prairie acts like a natural sponge for water, but is largely paved over during the rapid growth of the Houston metro area. Even outside of the prairie, urbanization clearly intensified runoff and flash flooding. In fact, planning is not a strong point of development in Houston. The city has no zoning and little regulation of any sort. It’s a pro-business, small-government boom town! You drive around town, and you might see pawn shops next to schools and factories next to churches. So the floodplain is full of housing developments and apartment complexes. To make matters worse, development was permitted inside two large reservoirs, the Barker and Addicks Reservoirs which ironically were originally purchased by the Army Corps of Engineers to protect the downtown from flooding, and many of the families living in the reservoir only found out about it AFTER Harvey. Water levels in the reservoirs were controlled by dams and flood gates, but the Corps had a delicate balancing act. They had to release water slowly down the Buffalo Spillway on the east side to prevent the dam from overtopping, which would have caused a catastrophe, but they could not release so much because that would have flooded downtown. But as it turned out, properties in the reservoir flooded; a gated development called Canyon Gate at Cinco Ranch within the Barker Reservoir with over 700 homes suffered extensive flooding. Those living within the reservoirs may have been more fortunate than those living around it. The Corps released water down the Buffalo Spillway into Buffalo Bayou without warning homeowners and flooded homes in West Houston. There was extensive damage and several fatalities. Needless to say, the Corps has endured severe criticism and lawsuits.

Houston's geographic location on the flat coastal plain of Texas and adjacent to Galveston Bay makes it susceptible to flooding, both from rainfall as in Hurricane Harvey, and from potential storm surge pushing into Galveston Bay.

Credit: Houston, Texas at the Wayback Machine (archived on 10 February 2005)

High and fast water rising in Bayou River with downtown Houston in the background

Credit: Trong Nguyen via Shutterstock

This sequence shows how the flooding occurred around the Barker and Addicks Reservoirs: New York Times: How One Houston Suburb Ended Up in A Reservoir

Long term, there is a discussion about building structures called a berm around what is left of wetlands in the Katy Prairie to provide flood control to development in the western part of Houston. But even then the location of the city and its elevation combined with the sheer amount of concrete and lack of flood control means that storms like Harvey are almost certain to happen again, and it will take a lot more than that to avoid catastrophe in the future. Whole neighborhoods will need to be resettled, and new construction banned in certain locations. But those types of regulations will be a tough political sell in a pro-business town. In 2008, Hurricane Ike prompted a debate that was reinvigorated after Harvey about the need for better coastal protection to prevent storm surges from flooding Houston via the Houston Ship Channel and Galveston Bay, from the Gulf. And the next massive rain soaker of a storm might be on the horizon.

The Bahamas are used to hurricanes. There is no official “hurricane alley” (like tornado alley) but if there were, the Bahamas would be smack in the middle of it. The island nation is generally under a hurricane watch and warning several times a year and has been ravaged by storms in the past. But nothing like Dorian. The storm moved through the Caribbean and took aim on the islands before rapidly strengthening as it approached. Dorian made landfall on September 1, 2019, on Grand Abaco Island with sustained winds of 185 mph and gusts over 220 mph, let me repeat that sustained winds of 185 mph and gusts over 220 mph (!), making it one of the strongest storms on record in the Atlantic and Pacific.

Dorian was an unusual storm in several ways. Remember in the last module we learned that hurricane strength is generally measured by the minimum atmospheric pressure, and Dorian’s pressure was not that low. But, the storm was enormous. Dorian was particularly deadly because the devastating winds were combined with an extremely slow forward motion of about 5 mph so that the storm ravaged the Bahamas for days. Devastating storms like Andrew and Katrina had much faster motion, but the slow speed of Dorian made the damage much, much worse. It’s hard to imagine what it would have been like for all the citizens of the Bahamas to have experienced the impacts of the storm for that long. After pummeling the Abacos, a group of islands in the northeast Bahamas, the storm went back over open water and made landfall without weakening on September 2 on Grand Bahama, the largest Bahama island, where it literally stalled for a day before weakening a little and moving back over open water. The damage to the Bahamas was truly catastrophic, as the pictures show.

The Bahamas had plenty of time to prepare for Dorian. Evacuation orders for low-lying areas were given the day before the storm and residents were urged to seek shelter on higher ground, boats picked people up from small, low-lying islands, and resorts were closed, but even so, many people ignored the warnings. At landfall on the Abacos and again on Grand Bahama, Dorian’s intense winds were accompanied by a massive storm surge of about 6-9 meters (20-25 feet) and heavy rain. In total, about a meter (3 feet) of rain fell over most of the northern Bahamas. Again, imagine experiencing these winds, rains, and storm surge for almost a whole day like folks in the Abacos and Grand Bahama did! It must have been truly terrifying on both sets of islands. There are harrowing tales of people clinging on to trees and other harrowing survival stories, but sadly many were not so fortunate. The official death toll from Dorian is 70, but is almost certainly much, much higher because there were many undocumented citizens living in shantytowns. Initially, there were over 1000 people missing, and now that number is around 300, so the death toll is likely to be 500-600. The true number may never be known.

Watch these short videos that show incredible footage of the peak of the storm and its aftermath!

Video: Hurricane Dorian batters Bahamas with severe flash floods and ferocious wind (1:48)

Video: The town forgotten in the aftermath of Hurricane Dorian (4:33)

On the Abacos, 60 percent of homes were destroyed, in total thousands of homes, including most of the poor shanty town dwellings. The power grid was completely destroyed and the airport flooded. 60% of Grand Bahama island was left underwater, hundreds of homes destroyed and a hospital was badly contaminated by sewage. Dorian will certainly be remembered as one of the most devastating Atlantic storms.

Hurricane Dorian

Moving forward, the lesson from Dorian, like Harvey, is definitely that our warming climate often results in storms that move super slowly. We need to prepare for a Dorian-like storm to hit Miami or New Orleans or under the right circumstances, even Washington DC. Building codes and infrastructure need to be adapted for this eventuality. It’s just a matter of time.

Hurricane Ian: Sept-Oct 2022

Now to Hurricane Ian that hit southwest Florida in September 2022. The storm was notable because of how rapidly it intensified, with wind speeds increasing from 75 mph to 155 mph in just two days. The very large storm came ashore at Cayo Costa island just to the north of Fort Myers on September 28^th, 2022. Sustained wind speeds at landfall were 150 mph, likely with higher gusts. It was the fifth-strongest storm ever to hit the 50 contiguous states.

But the damage in southwest Florida was not just inflicted by the wind. Since the path of the storm closely paralleled the coast as it approached land, and because the highest surge is in the right front quadrant of the storm due to its counter-clockwise circulation, the storm surge over large areas was devastating.

The storm surge was between up to 15 feet above normal sea level along the barrier islands of Captiva, Sanibel, and Fort Myers Beach. This wall of water caused massive devastation in these areas, as observed in the photographs below.

Aerial imagery from NOAA's National Geodetic Survey of damage in the Times Square district of Fort Myers Beach, Fla., after Category 4 Hurricane Ian struck the area.

Credit: NOAA

Aerial photo Fort Myers Beach Hurricane Ian aftermath damage and debris.

Credit: © Felix Mizioznikov Adobe Stock

Hurricane Ian flooded houses in Florida residential area.

Credit: © bilanol / Adobe Stock

Ian moved slowly in the northeast direction across the Florida peninsula, and this slow path caused heavy rainfall over a wide area (see photo above), with precipitation totals of up to 17 inches over a 12-24 hour period. This rainfall caused widespread flooding well inland in places such as Orlando.

One of the main stories of the storm was a prediction. The different forecast models agreed closely as the storm approached southwest Florida, but because the path was so close to parallel to the coast, a small change led to a major difference in the landfall location. Two days out the path was more northerly with the eye forecasted to make landfall near Tampa, but then a day out a minor jog in the forecast to the east shifted the forecasted landfall of the eye well south. This change led to some delays in evacuation in the Fort Myers area.

The storm caused massive damage over a widespread area with catastrophic damage to housing along the coast, especially in Fort Myers, Sanibel Captiva, and Port Charlotte. More than 2.7 million people lost power at the height of the storm, and a large number were without clean water. Overall, the storm led to 136 fatalities in Florida and a total of $50 billion in damage.

Hurricane Helene arose as a depression in the Caribbean. The storm rapidly intensified over the unusually warm Gulf of Mexico as it moved towards the Big Bend region of Florida where it made landfall on the evening of September 26, 2024, as a category 4 hurricane with sustained winds of 140 mph. The hurricane was also very large and had a high storm surge along a long area of the western Florida coastline from about 10 feet in the Big Bend to about 7 feet in the Tampa Bay region, causing extensive flooding along the whole coast.

Since the storm was moving so rapidly it maintained its strength inland and it was still a hurricane when it hit southern Georgia. Wind damage was severe well inland in both states.

Helene was still a tropical storm when it moved across northern Georgia near Atlanta, South Carolina near Greenville, and North Carolina near Asheville. In these regions, some damage was caused by wind, but most of it was done by water. A stalled frontal boundary had dumped up to 9 inches of rain over the mountains of western North Carolina before the storm arrived. The ground was therefore already saturated when the storm arrived, and this led to extensive tree damage from tropical-storm-force winds. Rainfall totals of up to 32 inches in the mountainous terrain caused many landslides and mudslides. The water rushed down the hillslopes causing rivers to rise rapidly, and overflow their banks leading to extensive flash flooding. River levels were at record levels, for example, the French Broad and Swannanoa rivers in Asheville were up to 5 feet above historic levels, breaking a record set in 1916. The results were absolutely catastrophic in Asheville and small mountain towns all over western South Carolina, North Carolina, and Tennessee. Extensive flash flooding swept away single-family homes and mobile homes, and flooded businesses.

Video: Examining Hurricane Helene's shocking impact in North Carolina (7:51)

The most dire result of Helene was loss of life. The storm was the most deadly since Hurricane Katrina with over 280 dead. Over 100 of these deaths occurred in western North Carolina, where many more are still missing at the time of writing. The storm was also the costliest since Katrina with estimates of over $50 billion with billions of dollars of uninsured flood damages.

Video: Surviving after Helene: 'Just living is a challenge' (4:27)

The storm left 4 million people without power, but more damaging was the flood damage, along the Florida coast from the storm surge and in the mountainous regions of the Carolinas and Tennessee from flash flooding. Here the water washed out roads causing severe disruptions to transportation and severed water lines including in larger towns like Asheville. Communication was made even more difficult by the loss of cell phone service as towers were knocked down by wind.

Recovery over the wide area impacted by Helene is still underway with major roles from FEMA and state agencies.

Asheville, NC: One month after Hurricane Helene

In the remainder of this module, we discuss historic extratropical systems. In early 2014 several winters (extratropical) storms developed off the western coast of the U.S. In the case of the storm featured in the video below, the extratropical cyclone had already developed and then merged with a cold front or “atmospheric river” in February 2014. Another event developed a strong rotation later in February and early March. This storm was named Titan. Collectively, these atmospheric river-producing events helped to form large coastal swells and brought much-needed rain to California. The state had been suffering from significant drought conditions for more than 3 years.

Video: Animation of extratropical cyclone merging with atmospheric river off California." (1:06) (Video is not narrated.)

Video: 2/28/14-3/1/14 West Coast Extratropical Cyclone Water Vapor Satellite Loop. (00:58) (Video is not narrated.)

The National Weather Service reported that more rain fell in a few hours than had fallen in eight months as a result of just one of these storms. Due to the relatively steep terrain of the region, and because of the extensive drought, as much needed as the rain was, numerous landslides resulted, and coastal erosion at the base of several sections of the coastal highway was undermined or buried. In some areas, roads were closed and people were evacuated. So, although the storms were not as large in scale as most tropical storms, they definitely impacted coastal regions in many of the same ways.

Below, a home video, taken in 2008 at Marina State Beach, just north of Monterey, California, and south of Salinas River National Wildlife Refuge, shows massive waves some 30’ high. The video illustrates the power of waves as they interact with the shoreline.

Video: Giant Pacific Wave Storm, January 5th, 2008 (1:53) (Video includes people talking, but is not narrated.)

Although the winds don’t appear to be too intense, significant wave run-up is shown, and you can easily see how the swells produce extensive coastal scour and erosion along the shoreline. In the months following, portions of California experienced additional storm activity. Large waves, some in excess of 15 feet, pounded the shoreline up and down the coast. High winds, some gusts as high as 55 mph, were measured, and significant accumulations of snow were dumped at higher elevations, High Surf, Wild Winds Pound Southern California (CBS Los Angeles).

In January 2018 a particularly intense nor’easter impacted the northeastern United States, bringing a freezing storm surge ashore in cities such as Boston. Although this was a rare set of circumstances, storms like this are not uncommon.

The storm originated on January 3rd as an area of low pressure off the coast of the southeastern U.S., which traveled rapidly up the eastern seaboard. The storm explosively deepened during this period, earning the storm its memorable moniker of “Bomb Cyclone.” The storm was also given other unofficial names, such as Winter Storm Grayson, Blizzard of 2018, and Storm Brody.

The term bomb cyclone comes from meteorological terms describing an extreme drop in the central pressure of the storm. Terms including explosive cyclogenesis, weather bomb, meteorological bomb, bomb cyclone, and bombogenesis were used to describe the rapid deepening of the low-pressure area of the extratropical cyclone.

By the morning of January 4, the powerful storm system had deepened by 53 mbar of pressure in 21 hours—one of the fastest rates ever observed in the Western Atlantic (Wikipedia). This drop in pressure was over twice the threshold (24 mbar in 24 hours) for bombogenesis.

In Massachusetts, winds gusted to hurricane-force at 76 miles per hour (122 km/h) on Nantucket Island. At least 17.0 inches (430 mm) of snow fell on Boston. In Boston, a freezing storm tide of 15.16 ft (4.62 m) was recorded during the blizzard which flooded areas of the financial district, including a subway station, setting a new historical record. Significant coastal flooding occurred in Maine and New Hampshire.

Satellite image of the Nor’easter dubbed the Bomb Cyclone of 2018.

Credit: NOAA

In “Beaches are Moving: The Drowning of America’s Shoreline”, coastal geologist and author Orrin Pilkey discusses the four components of shoreline equilibrium – material, energy, shape, and sea level - and how they interact in the event of a storm. He states: “During a storm the strong wind and waves pick up much more sediment than usual, carrying it inland into the dunes or seaward into the waves”…. “Covered by the storm surge, the beach temporarily loses its usual position in the marine environment and becomes an underwater or offshore bar... …the boiling surf keeps the sand particles in suspension, and because the energy of the big waves reaches deeper water, the sand cannot settle until it is either far offshore… or until it is washed up on land to reshape the beach”.

The result, after a storm has passed, is a very different shoreline than before. The energy of water is awesome in its ability to move sediment from one place and deposit it in another. This is often in conflict with the human desire to stabilize and prevent shorelines from moving. But storms and the shoreline naturally interact in a dynamic way. Humans place structures on shorelines, and they get destroyed and rebuilt. But this cannot go on indefinitely.

A point that Dr. Pilkey repeatedly makes is that storms and shorelines are the natural state in a “constant, dynamic balancing of materials, energies and shapes”. When people attempt to change this dynamic equilibrium, a catastrophe happens. This is something to keep in mind as we consider the impacts of the storms we have discussed in this module and as we move forward to explore ways communities deal with these impacts.

Dr. Sean Cornell of Shippensburg University, who does fieldwork on Wallops Island, captured the following images documenting the impacts to the barrier island after Hurricane Irene in 2011. Read through his description and examine the photographs to learn about the local impacts of a hurricane on a barrier island beach. He contrasts Hurricane Irene with Hurricane Sandy, pointing to the difference in angle of approach.

Irene developed as a tropical storm some 300 km off the eastern end of the Lesser Antilles and outside of the Caribbean Sea. It first became a hurricane on August 22, 2011 as it made landfall on Puerto Rico. Despite making landfall, the storm continued to strengthen and eventually became a Category 3 hurricane as it passed through the Bahamas on August 24. The storm then tracked northward and impacted the Outer Banks of North Carolina as a Category 1 storm before emerging once again out into the Atlantic Ocean off the coast of Virginia just south of Virginia Beach on August 28.

As the storm moved northeastward, it ran parallel to the shoreline of the Delmarva Peninsula, where it produced strong winds and waves and high water for the barrier islands and coastal bays located behind the barrier islands, including Wallops Island, home of NASA’s Wallops Island Flight Facility, as well as Chincoteague and Assateague Islands. These barrier islands are nearly continuous along a distance of almost 150 miles of shoreline between the Chesapeake and Delaware Bays. They are interrupted only occasionally by relatively narrow inlets. Nearly 80 miles of this shoreline is relatively undisturbed and undeveloped and is generally allowed to behave naturally and without significant modification by human activity (although see the impact of constructed shorelines at Ocean City, Maryland, and recent coastal engineering projects on Wallops Island to help protect the launch facility and infrastructure). Centered in this region is one of the largest bays on the Delmarva. Chincoteague Bay straddles the Virginia-Maryland border and today has two inlets to the ocean, one between Wallops Island and Assateague Island (i.e., the Chincoteague Inlet), on the south, and one between Assateague and Fenwick Island on the north (i.e., the Ocean City Inlet; see figure below).

Screenshot from the Historical Hurricane Tracks database showing the track of Hurricane Irene as it tracked northeastward along the Delmarva as a Category 1 Hurricane. The locations of Chincoteague Bay, Wallops, Assateague, and Fenwick Islands are noted, as is the position of Ocean City, Maryland.

Credit: NOAA: Historical Hurricane Tracks

For the Eastern Shore of Virginia, and although it was relatively fast-moving, Hurricane Irene was a significant event as the center of the storm passed only about 30 miles offshore. During the onset of the storm, onshore winds and waves piled significant volumes of water along the barrier islands producing storm overwash, eroding shorelines (see images below), and relatively robust storm surge in back bay areas along the mainland (see images below), although nothing is comparable to the levels observed during Katrina on the Gulf Coast, or during Hurricane Sandy in New York. This was, in part, because of the trajectory of the storm, the speed of the storm, the fact that it moved along the continental shelf, and also because the number of inlets was relatively few and narrow. These factors, combined with the robust nature of the barrier island maritime forests and dune systems, helped reduce the total volume of water that could enter the coastal bays. As the storm moved north of the region, offshore winds on the trailing edge of the storm helped to push surge waters back out of the bays and helped produce extensive scouring in the vicinity of the unprotected inlet. This helped form a large ebb-tidal delta that helped fill in much of the navigational channel between Assateague and Wallops. Thus, for this region, Hurricane Irene’s impact was significant but could have been much worse if the storm’s trajectory had been different.

View to the west toward the mainland and salt marsh from the overwash fan on the southernmost tip of Wallops Island at the site of the former inlet separating Wallops from the barrier island to the south. This overwash fan was initiated during Hurricane Irene and was reactivated during Hurricane Sandy as even more wave action pushed the front edge of the island over itself and backward into the salt marsh as part of the process called barrier island rollback. Photo taken 11/2012.

Credit: Nick Matthews

View to the north on the southern tip of Wallops Island on the seaside of the barrier island. Former inter-dune and dune scrub habitats are now exposed in the surf as a result of high water and erosive waves that scoured away the dunes and flattened the beach. Note several tree stumps in the surf. Sediments were moved backward over the island as part of overwash, while some sediment was pulled offshore. As a result of both Hurricane Irene and Sandy, this part of the shoreline retreated landward by more than 4 meters. Photo taken 11/2012.

Credit: Nick Matthews

Photo of the Hurricane Sandy storm scarp produced by beach erosion midway up the newly replenished shoreline at Wallops Island. Finished in the summer of 2012 after Hurricane Irene, an extensive shoreline replenishment project was undertaken to help protect NASA’s launch infrastructure. Although erosion was significant, the amount of damage produced by Sandy, compared to Irene, was significantly less – in part because this new, higher beach protected the shoreline and prevented overwash in this area. Jeep Cherokee for scale. Photo November 2012.

Credit: Nick Matthews

View northward on Wallops showing the southern end of the replenishment area. Prior to shoreline replenishment with offshore sands, NASA had previously utilized geotubes filled with sand to act as wave breaks to help slow erosion and minimize overwash, especially in the vicinity of the UAV runway at the southern end of the island. During Hurricane Irene, these tubes took the brunt of the storm’s fury, and some were completely destroyed. These were buried by the replenishment project, but intensive wave scour re-exhumed portions of the tubes. Subsequent to Hurricane Sandy, dune-building processes have helped to partially rebury the tubes.

Credit: Sean Cornell © Penn State is licensed under CC BY-NC-SA 4.0.

Erosion was also significant during Hurricane Sandy and Katrina on the barrier islands. In this location on the northern end of Wallops Island, Virginia, near the Chincoteague Inlet, an entire beach and dune system was eroded adjacent to the inlet. The amount of erosion was so substantial that waves removed a 10-meter-wide beach and a line of dunes that were built to a height of 8' to 9’ above the normal high tide line. The erosive scour exposed and eroded a line of trees and coastal shrubs seen in this photo. In this case, much of the erosion occurred after the storms moved north as storm surge waters rushed back out of Chincoteague Bay through the inlet to the ocean. The ebbing storm tide produced a strong current that scoured out the margins of the inlet and deposited those sediments in the ebb-tidal delta outside of the inlet. Due to wave action since the storm, many of these sediments are being reworked, and a new beach and dune system is being developed where formerly eroded.

Credit: Sean Cornell © Penn State is licensed under CC BY-NC-SA 4.0.

Hurricane Irene storm deposit on the parking lot of the Assateague National Seashore (September 2011). High waves and storm surge deposited well over 16” of sand (part of the overwash fan) on the beach access parking lot. As a result, hundreds of cubic meters of sand had to be removed by the National Park Service to reopen the parking for Labor Day beachgoers just a few days after Hurricane Irene. Even so, only a few of the 900 parking spaces could be used.

Credit: Sean Cornell © Penn State is licensed under CC BY-NC-SA 4.0.

Shoreline erosion on the mainland side of Chincoteague Bay, Virginia, as a result of Hurricanes Irene and Sandy. Storm surge levels here were approximately 2 meters above mean sea level, and although protected by barrier islands like Assateague and Chincoteague Islands, wind waves were still significant enough to produce erosion around the wooden bulkhead and concrete rip-rap that protected the shoreline in this location. The blue building is owned by Chincoteague Bay Field Station, and was once a NOAA research station. After Hurricane Sandy’s erosion completely exposed the septic tank, the facility is no longer in use and has no electricity or running water. The view is westward toward the little village of Greenbackville, seen in the distance.

Credit: Sean Cornell © Penn State is licensed under CC BY-NC-SA 4.0.

View northeastward onto Chincoteague Bay and toward Assateague Island from Franklin City, Virginia. Previous efforts to help stabilize the shoreline through the use of riprap and old building materials (a common practice used historically) were in vain. Hurricane Sandy, combined with the impacts of Hurricane Irene two years earlier, resulted in erosion and retreat of the shoreline. In some places, as much as 14’ of erosion occurred along this length of shoreline. Where the shoreline was piled up with oyster shells, the erosion rate was significantly lower at around 4’ compared to riprap areas. So, although the erosion still took place, oyster-protected shorelines are usually subject to less erosion.

Credit: Sean Cornell © Penn State is licensed under CC BY-NC-SA 4.0.

A four-foot-high shell bank produced by Hurricane Sandy’s waves as the shells were reworked from the shallow bay. Most of these shells were deposited back in the bay after they were shucked in the shucking houses that once lined the shores of Franklin City, Virginia.

Credit: Sean Cornell © Penn State is licensed under CC BY-NC-SA 4.0.

Hurricane Sandy

In contrast, although Hurricane Sandy was similarly scaled in wind speed and size to Irene, ultimately it was much more impactful further north to New York and New Jersey, primarily because of the storm track it took and the orientation of the shoreline where the storm made landfall. The figure below shows the storm track for Sandy in the fall of 2012. Whereas Irene’s track was parallel to the shore, Sandy’s approach was more perpendicular with landfall toward the northwest. In this way, not only was the brunt of the storm’s energy focused on the shoreline, but the geomorphic configuration of the shoreline and the shallow nature of the inner shelf led to amplification of the storm surge as outlined in the previous module.

Hurricane Sandy’s storm trackway from NOAA’s Historical Storm Track database. As the storm crossed the shelf-slope break, it downgraded from a Category 2 hurricane to a Category 1 hurricane and even degraded to a tropical storm before it came ashore. However, because of its trajectory at nearly a right angle to the shoreline, the full fury of the storm was released on the shoreline of New Jersey and New York. The wedge-shaped shoreline entering the Hudson River Embayment helped to funnel the waters into the embayment, leading to higher and higher storm surge levels.

Credit: NOAA: Historical Hurricane Tracks

A few of our Labs in this course are considered "mini" Labs, meaning the work will not be as involved, and they will not be worth quite as much. However, the work remains just as important.

In this Lab, you will:

• Use Google Maps to examine the impacts of two major storms in two locations.
• Observe and analyze, using street view and historic imagery in Google Maps, the changes to the landscape and communities caused by the hurricanes' surges and winds.
• Compare redevelopment in the two communities and consider the possible factors influencing redevelopment.

Lab Overview

For this short Lab, we tour two locations in the U.S. to view the impacts of two storms: Hurricane Katrina (Aug 29, 2005) in Pass Christian, MS; and Hurricane Sandy (Oct 31, 2012) in Mantoloking, NJ. Both of these storms were unique, and each community had unique characteristics based on the geomorphology of the coastline and the details of the structures built there. While you make your observations, keep these variables in mind. You will assess the damage to the human structures (mostly individual homes) and then use historic imagery and street views to estimate the level of rebuilding that has taken place in the years following the storms. Consider the factors that may influence homeowners' decisions about rebuilding, including the time elapsed and economic factors. Think about how exposed both of the locations are to coastal hazards and the probability of a future coastal disaster impacting this coastline. Your ability to judge details will be limited by the tools you are using, so you will need to estimate and use the online resources provided to help you fill in gaps of knowledge.

Guidance Video

Downloads/Resources

• Module 6 Lab Worksheet
• Pass Christian, MS (Read the section on Hurricane Katrina)
• Mantoloking, NJ (Read the section on Hurricane Sandy)

Instructions

Before you begin the Lab, you will need to download the Module 6 Lab Worksheet. The worksheet contains the steps you need to take to complete the Lab in Google Maps. In addition, it contains prompts for questions that you should take note of (by writing down or typing in) as you work through the Lab. Once you have worked through all of the steps , and answered all of the questions, you will go to the Module 6 Lab Quiz and answer the multiple-choice questions. The questions and answer choices on the lab worksheet will match those in the multiple-choice quiz. Submit the quiz for credit.

Coastal storms ultimately present a great risk to human and natural landscapes. It is probably true that no one will ever die from sea level rise, but millions of people around the world live, work, and play in areas that are prone to the deadly impact of storms. Although modern meteorological equipment has been developed to the point where we now have good success at predicting major storms, evacuation out of harms way is extremely difficult, as we will see in Module 11. And as we will see in Module 7, tsunamis are much greater as the speed at which tsunami waves propagate as well as the complex ways that waves reflect, refract, and interfere with one another as they move around landmasses and across oceanic shelves.

As these phenomena are so incredibly damaging to human societies around the world each year, it is critical that scientists help promote public awareness and facilitate the development of plans to respond, react, and minimize human losses in the event of the inevitable. In Modules 8-13, we will explore, in more detail, the ideas of coastal zone resource management, managing risk, and planning for a more productive, safe, and less impactful future. Given that global warming processes produce more severe storms each year, coupled with the fact that sea level is rising at a more noticeable rate than ever before, many hard decisions have to be made in the future if we are to continue to enjoy the quality of life that comes from living on or near the coastline.

Reminder - Complete all of the Module 6 tasks!

You have reached the end of Module 6! Double-check the Module 6 Roadmap to make sure you have completed all of the activities listed there before you begin Module 7.

• Students will continue to develop the fundamental geospatial skills and concepts needed to assess the coastal processes and hazards discussed in this course.
• Students will develop an understanding of the relationships between the hydrosphere and lithosphere that result in the development of tsunami.
• Students will consider the geology of tsunamis and their impacts on shorelines.
• Students will consider current shoreline processes in the context of coastal hazards and past and present evolution of coastline morphology.

Learning Objectives

By the end of this module, students should be able to:

• describe the geologic phenomena that lead to the occurrence of  tsunamis;
• analyze case studies of how coastal systems are impacted by geologic hazards such as tsunamis;

Module 7 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

Imagine for a moment that you are a dinosaur, 66 million years ago. You live in the lush coastal plains near where the modern city of Galveston, Texas was built in the future. Your life is filled with looking for food, you’re carnivorous, so you spend your days and nights scouting for food: mammals, small reptiles, even fish. You’ve been living in this neck of the woods for decades and nothing much perturbs you. You’re in charge of your destiny.

Then everything changed. It all happened very fast, you see a bright light in the sky to the east, a searing flash, and next, a boom that is the loudest sound you’d ever heard, so loud it deafens you (if it mattered, but sadly it doesn’t). The ground shakes violently: earthquakes almost never occur in these parts, and this is a magnitude 13, likely the largest quake Earth has ever felt! Your giant 50-foot-long frame is thrown to the ground, and you lie there stunned. Next, you are hit by searing heat, a giant fireball approaches from the ocean, skirting the water, wave after wave of heat burns your skin, and you roar in agony. But then you see it -- a giant wave coming also from the same direction -- you have seen storms before, even some hurricanes, but nothing like this. It’s a wall of water, some 90 meters high coming at you, there is nowhere to go, you begin to run towards the land, but it’s no good. After millions of years of dominance, it’s all over.

Well, of course, this is fiction, most dinosaurs were not drowned. Most likely died slowly because climate change that was a result of the impact hitting very volatile sedimentary rocks emitted a lot of climatically active gasses and soot, which cooled the planet by 25 degrees C for decades. Vegetation stopped growing, herbivores died off and ultimately so did you, the carnivorous dinosaurs. You didn’t drown, you slowly starved.

The tsunami part is true. The impact did generate a massive tsunami, and it was one of the largest waves Earth ever experienced. The asteroid that hit the Earth 66 million years ago was 8-10 km across and traveled from the northeast at a velocity of 20 kilometers per second which is 45,000 miles per hour, (!) causing the flash the dinosaurs observed. The collision was so violent it released an estimated 100 teratons of TNT, the equivalent of a billion nuclear bombs (the deafening sound and the earthquake). The collision released a blast wave and a fireball that incinerated vegetation along the coastlines of the Gulf of Mexico (the burning sensation). The colossal Chicxulub crater formed in a matter of minutes, in one of the most dramatic movements the Earth has ever experienced, rocks from depths of more than 20 km were excavated to the surface as a giant ring of mountains. The crater is what is known as multi-ringed, which means it is made of concentric faults that get progressively deeper towards the center.

The crater has a diameter of 200 km and a depth of about 1 km, a giant hole in the ground that slowly filled with seawater over a period of hours. This wasn’t a slow seeping in of water, it was a massive surge, huge waves of water entering the crater. The crater had numerous connections to the surrounding ocean for this water to surge in, and once the crater was filled, giant waves of water exited as a massive tsunami. There were several phases in tsunami development.

When the water rushes back in it forms a central plume (a giant splash) that collapses outwards causing tsunami, this is known as a rim wave tsunami, the first tsunami to form. This wave would travel outside the crater and be the first tsunami to hit the Texas coast. However, it was not the last. Imagine dropping a huge boulder into a bathtub filled with water. The rim wave tsunami forms from the initial big splash (the plume) when the boulder displaces the water. This wave will travel out to the edges of the bathtub and reflect off of it. That is what happened in the Chicxulub crater, the rim wave tsunami hit the shores of the Gulf of Mexico and caused numerous reflected tsunami. But that wasn’t the end. The crater was unstable, with massive piles of rubble all over the place, and giant landslides were occurring everywhere. In addition, the tsunami were so big that they themselves triggered landslides. As we will learn in this module, landslides also trigger tsunami. So there was total chaos that lasted for days, multiple tsunami of varying size going in and out of the crater. And once the tsunami waned and energy began to subside, seiche waves formed, these were waves that did not exit the crater. It took months for the energy to totally diminish. Watch these simulations here:

Video: Chicxulub Tsunami (4:07) (No audio.)

We can study cores of rock drilled in the crater to learn about the tsunami. Tsunami deposits are also found all over the margin of the Gulf of Mexico in Texas, Alabama, Mississippi, and northern Mexico. Giant boulders deposited by landslides are found in Cuba. Seiche waves likely made it all the way up to North Dakota! The crater has been drilled, including by a rig in 2016, and cores tell us about the timing and the physics of the tsunami. Also, geologists have worked on rocks around the Gulf of Mexico and the Caribbean that provide information about the height of the wave and how far it extended inland. Some of these rocks are shown below.

So it was a really rough day for you the dinosaur, it was the end of an era, the Mesozoic, when you ruled, you may have been swept out to sea by that first rim wave tsunami, but in all likelihood, your relatives suffered a far slower demise.

Possibly the largest tsunamis ever experienced were triggered by massive landslides off the flanks of Hawaiian volcanoes. And these unstable areas will fail again in the future and trigger a massive tsunami that may devastate coastlines around the Pacific Ocean. It’s not a matter of if, it’s a matter of when.

Hawaiian volcanoes are some of the fastest-growing landforms in the world. The Pacific Plate is moving to the northwest over a massive plume of heat known as a “hot spot”. The plate is moving to the northwest at a rate of 10 cm per year and there is a clear age progression of volcanoes from older on Kauai the northwesternmost island to younger on the southeast flank of the Big Island, Hawaii. In fact, the active youngest flanks are those that have the potential to fail in the future, as we will see.

The evidence for landslides is super clear. Images made with sonar show pockmarked areas of seafloor littered with massive blocks of displaced material off the flanks of islands that show evidence for past failure.

The Nu’uanu slide lies off the northeast coast of the island of Oahu and is one of the largest landslides on Earth. The slide is 235 km wide and 35 km long and occurred 1 to 1.5 million years ago when nearly half of the Ko’olau volcano collapsed. One of the largest blocks in the slide is called the Tuscaloosa seamount, which is 30 km long by 17 km wide and 2 km high! The remaining part of the caldera shows a steep fault escarpment where the failure occurred. The Wailua slide off the north coast of Molokai lies close to the Nu’uanu slide and occurred 1.4 million years ago when the East Molokai volcano collapsed. The slide is 195 km long and 40 wide. The volume of material generated by these two slides must have caused massive tsunamis, or megatsunami, which models suggest were up to 100 m high on the coasts of the Hawaiian islands! One possible piece of evidence for tsunami is found on the island of Lanai, where blocks of coral are found 35 meters above sea level. Such corals could not have grown at these elevations and must have been delivered by tsunami. In all likelihood, tsunami generated by these events hit the west coast of the US and Canada, but there is no known record in these locations.

Hawaiian volcanoes grow, with lavas spreading out from the crater at rapid rates. GPS data show extremely fast motions of 10cm/year along the southeast flank of the Big Island of Hawaii, the youngest Hawaiian island. All eyes are on this margin where recent collapse formed the Hilina slide and current gradual movement is forming the Hilina slump. This coast is also where future flank collapse looks likely, and the arcuate cliffs of the Hilina Pali look like possible pre-collapse features.

This rapid motion has caused visible features in the Hawaiian landscape. The so-called Great Crack on the southwest rift zone of Kilauea is 6 miles long, 60 feet wide and 60 feet deep in places and is and highly visible in Google Earth. The crack is in no immediate danger of failing, but is a reminder that the rapidly accreting Hawaiian islands pose a unique tsunami hazard in the Pacific Ocean.

The island of Santorini (also known as Thera) is widely considered the most dramatic Greek island and one of the most beautiful places in the world. White homes are plastered on the side of rugged hills and travel is by donkey. Once the island was a massive volcano that erupted numerous times, but with one final and fatal eruption about 1600BC (the exact number is argued). The steep hillsides on the island were produced during this giant eruption, with massive quantities of lava and ash erupting from a small cone in the middle of what is left of the island. Now the island is like a cut-off horse-shoe with the ocean on all sides and the cone in the middle.

There were several phases in the eruption, including both lava fountains and the generation of deadly and hot mixtures of ash and gas. These mixtures can flow at speeds of 300 kilometers per hour and are often sprayed up into the air as massive columns many kilometers high that can collapse. The collapse of these columns into the ocean is thought to be a process that can generate a massive tsunami, as we will see in the 1883 eruption of Krakatoa, and it is thought that several phases of the Santorini eruption did this. The volcano had originally been a typical mountain-like structure with steep sides. In the later stages of its history, as the magma chamber emptied out, the mountain basically collapsed into a wide crater known as a caldera. The final two stages of the 1600 BC eruption led to the collapse of the caldera, and it's filling up with seawater. The final dramatic collapse which formed the horseshoe-shaped ring of the modern Santorini also generated the well-known megatsunami.

The phases of the eruption are known from well-preserved, layered records of the eruption that are up to 7 meters (23 feet) thick on Santorini but also found at archaeological sites including the well-known ruins in Crete. The eruption was certainly disastrous for the late Minoan civilization on Santorini, but what about elsewhere? The one-thriving Minoan civilization on Crete collapsed around this time and there have been numerous theories about how this related to the eruption. Was it the ash that blanketed the island? A giant earthquake associated with the eruption? Or the massive tsunami?

The famous North entrance of the Knossos palace on Crete, once a thriving hub of the Minoan civilization

Credit: Scorpp via Shutterstock

The famous dolphin fresco from the Knossos palace

Credit: Andy.M via Shutterstock

The tsunami deposit is found all over the eastern Mediterranean, including in deep-sea cores and in northern Crete, western Turkey, and as far away as Israel. There is much debate about its size and impact, however. Simulations have a tough time generating a large tsunami. However, a discovery about ten years ago in Crete provides some clues. At the Palikastro archeological site on the northeast tip of the island, a fascinating layer contained the Santorini ash, broken up building stones, marine fossil shells including those of beach and open ocean organisms, pieces of ceramics and even bones. The distribution of this layer on the rugged shore and in the areas above it suggests that the maximum wave height was 35 meters high! However, the impact of that wave on the Minoans is still debated and unlikely to have been the sole cause of the end of this civilization.

One of the first disaster movies ever made was about the giant tsunami of 1883 that was triggered during a massive eruption of the giant volcano, Krakatoa, about 20 miles (32 kilometers) from the islands of Java and Sumatra. The movie included a group of thieves and a group of good guys. They are on Java, getting ready to set sail to look for lost treasure. They see the volcanic eruption in the distance, feel the ground shake and the ocean recede, and know that a tsunami is coming. They have a decision to make: stay on land and get to high ground, or escape on a boat and ride the wave out at sea. So the good guys get in the boat, and the bad guys run for higher ground. The boat gets out to sea, where it is rocked by giant waves, but barely survives. The bad guys climb trees and are swept away by the waves. Justice is served! The movie ends.

Poster of the infamous disaster movie

Copyright © 1969 Cinerama Releasing Corporation. All rights reserved

Think about how inaccurate this storyline is for a minute. While the characters would have felt the earthquakes, the tsunami would have arrived in about THREE minutes (at 800 km/hour). So there would have been almost no time to stand around and make that fateful decision, and certainly not enough time to steer the ship out into open waters. And finally, the movie is infamous because Krakatoa is actually WEST of Java!

Krakatoa is a massive stratovolcano that lies between the islands of Java and Sumatra in the Sunda Strait. The volcano is still active today (it erupted in 2020) and rises out of the ocean with numerous small island cones. The 1883 eruption was by far the largest in its history and basically blew up the majority of the volcano. Eruptions began on May 20 of that year as documented by historic records, and these led up to the massive eruption that began on August 25 and lasted for two days. That eruption is what is known as a culminating eruption, where much of the volcano literally blows up, and, in the case of Krakatoa, all that was left was one flank of the volcano and a couple of small cones in its center. The sheer power of the eruption was caused by what is known as phreatic activity. Because the volcano was right next to the ocean, seawater seeped into the plumbing system, and, when heated, became steam.

Evolution of Krakatoa through time, showing how the volcano almost disappeared in 1883

Credit: Krakatoa_evolution_map-en.gif by Sémhur derivative work: Morn via Wikimedia Commons CC BY-SA 3.0

The eruption was so powerful that it was heard in Perth in Australia, more than 3000 km away, and may have been the loudest sound heard in historic times. Ash from the eruption stayed elevated for months and caused spectacular sunsets around the world in places as far away as New York and Norway. The famous painting The Scream by Edvard Munch is thought to depict one of these dramatic sunsets. The global temperature dropped by 0.4 deg C in the year after the eruption, as a direct result of the emission of sulfur dioxide that blocked out solar radiation. Record rainfall occurred in California.

The blood-red sky shown in Edvard Munch's famous 1893 painting The Scream depicts the color of the sky over Norway after the eruption.

Credit: The Scream by Edvard Munch via Wikimedia Commons (Public Domain)

When Krakatoa erupted, it generated a massive column of ash, pumice, and gas that extended up to 27 km above the volcano. The collapse of these columns displaced several cubic kilometers of seawater, and this is thought to have been the trigger for the massive tsunami that caused so much destruction. Waves up to 46 meters high (120 feet) crashed onto coastal villages in Java and Sumatra and killed up to 36,000 people. The coastal areas are very flat, there was little warning (sorry, Hollywood!), and nowhere to escape.

The collapse of the column spread a massive cloud of hot ash and poisonous gas called a pyroclastic cloud or surge that basically burned and asphyxiated anyone in its path and caused at least 4000 fatalities on the islands of Sumatra and Selebesi. Large pieces of pumice landed around the region. There are reports of corpses washing up on volcanic pumice in Africa in the months after the eruption.

Sadly, the 1883 eruption was not the last time an eruption of Krakatoa caused massive fatalities. The Anak Krakatoa volcano violently erupted in December 2018 and triggered a tsunami that led to over 400 deaths and over 800 injuries on Java and Sumatra.

Tsunami victims collect items from a damaged house in the Carita district, Banten province, Indonesia, on December 28, 2018

Credit: Fajrul Islam via Shutterstock

Video: Krakatoa volcano explodes: spectacular huge eruption two months before 2018 tsunami (0:54) (Video is not narrated.)

Krakatoa East of Java was made in 1969, the first of many super wildly inaccurate disaster movies. In “Earthquake,” giant cracks opened in the ground in Los Angeles and swallowed people whole (including the bad guys!). Still worse, in “Volcano”, an eruption takes place in Los Angeles (there are no volcanoes even close to the city!). “Dante’s Peak” did a little bit better, at least it took place in a region where there are volcanoes, but imagine making a truck to be lava resistant so that the family pet can make his last-minute escape! And this is without the wildly inaccurate storm movies!

The 1883 Eruption of Krakatoa shows the devastation that a volcanic tsunami can cause. It was not nearly the largest eruption in the region, however. The eruption of Toba 75,000 years ago was many orders of magnitude more powerful and is thought to have caused more than 3 degrees of global cooling that lasted a number of years. Thick ash from this eruption is found all over the Indian Ocean, and a thin layer is found in Greenland ice cores. The Toba eruption must have generated a truly monstrous tsunami!

The Canary Islands are a group of seven volcanic islands that lie 100 kilometers off the coast of Africa. These islands grew over a hotspot as in the Hawaiian islands and all but one has active volcanoes. The coastlines of the Canaries are characterized by massive, steep cliffs and there has long been speculation that these features formed by dramatic collapse. What makes this possibility super significant is the fact that this process could trigger massive tsunamis that could hit the coasts of Europe, the eastern seaboard of the US, and Antarctica. In fact, speculation is that giant blocks of limestone that weigh hundreds of tons meters above sea level in the Bahamas were delivered there by a megatsunami and the Canary Island landslides are a possible culprit. And more locally, tsunami deposits found in the Canary island suggest waves in the past over 150 meters high!

Cumbre Vieja is the main volcano on the island of La Palma and has erupted recently, causing large cracks to grow involving the significant motion of the western volcano flank. This has caused speculation that this flank could collapse. The flank has a volume of 1.5 trillion metric tons and models suggest that if it were to collapse it would generate a tsunami 1000 m high that would be 50 m when it arrived in Europe and along the eastern coast of the US. Because this scenario would be devastating to cities including New York, Boston, and Miami as well as coastal real estate in New Jersey, North and South Carolina, and Florida, it has been rigorously investigated by scientists.

Video: Megatsunami Scenario - La Palma Landslide (4:48)

The hypothesis that Canary Island collapse generates megatsunami is not universally accepted. This skepticism arises from the fact that island collapse may not have been catastrophic, instead, occurring slowly in numerous discrete small events rather than a single giant collapse. Such a slow collapse would not generate a large tsunami. So what about the large Bahamian blocks? An alternative possibility is they were delivered there by a hurricane during a time 125,000 years ago when sea level was higher than it is today.

In summary, it does not appear that a devastating megatsunami generated in the Canary Islands is imminent. There is potential for collapse of the volcanic flanks on the islands but these events will likely be less dramatic than once feared and with waves only devastating on a local scale.

In the discussion below, we will explore two case studies. The first is the Sumatran tsunami from 2004, which we will use to explore the geologic origin of tsunamis, how tsunamis are generated within the water column, how they travel, and the impacts that they have on shorelines. The second case study will spend time exploring the most recent large-scale tsunami and associated impacts in Japan. Please click the first case study below or in the menu to get started.

The Boxing Day 2004 Earthquake: A Holiday's Worst Nightmare

It is an idyllic morning to be at the beach, the day after Christmas 2004, bright sunshine and balmy temperatures greet vacationers on the tropical island of Phuket in Thailand. Kids run in the waves and build sandcastles, and sunbathers relax. The ocean slowly recedes, exposing rocks below the low tide line and much further, and stranding fish. People venture way out to see this surprising phenomenon. The Earthquake off Sumatra occurred at about 7 AM local time, it was about 500 km away, and no one here felt shaking.

A few people had heard about it on TV, but no one put two and two together---the ocean often recedes as a tsunami approaches. A wave appears on the distant horizon, a bright white band on the ocean surface moving slowly toward the land. People stare at it, puzzled. Gradually, it dawns on some that the wave is dangerous, but others don’t realize it until it’s too late, especially those who had wandered out. The wave is moving really fast. The peaceful beach scene gradually becomes gripped by panic. People flee as fast as they can and run for higher ground. The wave quickly covers the beach and heads for the luxury beachfront hotels. Pools are covered, and beach chairs move around like tinker toys. People cling to trees or desperately clamber up to higher floors to escape the wave. Others have already rushed to higher ground inland. The scene at Phuket is similar to many other resorts in Thailand and Malaysia. The wave reached up to 6 meters or 20 feet high here. Up to 300 people lost their lives in Phuket, and many more were injured. But while there were places to escape to inland if you were fast enough, that was not an option in the Phi Phi islands, also in Thailand. The lovely beach there is backed by dramatic, steep limestone cliffs, and there are few hotels, just low-lying beach cottages. The tsunami was also up to 6 meters at Phi Phi, and as many as 4000 people died, though the total could be far higher.

The date couldn’t be worse for such an event to occur; with thousands of people on holiday in the region and with very few people working in government offices, it was a recipe for disaster. Tourists from all over the world were vacationing in seaside resorts in Thailand, Indonesia, India, and elsewhere. Unplugged as they were, it was next to impossible to inform them or the residents of the region of the impending hazard.

Banda Aceh, the capital of the Aceh province of Sumatra, was much closer to the earthquake epicenter, and people felt the shaking. However, they had very little time to do anything, and there were no warnings about what was to come. And to be effective, a warning would have had to have gone out immediately. About 20 minutes later, three successive waves arrived; the first wave was smaller, but the next two were so large that they reached as far as 4 km (2.5 miles) inland. The water was up to 12 m (40 feet) high in the city, and the impact was truly devastating. Houses were totally destroyed, and wreckage, cars, and anything else were carried inland on this massive, muddy wall of water and debris. Outside of the city, the wave was even higher, up to 30 meters (100 feet) high on the west coast of Aceh province, where it traveled 3 miles inland. The highest measured wave reached 51 meters (167 feet) on a hillside near Banda Aceh. A total of 167,000 people are known to have died in Banda Aceh, and many more were missing. The video shows footage of the devastating tsunami in Banda Aceh, followed by Phuket.

Video: Boxing Day Tsunami 2004 Thailand (9:16) (This video has on-screen text, but is not narrated.)

Now let’s take a step back and understand the megathrust earthquake that generated the tsunami. Remember a megathrust earthquake is one that occurs in a subduction zone where one plate is descending under another. These types of motions tend to cause a lot of strain to build up and thus then produce massive amounts of energy when it is released, the fault ruptures, and the crust moves or slips. The slip can encompass the movement of massive areas and involve different motions on either side of the plate boundary. In terms of tsunami genesis, as we have learned, the critical part of the motion is that the megathrust often causes rapid upward motion of the crust (and downward motion in some areas). And, of course, these fault zones are almost all under the ocean.

The 26 December 2004 Sumatra Andaman Earthquake took place when the Indian Plate is subducting beneath the Sunda Plate, actually, a small microplate belonging to it, the Burma microplate.

The earthquake was the third-largest quake ever measured with a magnitude of about 9.1. Two other notable elements of the quake were that it involved eight to ten minutes of shaking, which is a very long time compared to most quakes. The rupture took place in several stages with a total of 15 meters or 50 feet of movement over a length of 1500 km (900 miles), and the area of slip was truly massive, about the size of California (as seen in the image below).

The rupture actually involved a complex set of faults with some very rapid upward motion, which triggered the tsunami. The initial rupture occurred above the earthquake epicenter and then propagated to the north at a speed of 2km/sec or 1.2 m/sec (see image below). The fault that moved was up to 50 km (30 miles) deep, and the total amount of motion at the epicenter was about 20 meters or 65 feet. The megathrust motion caused the Burma microplate to move upward rapidly.

The upward motion was enough to make new islands. The animation below shows how the crust moved upwards in propagation from the south toward the north. It is very easy to see how this motion generated a tsunami. The second animation shows how tsunami waves spread out from the area of upward motion. You can see that the waves that hit Banda Aceh in the south of the map came from a different part of the plate boundary from those that hit Thailand in the north.

The earthquake was so large and the plate motion so significant that the 2004 Sumatra-Andaman earthquake is thought to have triggered other earthquakes in a process known as dynamic including the deadly 2008 Sichuan earthquake in China that killed 69,000 people.

Learning Check Point

After examining the diagrams and maps on the USGS’s Pacific Coastal and Marine Science Center website and watching the animation video of the modeled tsunami waves that were generated by the earthquake. Take some time to think about what you just learned, then consider how you would answer the questions on the cards below. Click "Turn" to see the correct answer on the reverse side of each card.

Just a few years after the 2004 event, another large-scale tsunami hit one of the most prepared and most technologically advanced countries in the world. The event occurred on March 11, 2011, when a massive 9.0 magnitude earthquake occurred off the eastern coast of Japan, one of the five largest quakes of the modern era. The quake occurred off the coast of the Tohoku region of Japan; hence it is called the Tohoku earthquake and tsunami.

The geologic context was nearly identical to the 2004 event in Sumatra. An eastward directed mega-thrust earthquake disturbed the seafloor. Even though the area disturbed was smaller than offshore Sumatra, it was still massive and had a similar energy release, and it generated a substantial tsunami that raced across the Pacific Ocean, and, most ominously, towards Japan. The Pacific plate to the east of Japan is moving westward under the North American Plate. Seismic data show that parts of the Pacific Plate moved westward by up to 40 m (130 feet) during the quake! The map below shows the amount of movement, known as slip, on the landward North American Plate, and you can see from the darkest red area, a huge region also moved 40 m (130 feet) in a matter of 2 or 3 minutes! The earthquake moved the island of Honshu 2.5 m (8 ft) to the east and shifted the whole Earth off its rotational axis by 10 to 25 cm! Parts of the Japan coast dropped by 0.6 m (2 ft), making the tsunami more devastating, and parts of the seafloor rose by 7 meters (23 feet)! The earthquake rupture mechanics are well known, with an initial speed of 1.5 km (about a mile) per second. So from those last two numbers, 7-meter motion and 1.5 km/sec, you can see how the quake generated a tsunami! The depth of the major quake was 30 km, but numerous aftershocks for various magnitudes occurred for two weeks after as you can see from the red dots in the map below.

The quake generated a tsunami wave that came ashore on the Japanese coastline less than an hour after the earthquake. The tsunami wave was detected about 25 minutes after the earthquake by a DART buoy. This model produced by NOAA’s Tsunami Research Center (NCTR) in Seattle, Washington shows the predicted path of the March 11, 2011, Honshu tsunami as it propagated around the Pacific.

The two videos below show terrifying up-close footage of the earthquake and tsunami:

Video: 2011/03/11 Great East Japan Earthquake, Tsunami (7:00) (Video is not narrated.)

Video: Dramatic unseen footage of Japanese tsunami (3:24)

Video: March 11, 2011, Honshu, Japan Tsunami Propagation (1:10) (Vidoe is not narrated.)

Check out NCTR Tohoku (East Coast of Honshu) Tsunami, March 11, 2011. Also on the site is a maximum wave amplitude model produced by the MOST tsunami model and a new narrated animation of the tsunami propagation and maximum amplitude model. Even more exciting is the fact that NCTR now has a Google Earth interface that provides users with access to datasets (tide data, DART buoy data, etc.) that record water levels in shallow water regions as well as out at sea in deep water where they present water column height (in meters above the seafloor). More on this later.

In any regard, as the length of the fault rupture was relatively small compared to the 2004 Sumatran event, wave propagation was more spherical, and although tsunami beaming occurred, seamounts and other submerged obstructions in the direction of the most prominent beaming direction (i.e., toward the southeast) helped to bend and refract the direct wave so that it lost some of its amplitude as it traveled toward Hawaii and South America. Data measured by tsunami buoys showed that the initial wave close to the fault observed a nearly 2m amplitude wave. As the wave moved toward the southeast, the amplitude subsided to less than a meter, likely as a result of interference as mentioned here. However, the beaming that focused toward the northwest meant that the full force of the direct wave was squarely on the island of Honshu. Given the orientation of the shoreline with numerous river valleys opening to the east and southeast (see below), the tsunami waves were funneled full force into shallow waters and up the progressively narrower valleys located up and down the coast of Honshu.

So, although much had been learned from the 2004 event, and although the tsunami warning system is more advanced and sophisticated and although it had helped to detect and measure the tsunami wave, unfortunately, the tsunami produced an incredible trail of destruction across northern Japan. As discussed, the Tohoku earthquake resulted in uplift and subsidence of portions of the seafloor in northern Japan and some of the shorelines subsided by 0.6 meters. The tsunami was a combination of 10-meter waves that led to wave run-up heights of almost 40 meters (over 120 feet) in some areas, and traveled inland through low-lying river systems at least 10 kilometers and caused over 500 square kilometers to be flooded.

Most coastal defenses were insufficient in preventing the destruction, as tsunami seawalls were overtopped or destroyed in many communities. Perhaps the tsunami warning system didn’t function as intended and notice didn’t reach the population. Perhaps the wave was generated so close to shore there was so little time. Perhaps a false sense of security was afforded by the coastal infrastructure built to protect the shoreline. Nevertheless, as a result of the 2011 tsunami, more than 15,000 people died when entire communities were wiped from their seaside locations. The vast majority died as a result of drowning. When you search the Internet, you will easily find tons of videos showing people desperately trying to move to high ground as the wall of water surges inland behind them. There are even videos of residents on the tops of taller buildings who thought they were safe, but who were also washed away. In addition to these frightening occurrences, the tsunami triggered a series of events that led to the failure of the Fukushima Daiichi nuclear power plant. When the plant failed, the nuclear meltdown led to the release of radioactive materials that ended up in the atmosphere and the Pacific Ocean. In addition to radioactive materials, the Japanese government suggested that more than five million tons of debris were washed out to sea as the surge waters retreated to the sea. As a result of these and other damages, estimates for damage topped 300 billion dollars in Japan alone, but real costs were far greater and continue to mount as a result of clean-up efforts and as a result of the environmental impact on fisheries and agricultural areas that supply food to the population. Tohoku's Six Minute Nightmare provides photos and video from the event that are incredible to look at and fundamentally demonstrate how destructive these events can be.

Further away, there were also some noticeable impacts. An entire colony of nesting seabirds (in excess of 110,000 birds) was washed away on Midway Atoll. Relatively minor impacts were felt in Hawaii and along the West Coast of the U.S. The tsunami wave continued to travel over 17,000 km and came ashore in Chile where it produced a modest wave of about 2 meters, luckily occurring near low tide so the impact was minimal. Luckily, the tsunami warning systems went into place and no one was killed as a result. In Antarctica, the tsunami waves broke a number of icebergs off the Sulzberger Ice Shelf. The same event was even linked to a number of impacts in the fjords of Norway where waves nearly 2 meters in height sloshed back and forth around the fjords located along the Norwegian Sea in the northeastern part of the Atlantic Ocean. These waves, termed seiches, were terrifying for local residents and produced some minor damage, but no casualties. Other occurrences have been tentatively linked to either the earthquake or the tsunami wave.

The 1700 tsunami that impacted the Puget sound region was triggered by a megathrust earthquake off the coast of northern California, Oregon, Washington, and British Columbia on the so-called Cascadia margin. The event happened on the evening of January 26th as documented in Japanese historic records. In Japan, the event was called an “orphan” tsunami because the earthquake was so far away it was not felt. The other significant piece of evidence for the tsunami comes from dead trees in so-called “ghost” forests in Oregon and Washington that can be dated using carbon 14 and tree ring studies. These trees in lush coastal forests are thought to have been instantly killed by the saltwater when they were flooded initially by up to 12 m (36 feet) of land subsidence associated with the megathrust earthquake and then by the tsunami. The photo below shows the Neskowin Ghost Forest on the Oregon coast. We see many tree stumps sticking up above the sand at low tide. These trees were killed by a tsunami in 1700 when the elevation of the land fell, and they were completely inundated and then buried by sand. Large storms eroded the sand from the trees and exposed them. They remain as evidence of the huge tsunami more than 300 years ago.

Oral accounts from indigenous Native American and First Nation tribes living on the coast of Vancouver Island in Canada that have been passed down from generation to generation tell of an earthquake and tsunami on a winter’s evening. The accounts describe that all the low-lying settlements were wiped out and the only survivors were those people who lived 75 feet above the waterline. So the tsunami must have been massive!

Subsidence and tsunami records suggest that the earthquake was in the range of a magnitude 8.7-9.2 on the Richter scale. So what is a megathrust earthquake? It’s a very powerful quake usually close to or greater than a magnitude 9. These quakes occur at subduction zones where one plate is thrust under the other. When this happens the overriding plate moves upwards rapidly and this is what typically generates the tsunami. What is incredible about these events is the motion covers such massive areas. In the 2004 Indian Ocean event, an area 180 km wide and 1000 km long moved up by 30 meters! In the 2011 Tohoku event, an area 200 km long by 500 km wide moved up by 20 meters!

Back to Cascadia. The whole margin from Northern California to British Columbia lies about 200 km from the plate boundary where the Juan da Fuca Plate is sliding beneath the North American Plate. Paleoseismology, the exploration of evidence of ancient quakes from rocks, has become a cottage industry here and suggests that a major (i.e. megathrust) quake occurs every 500 years on average. So it’s been 300 years since the 1700 event and thus getting close to the time for another major event. The probability of such a massive quake in the next 50 years is about 12 percent, about 1 in 8, which is not insignificant.

This is the scenario that could play out on the Cascadia margin. A magnitude 9 earthquake rocks the plate boundary leading to a 1000 km long rupture including significant vertical displacement. This generates a tsunami that travels at 800 km/hour. Folks on the coast will feel the earthquake waves first with a magnitude between 7 and 8. This severe shaking will crumble older buildings with poor construction, collapse bridges, and cause landslides and soil liquefaction (when waterlogged soils behave like Jello---see images below from Alaska of the potential damage from liquefaction), stranding communities, and hampering relief. But everyone on the coast will know that the worst is yet to come and that they will need to evacuate as soon as the land stops shaking. The deformation that occurs along the plate boundary could cause land at the coast to sink by up to 6 feet (2m) making the coastal zone much more susceptible to flooding. The first tsunami wave will reach the coast from Victoria Island in Canada to Northern California in 15-20 minutes giving folks very little time to escape to higher ground. The waves could be 30-40 feet (9-12 m) in height when they hit the coast but some models suggest they could reach 100 feet (30 m), and in many parts of the coast they would flood up to 10 miles (16 km) inland. Some parts of the coast are a lot more vulnerable to tsunami inundation than others, and citizens in these locations will have to move to higher ground extremely rapidly once the earthquake waves subside. The waves will keep coming and since they have such long wavelengths it will take hours for the water to subside.

Earthquake Damages

Video: The Next Cascadia Earthquake: Worst-Case Scenario (8:07)

The following video describes the likely impact of a megathrust Cascadia earthquake.

Such a disaster will happen along the Cascadia margin at some time in the future. The damage and impact will depend on the mechanics and location of the quake, the amount of coastal subsidence, the amount of damage by the earthquake, and the height of the tsunami waves. The good news is that public awareness is significant. There has been a lot of media attention, and local governments have been investing heavily in public safety projects.

Video: NOAA Tsunami Forecasting (2:33)

Today, in partnership with the USGS and NOAA, the US Tsunami Warning Center operates from Hawaii. The warning center was first created after WWII as a result of the 1946 Aleutian Island tsunami that originated between Alaska and Siberia. The tsunami produced incredibly destructive waves that traveled hundreds of miles to the south and resulted in the severe inundation of Hilo Bay, Hawaii and led to numerous deaths. Formerly initiated in 1949, the center expanded in the aftermath of the 1960 Chilean earthquake that not only destroyed many communities along the coast of Chile but also led to more destruction in Hawaii and even in Japan on the opposite side of the Pacific Ocean. With such severe long-distance impacts, it was clear that individual nations needed to collaborate in order to effectively save lives. As a result, efforts were initiated to coordinate monitoring around the Pacific, but even in 2004, the effectiveness of the center was limited as demonstrated by the 2004 Sumatran Tsunami that impacted much of the Indian Ocean. Although the earthquake and tsunami were detected from the Pacific, little could be done to monitor its progression in the Indian Ocean, and efforts were more or less futile in terms of issuing effective warnings to residents living around the Indian Ocean basin. As a result of that event, the center now coordinates with other tsunami warning centers in the U.S.and with the United Nations and similar agencies in several other countries including Japan, Australia, and others. These centers not only detect earthquake activity but also track the development and movement of tsunami waves as they travel across the world’s oceans. The main missions of these centers are to monitor and issue warnings, advisories, and watches to help reduce the loss of life associated with these events around the world.

The US Tsunami Warning Center is a great resource that provides details about specific events around the globe that are being monitored for tsunami generation. Australia and a few other countries maintain similar websites. It is worth spending a little bit of time exploring the types of tools and data that these agencies are collecting and monitoring to help keep the public as safe as possible from these types of catastrophes. It is, however, up to individuals and communities to be educated about tsunami risks and hazards and to act on the information provided in order to save lives. Individual communities are ultimately responsible for developing evacuation plans and limiting shoreline development, in especially susceptible areas. These topics will be explored in greater detail in later modules.

It’s clear that tsunamis pose an incredible threat to coastlines and societies around the world; but exactly what are tsunamis, how are they formed, and how do they interact with coastlines around the world? In order to answer these questions, we will explore two case studies. The first is the Sumatran Tsunami that occurred in December 2004, and the second is the 2011 Japanese Tsunami that devastated the island of Honshu, one of Japan’s main islands.

In this lab, we will have a guided discussion about the impact of the March 11, 2011 tsunami on the landscape of northern Japan. We will do this by observing historical imagery on Google Earth and looking closely at images from before and after the tsunami. This is a great opportunity to study the extent and severity of the damage by the tsunami because there are many images from before and after the tsunami struck, the resolution is excellent, and there is only moderate cloud cover, so you can avoid it easily.

The goal of your observation is to determine what features you can use, both natural and human-made to determine: (a) how far inland the tsunami traveled in two different regions, and (b) how severe the damage was. As in Module 1, what I am looking for is original, thoughtful input as well as engagement in discussing other students’ ideas. First I will describe what you will need to do in Google Earth and then how you will input your ideas in the Discussion Forum.

Google Earth Observations

Open Google Earth and enter one or more of the following names in the search field:

1A. Minamisoma, Fukushima, Japan

1B. Iwaki, Fukushima, Japan

2A. Watari, Miyagi, Japan

2B. Miyagi, Japan

We will be looking at two regions, between Minamisoma and Iwaki in Fukushima Prefecture, and between Watari and Miyagi in Miyagi Prefecture.

We will be looking at features in these two locations and comparing them. It is recommended that you start observing at an elevation of 15,000 feet (4.5 km), but be ready to zoom in closer when you see something interesting. Next, turn on the historical imagery button on the upper toolbar (the clock). Look closely at images before March 11, 2011, and after. There are numerous images of the days after the tsunami struck, and you may need to look at several days to avoid clouds, breaks in the image, and darkness. It’s also easiest to start near the coast and move inland. Look at natural features as well as structures and vehicles, and notice changes between pre- and post-tsunami images.

Discussion

1. Use Word or another text editor to respond to the prompt with your thoughts backed up with locations from Google Earth (Lat. Long coordinates and elevation - record as best as you can). The length of your response should be between 150 and 200 words. Pick one specific area in each prefecture (at least 2 places total) that was impacted by the tsunami. Compare the appearance of locations before and after the tsunami. Your response must include at least one location in each of the two prefectures (a total of two minimum). Look for natural features such as rivers, shorelines, forested areas, etc., to analyze the impact of flooding. Look for human-made features such as roads, houses, businesses, ports, agricultural fields, farms, etc., to analyze the impact of flooding. Be sure to write the coordinates of the places and note the distance from the coastline to discuss how far inland the tsunami waves traveled. Do you notice differences between the two prefectures? We recommend typing your response in Word or another text editor and then copying/pasting it to the discussion forum to avoid losing your work midstream in the event of an accidental browser closing, intermittent Internet connectivity, etc.).
2. Go to Module 7 Lab (Discussion) and type or copy/paste your response to the prompt into the text box marked 'reply' and select Post Reply by 11:59 p.m. on Thursday to allow time for responses. Your response is now visible to your classmates and your instructor.
3. Read through others’ responses and write a thoughtful reply to at least two other students by the date listed on the calendar. These replies should be either a rebuttal in which you add your ideas in the form of a persuasive argument (written with respect for the originating author) or a response that agrees with, supports, and builds upon the original response. Because a timely response to the conversation is part of your grade, subscribing to the forum is required. Check in to the discussion forum often throughout the week to post and respond to comments. Your response to at least one other classmate should be posted by 11:59 p.m. on Sunday to allow for authentic discussion.

Grading

The grading rubric will help you understand what constitutes an appropriate level of participation on your part. The instructor reserves the right not to award any credit (including points for timing and interaction) if the content of the posts (however on-time they may be) is off-topic, offensive, or otherwise inappropriate. Such posts may be deleted at any time by the instructor.

As you have learned first-hand from the data presented here, tsunamis have the capacity to flood low-lying coastlines and can push waves of water inland for hundreds of meters, if not several kilometers, under the right geographic conditions. In the images studied on the website and historical imagery on Google Earth, it is easy to see how far inland the tsunami impacted.

By studying a case example like this catastrophic event, geoscientists collect incredibly important information that is absolutely critical in helping to develop plans for mitigating and or adapting to similar events that will occur in the future. Unfortunately, the findings often don’t get to people on the ground until years, if not decades, after such events – sometimes, after rebuilding has taken place. You may have noticed in the reading that large tsunamis are relatively infrequent with some happening decades apart; however, you may have also seen where they can also be more frequent as in the case of the 1960 Chile and the 1964 Alaskan events, or the 2004 Sumatra, the 2005 Sumatra, and the 2007 Sumatra earthquakes. Suffice it to say that it is critical that the general public becomes educated on the topic. Moreover, it is also important for government agencies and political leaders to act on these data and become active in the process of helping to protect life, resources, and infrastructure in new and creative ways, so we can avoid such catastrophic loss of life in the future. Hopefully, the materials covered here will lead you to an understanding of the complexities of providing communities with early warnings to protect lives and property.

Tsunamis are unpredictable, and because of their unpredictable nature, tsunamis are incredibly damaging when they occur and are very challenging to mitigate and adapt to even in the most technologically advanced countries of the world. Imagine, if one of the world’s most technologically centered societies can be rocked to its core by an event of this magnitude, what can and will happen in the future in countries like the U.S. when we are impacted again? Will our outcome be similar to or possibly even worse than the event that impacted Japan? For much of the U.S. population, the risks are perceived to be relatively low because of the minimal plate tectonic activity along the eastern seaboard in the Atlantic. However, geoscientists are still concerned about a number of high-risk areas, including the Cascadia region of the Northwest coast. What do you know about risks for tsunamis in the area that you live, vacation, or are interested in studying?

• Students will develop an understanding of the mechanics of coastal erosion, and develop the fundamental geospatial and quantitative skills and concepts needed to assess coastal erosion rates.
• Students will learn about various classical coastal engineering methods for mitigating coastal hazard risks and be introduced to new alternate options for mitigating coastal hazard risks.

Learning Objectives

By the end of this module, students should be able to:

• examine the mechanics of the erosion process through the concept of a sediment budget in a coastal cell;
• observe erosion along a coastline from sequential Google Earth images;
• describe and critique a variety of methods used to mitigate coastal erosion;
• explain and contrast innovative approaches to coastal hazard mitigation and describe some alternatives and where they are used presently;
• differentiate between soft versus hard mitigation strategies and state advantages and disadvantages associated with each.

Module 8 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

Introduction

Coastal erosion is a natural phenomenon that can be exacerbated by human activities and by storms and tsunamis. In Modules 2 and 3, we briefly touched on the natural processes of coastal erosion. We discussed the role of sediment movement and deposition in the evolution of coasts. We have also mentioned that barrier islands, an important protection for inhabited coastlines, are diminishing in size worldwide due to lack of available sediment and sea level rise. We also discussed the deterioration of the world’s deltas, including the U.S. Mississippi River delta, which is a classic example. In Modules 5-7, we looked at the erosional effects of storms and tsunami waves on coastlines, and in Module 11, we will look at specific examples of the effects of erosion and other coastal changes on the human landscape. In Module 8, we will examine the topic of coastal erosion from an engineering perspective, considering the forces at work on the shoreline and the rates of sediment gain and loss, which determine the state of the shoreline.

This shoreline is naturally retreating as winter storms in the North Sea erode the soft sediment of the cliffs. Towns such as Happisburgh are at risk as the sea cliffs erode.

We will consider the natural phenomena of coastal erosion and accretion and the human-induced changes on shorelines. We will weigh the pros and cons of the many engineering strategies (hard and soft engineering) that humans have devised to control shoreline changes. First, we will explore the concept of coastal erosion and the idea of the coastal cell by reading the article linked below.

What is coastal erosion, and when is it a problem?

Defining coastal erosion is rather straightforward. But to understand the phenomenon is far from easy. There is a widespread perception that coastal erosion is always irreversible, especially, for example, immediately after a storm event when erosion is more evident. This sometimes results in a call from both local residents and political representatives for hard engineering works to be constructed. There is little public awareness of the physics behind coastal processes that causes the difference between structural and episodic erosion. Few will know how natural coasts change due to fluctuations in forcing. And that erosion can be followed by coastal accretion when boundary conditions change, either at a seasonal, annual or much longer, geological time scale.
from Conscience-eu.net: What is Coastal Erosion and When is it a Problem?

Learning Check Point

Please answer the questions below.

Figure 8.3: Coastal erosion during a king tide, Dania Beach, Florida

Credit: Daniel Di Palma This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

While maps typically delineate the transitions between land and sea with clear lines, in reality, the coastline is much less well-defined. The position of the coastline through time is highly variable, from the daily fluctuations of the water’s edge at beaches due to tides to the shoreline advance or retreat over hundreds of kilometers with geologic-scale or climatic influenced sea level fluctuations. As you read in the ConScience article, the coastline position does not just depend on sea level; instead, the supply of sediments to the coast and the processes responsible for their redistribution within a coastal cell are both responsible for coastal evolution. Coastal erosion removes material from the shoreline and redistributes it to other parts of the coastal cell. While erosion is usually most drastic during extreme events with associated high surges and waves, shoreline erosion can also occur gradually over a longer time period due to sediment deficits.

In modern times (decadal timescales), many of the world’s coastlines are characterized by erosion (approximately 70% of the world’s sandy coastlines are retreating). This widespread erosion is due to a variety of factors, most notably:

• global eustatic sea level rise that has occurred over the past century;
• global reductions in the supply of sediment reaching the coast (due to sediment impoundment behind dams, urbanization, etc.);
• human engineering at the coast that restrict sediment movement (harbors, seawalls, groins).

Coastal erosion is a naturally occurring process that can be exacerbated and becomes a significant problem when the dynamic coastline impinges on the fixed human infrastructure and uses within the coastal zone. Despite the potential risk of coastal erosion or flooding within the coastal zone, the majority of the world’s human population resides there, and in fact, numbers continue to grow as people migrate to coastal cities. Coasts continue to support the economic centers of the world, while at the same time critically ecologically important and sensitive natural habitats are supported by coastal zones. Coastal zones support a wide variety of human land uses. Tourist resorts, fishing communities, farming, aquaculture, and other land uses all vie for space on the coasts of the world, and often come into conflict with each other and with the dynamic interface between land and water. While inland areas are undoubtedly less vulnerable to coastal hazards, the coastal zone has been historically rich in resources and uniquely suited to support economic activities such as trade, industry, and tourism, attracting settlement and migration despite the elevated risks.

The primary impact of human activities within the coastal zone is the displacement of natural habitat with development, an increasing problem with continued coastal population growth. This issue will be examined in detail in Module 11 case studies. In the following pages, we will examine more closely the mechanics of coastal erosion and the human engineering strategies employed around the world to mitigate coastal erosion to sustain human land uses on the coast. We will question each approach in terms of sustainability in the context of the dynamics of the coastal zone and the increased challenges related to climate change.

These land use change maps of Egypt's Nile Delta, which are shown in the link below, show change over 24 years, between 1990 and 2014. Comparison of the two maps reveals many changes to the land-water interface on this coast. As you compare the two images, you will notice that the human activities that impact the coastline, such as fish farming and urban areas increase in area. The area of natural coastal lands decreases in area. Almost all urbanized coastal zones around the world will show complex land use changes such as these over the past few decades.

Along much of the world’s coastlines, the intersection of vulnerability (e.g., high populations, economic activities supported by the coastal zone) and coastal hazards (e.g., coastal erosion, coastal flooding) produces a risk that is unacceptable to the particular community and society, requiring the use of coastal protection measures to reduce the risk. The following sections detail some of the typical “hard” and “soft” coastal protection measures and how they impact risk and the environment in the coastal zone.

As you have just discovered, humans have undertaken a wide range of initiatives to try and protect some coastlines and limit the amount of coastal erosion that is taking place. These initiatives include the construction of hard protective structures such as breakwaters and seawalls or the imitation of natural processes that include the placement of sediment in key locations or planting vegetation to stabilize loose unconsolidated sediment. The decision to use one method over another is extremely complex, requires a solid understanding of the system to be protected, and consideration of the economics and politics of a project.

Suppose, for example, that you own beachfront property and historically the beach in front of your house has been retreating landward, toward your house, at a rate of a meter per year for the last decade because of the combined effects of erosive storms and reduced sediment supply. On the basis of the historic trend, it is clear that within another decade the waves will be at your door. It is clearly, then, in your best interest to develop some sort of project that will help reduce the erosion and cause the beach to begin building seaward again. What are your options?

You could go to the local city council and suggest that a series of groins be placed along the beach in a location that will help trap sediment carried by longshore transport. For this to be effective, you would, however, need to have an excellent understanding of the longshore transport patterns on a daily and longer time frame. Placement of the groin in the wrong place could actually have a negative effect on the beach at your property (depending on the direction of transport) and enhance the erosion. Additionally, you would have to consider the impact of such a structure to the neighboring beaches. Do you think that your neighbors would advocate for structures to protect your beach if it would then also cause erosion in front of their properties? What about the cost of such a structure and who would pay for it? Projects such as this can cost millions or tens of millions of dollars, and you do not have the finances to cover the costs. So, who will pay for it? Suppose I am a taxpayer in a more landward located county. Do you think I would advocate for my taxes to be used to protect your beach-front property if the school my kids attend needs new technology and computers that are normally paid for by the same tax money?

In this example, numerous systems need to be considered, ranging from the natural longshore transport system to the local economic and political system. It is clear that situations such as this are extremely complex and require careful planning and implementation, and, in most cases, not everyone is content with the final outcome.

Introduction

The objective of this Lab is to help you develop an appreciation for coastal erosion and associated risks when placing major infrastructure proximal to coastal hazards.

Ocean Beach is a sandy beach backed by erodible bluffs that form the boundary between the western edge of the city of San Francisco, CA and the Pacific Ocean. Like many sandy coasts around the world, portions of Ocean Beach have experienced significant erosion in the past decades. The long-term erosional trend along the southern reach of the beach has been punctuated by periods of intense erosion during particularly severe winter El Niño storm seasons, when the beach and backing bluffs can be exposed to very high waves.

The situation is complicated by the presence of critical infrastructure within the coastal zone. The Great Highway, an important transportation link, is located on top of the bluffs backing Ocean Beach, and recent erosional events damaged parking areas and forced the closure of one direction of traffic for much of the storm season. More importantly, a large sewage tunnel runs under the Great Highway, transporting the city’s wastewater south to a treatment plant. Continued erosion threatens this piece of expensive, critical wastewater infrastructure, and it must be protected in the near term to prevent both the environmental consequences of a tunnel failure and the huge cost of relocation. During the most intense erosion episode during the 2009-2010 El Niño winter, the city constructed an emergency revetment of armored stone along the eroding bluff to protect the wastewater infrastructure; however, the use of “hard” coastal protection structures met stiff opposition from environmentalists and local regulatory agencies due to the inevitable loss of beach in front of the structure.

Lab Overview

After you thoroughly read the article “SPUR: The Future of Ocean Beach” (mentioned above, follow the steps in the Module 8 Lab Worksheet below.

Downloads/Resources

• Module 8 Lab Worksheet

Instructions

Before you begin the Lab, you will need to download the Lab worksheet. We advise you to either print or download/save the Lab worksheet, as it contains the steps you need to take to complete the Lab in Google Earth. In addition, it contains prompts for questions that you should take note of (by writing down or typing in) as you work through the Lab.

Once you have worked through all of the steps, you will go to the Module 8 Lab to complete the Lab by answering multiple-choice questions. The answers to questions on this Lab worksheet will match choices in the multiple-choice questions. Submit the quiz for credit.

In Module 8, you have learned about the various traditional "hard" structures used in coastal engineering for shoreline stabilization and flood protection. However, hard structures partially hinder the recreational use of the coastal zone and can cause adverse ecological effects within the coastal zone. Groins, and jetties in particular, interrupt longshore sediment transport, causing updrift accretion and downdrift erosion of the shoreline. Soft shoreline stabilization methods offer an alternative to hard structures by using environmentally friendly techniques that enhance ecological functions and allow natural processes to continue. In the activities, you viewed different coastal areas with erosional shorelines, learned how to measure the long-term erosion rates, and became familiar with some of the complications of real-world problems where choices between the use of hard or soft structures must be made.

Reminder - Complete all of the Module 8 tasks!

You have reached the end of Module 8! Double-check the Module 8 Roadmap to make sure you have completed all of the activities listed there before you begin Module 9.

Students will be introduced to ideas of managed retreat and relocation of communities in coastal environments due to repeated impacts from coastal hazards; they will consider the idea of multi-layered defenses and continue to examine the rebuild versus retreat debate.

Learning Objectives

By the end of this module, students should be able to:

• investigate alternative methods for non-structural shoreline hazard mitigation, including managed retreat and multi-layered defenses;
• explore the pros and cons, including cost-benefits of managed retreat case studies and consider examples of communities facing retreat as an option and the factors leading to these decisions;
• analyze hypothetical storm surge impacts on communities on the Louisiana coast using Google Earth and online tools.

Module 9 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

After Super Storm Sandy devastated the New Jersey coast and flooded coastal New York, including parts of Manhattan, the debate about rebuilding in place or implementing more sustainable coastal hazard mitigation practices has raged in the U.S.

The traditional practices in the U.S. and in other countries around the world have been to armor the shorelines and replenish beaches to prevent or mitigate erosion. Here in the U.S., recovery from flooding has relied on programs such as the National Flood Insurance Program, the Federal Emergency Management Agency (FEMA), and others, to allow home and business owners to rebuild.

Around the world, there is a growing recognition that hard structure protection and rebuilding in place are not sustainable practices, especially as we become increasingly aware that storms of Sandy and Katrina magnitude may be occurring more frequently with our changing climate. Greater emphasis is now being placed on coastal communities developing better resilience to repeated coastal flood events and sea level rise.

Following the devastation of Sandy in the northeast, some geologists weighed in on the debate to advocate alternatives to rebuilding, such as managed retreat. Here, we will take a look at some ideas from one leading group of coastal scientists, led by Orrin Pilkey, who has spent his career thinking and writing about how to live with dynamic shorelines. Here, he is vocal in making the call that there needs to be a change in policy in the U.S. when it comes to trying to combat catastrophic flooding along our coasts. The case study focusing on rebuilding after Sandy on the Jersey Shore in the reading "Rebuild or Retreat from the Jersey Shore", in which a piece from WNYC follows homeowners debating on the future of their community after Sandy, highlights once more the dichotomy of opinions about the need to retreat from the shoreline versus the need to maintain a lucrative tourism and vacation home economy by holding things in place, at least for now.

Learning Check Point

While this Learning Check Point is not for credit, you will be expected to know the material for the Module 9 Quiz.

Please take a few minutes and answer the questions below.

In the readings on the previous page, much of the thinking was in response to a catastrophic event, such as Hurricane Sandy. On the Jersey Shore, the emphasis has been on building higher dunes to mitigate the problem of coastal hazards threatening human infrastructure. However, as the coastal scientists point out, dunes and other beach features have a tendency to migrate landward. As sea levels rise, this natural migration will accelerate. Options that involve working with these natural processes rather than trying to control them involve a longer-term approach and, as we have seen, can be controversial. We will look at some examples of places where these alternative methods have been employed using the principles of managed retreat or managed realignment, which are in contrast to the more reactionary approach of rebuilding structures in place and protecting them with dunes and other engineered lines of defense.

Managed retreat or managed realignment is a coastal management strategy that allows the shoreline to move inland, instead of attempting to hold the line with structural engineering. At the same time, natural coastal habitat is enhanced seaward of a new line of defense. This approach is relatively new, but is gaining traction among coastal policymakers and managers in the face of increased coastal hazard risks. There is a growing recognition that attempting to “hold the line” in many places is a losing battle.

In many cases of managed retreat, human development is “moved” out of harm’s way and natural areas are restored to enhance their ecosystem services. Typically, flood defenses are set back from the shoreline, and flooding is allowed in the previously defended area. Usually, natural coastal habitat is preserved seaward of the man-made defense, and it provides extra protection or a buffer from flooding.

Managed retreat can be complex and often contentious, as it can include delineating a new line to which structures can be built and home and business owners must be bought out.

Components of managed retreat may include:

• coastal planning;
• relocation and buy-back and buy-out programs;
• regulating types of development allowed;
• designating no-build areas;
• habitat restoration;
• replacement of built environment with green space.

For managed retreat or managed realignment to be successful, a number of criteria or conditions must be met, according to authors Gardiner et al., and Rupp and Nicholls. These are listed below. Perhaps points 4-6 are the criteria that are lacking most often. As we will read in the following case studies, few managed retreat projects are accomplished without controversy and lengthy debate. In places where the level of development on the shoreline is high, managed realignment may not be an option at all, at least in the present conditions.

"Six of the most important conditions are given below (Gardiner et al., 2007; Rupp-Armstrong and Nicholls, forthcoming):

1. presence of coastal defenses
2. availability of low-lying land
3. desire or need to improve flood or coastal defense systems
4. presence of a sustainability-oriented coastal management attitude
5. desire or need to create intertidal habitats
6. societal awareness about the benefits of managed realignment"

In this module, we will explore examples of managed retreat in the U.S. and the U.K. to gain an understanding of the complexities of implementing these projects. We will also consider the discussions of managed retreat options in large cities that are particularly vulnerable to inundation.

In addition, we will look at the dilemma of whole communities facing decisions to relocate in the face of repeated flooding, as well as other mitigation measures such as elevating homes and changing building codes.

Learning Check Point

Objective

Investigate alternative methods for non-structural shoreline hazard mitigation, including managed retreat and multi-layered defenses.

While this Learning Check Point is not for credit, you will be expected to know the material in Module 9 Quiz.

Explore the examples of managed retreat in this ArcGIS Story Map, created by Virginia Institute for Marine Sciences: After reading, consider how you would answer the questions on the cards below. Click "Turn" to see the correct answer on the reverse side of each card.

California Coast

On this page, you will visit two locations on the California coast where the process of managed retreat has been used to address shoreline erosion problems. In the first example, at Ventura Beach near Santa Barbara in southern California, stakeholders worked together to find a solution to a chronic shoreline erosion problem. In the second example, at Pacifica Beach near San Francisco, wetland and riparian habitat were enhanced while at the same time moving structures out of the way of flooding and erosion. As you will see, both examples are in locations that have a medium level of human development, a motivated group of residents, and diverse stakeholders who collaborated to produce and execute a long-term plan. Both areas are in economically healthy areas, which makes raising funds more feasible. However, none of these things are easy to accomplish. These small-scale, less than ten-acre projects serve as valuable learning experiences, but larger-scale projects of similar kinds will likely need to be implemented in the near future, on the scale of, for example, Ocean Beach, which you studied in Module 8 Lab.

In the Ventura Beach example (Climate.gov - Restoring Surfer's Point), Surfers' Point Shoreline Managed Retreat Project is described and illustrated. The article outlines the challenges that had to be overcome to find consensus among the many stakeholders, with the project taking a decade to come to fruition. The stakeholders found that "Focusing on goals they had in common and identifying a bounded problem helped the groups converge on a single solution strategy. The decision to retreat from the ocean—pulling existing structures inland to make room for natural beach processes—allayed concerns that a hardened solution such as a seawall would degrade conditions for surfing, opened opportunities to rehabilitate the beach ecosystem, and enhanced the natural protection of assets on land." In this example, the road and parking areas are moved back and the beach and dunes widened. Volunteers planted native vegetation on the dunes, which serve as natural habitat and protection for the human structures behind the beach.

Restoration and Managed Retreat of Pacifica State Beach examines the Pacifica Beach effort to create climate change coastal community resilience. At Pacifica Beach, the managed realignment project is touted as a success.

The U.K., being a relatively small island nation with a dense population, has a somewhat different approach to coastal management than the U.S. As a result, managed retreat, or managed realignment as it is called in the U.K., has been under serious consideration for a longer period of time than in the U.S. In the winter of 2013 -2014, tremendous storms caused extensive coastal flooding, bringing coastal management to the forefront.

Ecosystem Services of Coastal Marshes

Research shows that natural coastal marsh habitats provide many ecosystem services, including attenuation of storm surge. Attempts to quantify the amount of protection provided by coastal marsh has been elusive, but researchers conclude that “It is clear that coastal management decisions should consider the dynamics of natural coastal systems previous to human modification and be cautious about any actions that erode the natural benefits and ecosystem services provided by salt marshes.” (Shepard et al., 2011). This statement is based on the fact that research strongly indicates that coastal marshes play a very important role in protecting human infrastructure from coastal hazards, including sea level rise and storm surges. (Reference: Shepard CC, Crain CM, Beck MW (2011) The Protective Role of Coastal Marshes: A Systematic Review and Meta-analysis.)

Hurricane Sandy came ashore on the New York/ New Jersey shoreline on October 29, 2012. This late-season storm was dubbed “Superstorm Sandy” because of its massive size and because it coincided with a spring high tide (full moon), which exacerbated the height of the storm surge. The massive storm surge inundated a large swath of the coastline, which includes New York City. Parts of the New York Subway system were flooded, widespread power outages crippled the city, and low-lying neighborhoods were destroyed across the region. The statistics for New York alone sum up the storm’s magnitude:

• 43 deaths - 23 of whom perished on Staten Island.
• $19 billion in damages
• 90,000 buildings in the inundation zone
• Nearly 2 million people without power

The size of the area inundated is illustrated by the FEMA flood map image below.

Map of area of inundation by Hurricane Sandy’s storm surge. The map includes parts of both New York (including Manhattan Island) and New Jersey.

Credit: FEMA via WNYC John Keefe, Steven Melendez, and Louise Ma from the WNYC Data News Team. Help with the New York state zone shapefiles from Andrew Hill at Vizzuality. Flooding Survey based on Nov. 11, 2012, interim data from the FEMA Modeling Task Force Hurricane Sandy Impact Analysis, which combines detailed elevation data with U.S. Geological Survey inspections of high watermarks. Flood Zones Coastline inundation zones are calculated by the U.S. Army Corps of Engineers using worst-case storm, wave, and tide calculations, together with elevation data. View the New Jersey hurricane evacuation studies and the New York state evacuation studies. In New York City, the state zones are superseded by the city's own evacuation zones, which draw from the USACE surveys. (Public Domain)

Sandy’s massive impact on such a densely populated and economically important region of the United States precipitated an unprecedented response by area leaders. Both New York Governor Cuomo and former New York City Mayor Bloomberg have taken strides to encourage residents to consider the future of New York’s coast in light of sea level rise predictions.

Former Mayor Bloomberg and the New York City Government were proactive in the development of the NYC: Special Initiative for Rebuilding and Resilience which produced a comprehensive report calling for a “stronger, more resilient New York”. Recommendations found in the report include a multi-faceted approach, including flood protection systems (levees, floodwalls, floodgates, etc.), as well as the designation of certain areas to be set aside as green space. It takes into account the fact that 25% of the city is flood-prone and that sea level rise will only make matters worse.

New York Governor Cuomo, meanwhile, initiated a buyout program for homeowners whose homes were in areas likely to experience repeated flooding. This buyout program has been successful, particularly in Staten Island and in other New York neighborhoods especially hard hit by Sandy. Areas are being returned to green space rather than being rebuilt. Case studies are featured in this module.

A slightly different approach to managed retreat is sometimes necessary in the face of a natural disaster. So, rather than using the types of managed retreat projects described in the previous section, that are carefully planned and take place in discrete locations, moving homes and businesses to safer locations urgently comes to the forefront as we saw in Unit 2. In these cases, decisions are often made quickly and are driven by economic necessity.

Hurricane Sandy Recovery: Staten Island’s Fox Beach Community.

Following a natural disaster caused by a storm such as Sandy, a different approach to retreat is often considered. In this case, rather than using the managed retreat projects described previously in this module, which are carefully planned and take place in discrete locations with a long-term vision, the action of moving homes and businesses to safer locations urgently comes to the forefront. In these cases, decisions are often made quickly and are driven by economic necessity and the availability of funds resulting from the disaster itself.

Learning Check Point

Government Buy-Out of At-Risk Coastal Properties – New York Example following Sandy

Objective: Investigate alternative methods for non-structural shoreline hazard mitigation, including managed retreat and multi-layered defenses.

Although this Learning Check Point is not for credit, you will be expected to know the material in the Module 9 Quiz. Once you read and understand the articles referenced above as well as the excerpt below, take a few minutes to answer the questions about the New York Home Buyout Program in the space provided.

Government Buy-Out of At-Risk Coastal Properties – New York Example following Sandy

Excerpted from a March 2013 press release from New York Governor Andrew Cuomo’s Office:

Recreate NY Smart Home Buyout Program - $171 million: Certain areas are at high risk for repeated flooding, causing damage to homes and risking the lives of residents and emergency responders. To reduce those risks and provide residents with an opportunity to leave their properties, New York State will offer voluntary Buyouts for homes that were:

• substantially damaged inside the 500-year flood plain, or
• located within designated buyout areas where damage has occurred and where property may be susceptible to future damage due to sea level rise and other factors. These enhanced buyout areas will be selected in consultation with county and local government officials.
• In very high-risk areas, there will be a prohibition on rebuilding and these areas will be used as buffer zones. Under the state's proposal, and subject to approval by HUD, re-development of property outside of the 100-year floodplain that is acquired through a buyout would be permitted, so long as the new structure is built to mitigate future flood impact. Homeowners will be notified if they are eligible for a buyout after HUD has approved this plan.

Definition for "500-year flood plain" and "100-year flood plain"

A "100-year flood" is not a flood that will occur once every 100 years. Instead, it should be thought of as flood elevation that has a 1-percent chance of being equaled or exceeded each year. Therefore, a 100-year flood could occur more than once in a relatively short period of time. A 500-year flood elevation has a 0.2% chance of being equaled or exceeded in any given year.

If the trend of more frequent storms and increased sea level rise continues, these types of solutions will likely become more common. Who will foot the bill to move coastal communities? Will it happen only after disasters, or in a more planned way? In the case of Isle de Jean Charles, government funding was found in the form of a grant awarded to relocate the entire community. However, many challenges have plagued even this small-scale relocation project. We saw that long-term planning was lacking in Ocean Beach, CA. What will the approaches to these dilemmas be in 10 or 15 years from today? These are questions for us to ponder at this point. Policymakers, planners, community leaders, and politicians will have to quickly find solutions to these challenges for many communities soon.

Coastal Louisiana is home to hundreds of small communities, as well as several larger towns (such as Lafitte, Houma, and Thibodaux), that are not protected by the large federally subsidized hurricane protection levees such as those that surround New Orleans. The new hurricane protection system for the area, that is currently under construction, cannot incorporate all of these communities, although the Morganza to the Gulf levee* when it is completed, will include the larger towns listed here. One community that will not be included is the small town of Isle de Jean Charles in Terrebonne Parish. This small, mostly Native American community is grappling with relocating and creating a new community after receiving federal funds for resettlement.

Video: Isle de Jean Charles from the documentary LAST STAND ON THE ISLAND (11:23)

As the short film below will demonstrate, not all the residents agree with Chief Naquin’s decision.

Isle de Jean Charles Resettlement Story

The Isle de Jean Charles residents have long been aware that the island's days are numbered as sea level rises and erosion of the marshes continues. Their houses are flooded and damaged regularly. Even so, many residents are resistant to the idea of leaving the island because of their strong attachment to the land and the way of life, including living off the water by fishing, shrimping, and crabbing. In 2016, the community of Isle de Jean Charles was the recipient of a $48 million grant from the Department of Urban Development - HUD to relocate the families of the "Island" to a safer location, 40 miles inland near the community of Schriever. This is the first time a community has received federal funding and support for a relocation of this kind. The resettlement plan, which is still in progress, has not progressed smoothly. The original intention of tribal Chief Albert Naquin was to keep the tribal community intact and create a new community that allowed displaced members who had previously left the island to rejoin the community. There are many details and concerns to be worked out between the tribe and the state. To date, 23 families have committed to relocating to the new community. Others are staying behind. The actual move is still several years ahead. The difficulties encountered highlight how challenging relocating a community can be, especially if the community wishes to stay intact. The dilemmas and challenges met by Isle de Jean Charles are likely to play out in many places as sea level rise claims other coastal communities.

Learning Check Point

The resettlement website has details of this plan and a video in which Chief Naquin and others outline the plan. Read the articles and watch the video on Isle de Jean Charles to help you understand the dilemma faced by such a small, tight-knit community. Consider how you would answer the questions on the cards below. Click "Turn" to see the correct answer on the reverse side of each card.

The Community of Isle de Jean Charles, LA.

Credit: Gary Allen

Louisiana is an example of a very low-profile coastal area characterized by relatively newly deposited delta sediment (less than 10 thousand years) of the Mississippi River delta. Land loss has been ongoing at a rapid pace over the past century, peaking in the late 20th century, and is currently occurring at a rate of approximately 10 – 20 square miles per year. The communities in coastal Louisiana are all at risk of storm surge inundation, to varying degrees. We have already looked at New Orleans in detail and seen that it has a system of flood defenses recently upgraded after Hurricane Katrina. Many smaller communities that are located close to the Gulf of Mexico have no protection from federally funded flood protection. Many have levees built and maintained at a parish level. New federally-funded hurricane protection levees, such as the Morganza to the Gulf levee system are planned to protect towns such as Houma and Thibodaux. It is approximately 100-mile-long levee that averages 6 meters (20 ft) in height. But some small communities such as Cocodrie and Isle De Jean Charles will not be within the footprint of this levee. It is not feasible in terms of available funding and engineering options to protect some communities. This presents a dilemma for many communities.

Louisiana's Coastal Master Plan and Multi-layered Protection

Levees are not the only form of protection for coastal communities. Louisiana’s Coastal Master Plan incorporates the concept of a multi-layered defense system that includes maximizing the flood mitigation potential of barrier islands, marsh, and natural ridge restoration projects, (many of which involve pumping sediment from a designated location, often from the bottom of the Gulf of Mexico), as well as the use of fresh water and sediment diversions from the Mississippi River to build new land.

What is Multi-layered Protection?

A clear explanation of the concept of Multi-layered protection is presented by the Lake Pontchartrain Basin Foundation outlined at Multiple Lines of Defense Strategy. This conceptual approach identifies eleven “lines of defense”, which work in concert to ameliorate the effects of a storm surge by creating friction and reducing storm surge and wave height as it moves inland across the low-lying delta land. This plan was published and incorporated into Louisiana's Coastal Master Plan in the years after Hurricane Katrina. The eleven layers of protection are shown in the diagram below:

• Offshore shelf
• Barrier islands
• Sound
• Marsh land bridge
• Natural ridge
• Highway
• Flood gate
• Levee
• Pump station
• Elevated buildings
• Evacuation route

Multiple lines of defense schematic.

Credit: Lopez, John A., 2006, The Multiple Lines of Defense Strategy to Sustain Coastal Louisiana, Lake Pontchartrain Basin Foundation, Metairie, LA January 2006.

Video: FPA East Virtual Tour (16:06)

This is a virtual tour of the 17th St Canal Pump Station and the Surge Barrier in New Orleans. The first part focuses on Hurricane Katrina's destruction, while the second part showcases the flood protection system: Hurricane Storm Damage and Risk Reduction System (HSDRRS).

Learning Check Point

Please take a few moments to think about what you just learned then answer the following questions to test your knowledge.

Introduction

The objective of this Lab is to explore a low profile coastal area in Louisiana and use tools in Google Earth to measure the slope and evaluate the protective potential of the coastal wetlands and man-made levees separating the coastal communities from the Gulf of Mexico

For this Lab, you will be using Google Earth to explore the coastal area of Isle de Jean Charles and use data from a storm surge model to analyze the potential impacts of storm surges on this and nearby communities. You will consider the protective functions of the coastal marshes as well as the new hurricane levee that is designed to protect some communities but not Isle de Jean Charles.

Lab Overview

After you thoroughly read the U.S. Army Corps of Engineers fact sheet about the Morganza to the Gulf levee project (mentioned above), follow the steps in the Module 9 Lab Worksheet below.

Downloads/Resources

• Module 9 Lab Worksheet

Instructions

Before you begin the Lab, you will need to download the Lab worksheet. We advise you to either print or download/save the Lab worksheet, as it contains the steps you need to take to complete the Lab in Google Earth. In addition, it contains prompts for questions that you should take note of (by writing down or typing in) as you work through the Lab.

Once you have worked through all of the steps, you will go to the Module 9 Lab. to complete the Lab by answering multiple-choice questions. The answers to questions on this Lab worksheet will match choices in the multiple-choice questions. Submit the quiz for credit.

In Module 9, you investigated alternatives for coastal hazard mitigation, including managed retreat and multi-layered protection. You considered the pros and cons of managed retreat versus traditional solutions such as structural protection. You used online tools to make measurements of bed slope on the Louisiana coast in order to estimate storm surge impacts on a real community. You took into consideration the physical, social, and economic challenges that face coastal managers today to make recommendations for the future for a coastal community in Louisiana.

Reminder - Complete all of the Module 9 tasks!

You have reached the end of Module 9! Double-check the Module 9 Roadmap to make sure you have completed all of the activities listed there before you begin Module 10.

Students will develop an understanding of concepts of building with nature, and old and new smart building practices used for flood control, hazard mitigation, and risk reduction.

Learning Objectives

By the end of this module, students should be able to:

• distinguish and evaluate various smart building and building with natural approaches;
• evaluate and recommend smart building approaches for the expansion of a case study city that is threatened by sea level rise and storms;
• employ building with nature and layered defense approaches in consideration of the smart building design in the case study;
• examine recent trends in smart building along coastlines and integrate concepts of resiliency and coastal flood protection through methods such as massive nourishments.

Module 10 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

The concept of smart building or building with nature is not new. Early settlers, cities, and communities living along river banks, deltas, and along coastlines have adapted their lifestyle to the pulsing and cyclic forces of nature. From fluctuating sea levels to seasonal flooding, to storm flows, these communities slowly built resilience and developed methods to help them withstand the elements to maintain a way of life. Communities were founded or expanded along high ground; evacuated low-lying areas in river valleys during floods; fled during storms, or learned to live with water, often creating floating infrastructures. We will now explore some basic early smart building approaches by visiting low-lying and delta communities in the United States, the Netherlands, and the Mekong Delta in southwestern Vietnam.

City Expansion and Smart Considerations

Despite the high risk of exposure to coastal hazards of increasing intensity and frequency, most of the world's populations, economic activities, and infrastructure continue to be located along the coast. In many cases (see Module 9), retreat and abandonment of high-risk areas is simply not an option. Already growing populations, augmented by immigration, in major coastal cities requires thoughtful planning to protect against flooding without hindering the many valuable ecological functions within the coastal zone. The following sections detail several smart building measures that have satisfied the need for growth in coastal zones.

Mitigating Risks While Preserving Natural Processes

The simple concept of sediment supply along the coast and the unified concept of the coastal cell can be applied to other systems. For example, similar to the way a groin disrupts sediment transport downdrift of the structure, resulting in downdrift erosion until sufficient bypassing takes place, land reclamation practices, and the construction of levees, seawalls, and other storm protection structures including gates have their effects. On the one hand, land reclamation in tidal systems can alter the tidal exchange of water between the interior basin and the coastal ocean, and may yield sedimentation issues within the basin and near the tidal inlets. On the other hand, erosion within the basin, such as wetland loss, may have the opposite effect, resulting in widespread erosion at the inlets and sediment export due to the increase in tidal exchange. Levees that enclose open or semi-enclosed basins disrupt water, sediment, and nutrient exchange and may adversely affect submerged and intertidal habitat, including fish and other aquatic organisms.

Climate change sea level rise will continue to erode coastlines throughout the world for decades to come, and during these transgressive times, we cannot afford to be working against nature. This means that we must first understand the underlying processes governing the transport in the system experiencing these erosional cycles, determine accretion cycles, if any, and establish the best approach. Hardening the shorelines by seawalls and levees often implies a permanent boundary. Recall that sea levels rise and fall over geologic time with coastal imprints that span over generations; therefore, if we do not deal with issues now, the next generation will have to. Best approaches, for the most part, imply that we turn to soft, process-driven nourishment of eroding coasts that utilize natural processes – as opposed to mechanical placement – for the distribution of materials. Often these soft methods are the least disruptive to nature, including local and proximal ecosystems.

But we cannot protect cities by nourishment methods alone. In many cases, the installation of levees and other flood control structures will be necessary, especially if cities are already established. The relocation of cities or portions of cities will have catastrophic economic influence. When floodgates are needed, modern designs that utilize natural processes will be favored. An example we saw in the video from the Netherlands is the installation of gates that remain open most times to allow for tidal exchange and facilitate small changes in tidal range to maintain ecosystem function, closing only when cities are threatened by storms. Coupled with layered defenses, a concept introduced in Module 9, smart building in many cases can afford the needed protection while helping to lower future energy demands and maintenance costs and achieving overall higher ecosystem services and functions.

The following five case studies will help you learn about how some communities have built with nature to mitigate risks while preserving their natural resources.

Development of Smart Building for a Rapidly Growing Coastal Community (Tampa Bay, FL)

Objective

The objective of this activity is for you to explore smart building measures for a city that is threatened by sea level rise and storms.

Background

A group of cities surrounds Tampa Bay, FL, a bay/estuary along a tectonically inactive, trailing margin coastline. The coastline surrounding the bay inlet is composed of sandy beaches and barriers, and elevations range from lowlands near mean sea level to Pleistocene uplands of over 10 m. This coastal region is exposed to tropical storms and hurricanes that can produce storm surges of several meters above mean sea level.

You will read more about the background of this Lab in the Module 10 Lab Worksheet.

Downloads/Resources

• Module 10 Lab Worksheet

Instructions

Before you begin the Lab, you will need to download the Lab worksheet. We advise you to either print or download/save the Lab worksheet, as it contains the steps you need to take to complete the Lab in Google Earth. In addition, it contains prompts for questions that you should take note of (by writing down or typing in) as you work through the Lab.

Once you have worked through all of the steps, you will go to the Module 10 Lab to complete the Lab by answering multiple-choice questions. The answers to questions on this Lab worksheet will match choices in the multiple-choice questions.

In Module 10, you learned how smart building can help reduce the vulnerability of coastal populations exposed to increasing threats due to growth and global climate change. In case studies, the smart building of early settlers, cities, and communities was shown, where smart building methods included settling on natural levees, artificial mounds, and building floating cities. In recent times, the increasing coastal populations and economies have required more extensive protection works. The "Deltaworks" in the Netherlands protect the mostly-below-sea-level country from floods with massive engineering structures; however, later designs were altered to protect the vital estuarine habitat. Settlement in New Orleans was originally concentrated along the relative high-ground of natural levees; with advances in pumping technology, former backswamp areas could be settled, setting the stage for the Hurricane Katrina levee failures and flooding disaster. "Building with Nature" is a culmination of smart building principles, incorporating natural coastal processes and soft stabilization principles to reduce flooding risk, while enhancing recreation and ecology. As made clear in the assessments, smart building is often characterized by thoughtful development. If development doesn't create new risks, new risk mitigation measures will not be required.

Reminder - Complete all of the Module 10 tasks!

You have reached the end of Module 10! Double-check the Module 10 Roadmap to make sure you have completed all of the activities listed there before you begin Module 11.

• Students will assess the physical and social components of vulnerability to coastal hazards.
• Students will analyze worldwide case studies of coastal communities and their responses to coastal hazards in the context of vulnerability

Learning Objectives

By the end of this module, students should be able to:

Module 11 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

Let’s break down the concept of vulnerability to a coastal hazard into its components.

What Exactly is Vulnerability?

In terms of social science and natural hazards, vulnerability can be thought of as a three-dimensional construct.

The three dimensions of vulnerability we will explore are exposure, sensitivity, and adaptive capacity.

• Exposure is the degree to which people and the things they value could be affected or “touched” by coastal hazards.
• Sensitivity is the degree to which they could be harmed by that exposure.
• Adaptive Capacity is the degree to which the community could mitigate the potential for harm by taking action to reduce exposure or sensitivity. This can also be thought of as a measure of resilience. See below.

Take a few minutes to watch at least the first 4-5 minutes of this short video focusing on the immediate aftermath of Hurricane Katrina in New Orleans and coastal Mississippi.

Video: Hurricane Katrina Survivor Clung to Trees as House Fell Apart: Part 2 (8:32)

Knowledge Check Point

People and Things They Value

What is meant by the expression “people and things they value”?

This expression not only refers directly to people’s lives, livelihoods, and things of economic value, but also to places and to cultural, spiritual, and personal values. Also included are critical physical infrastructures such as police, emergency, and health services buildings, communication and transportation networks, public utilities, and schools, and daycare centers. It also refers to social infrastructures such as extended families, neighborhood watch groups, fraternal organizations, and more. The expression even includes such social factors as economic growth rates and economic vitality.

A community may be highly vulnerable to a low impact coastal hazard because of high sensitivity or low adaptive capacity – for example, a densely populated, impoverished neighborhood built on a low-lying shoreline could be easily inundated with a minimal flood from storm surge or tsunami and, due to the challenges imposed by poverty, they have great difficulty recovering from this event.

Another community can have a lower vulnerability to even high-impact coastal hazards because of low sensitivity or high adaptive capacity – for example, a wealthy tourist destination built to withstand flooding from storm surge may suffer a temporary setback when hit by a major hurricane but would be more likely to have the resources to rebuild than a low-income neighborhood would.

Therefore, coastal hazards can result in highly variable impacts because of these variations in vulnerability in time and space.

Disadvantaged groups of people are inherently more vulnerable to coastal hazards than others. The poor, the very old or very young, the sick, and the physically or mentally challenged are often vulnerable. Those lower educational attainment, or non-native speakers, are also often more vulnerable than native language-speaking people with higher levels of education. In the U.S., communities of color in coastal settings are often highly vulnerable, for example, this was true in New Orleans during Katrina and Puerto Rico during Maria. Vulnerable people may fit into more than one group. For example, the most vulnerable of a community could possibly be the minority, elderly, non-native speaking women.

Risk

What is Risk? Risk is the result of interaction between the components of the hazard and the vulnerability of the place that is impacted. Residents of a particular coastal community may weigh the risks of staying there versus relocating, or a person considering purchasing a house in a coastal community would definitely need to think about the risk to the property and his or her family and possessions. As we considered in our first exercise in Module 1, insurance companies account for all components of risk when determining insurance coverage. As the risk of devastating hurricanes has increased in the last decade, premiums have risen drastically in places such as South Florida. Below is a simple diagram summarizing the relationships between vulnerability, hazards, and risk.

Risk examples are obviously not restricted to coastal hazards. The descriptions above can be applied to other risks, such as serious illness during the COVID-19 epidemic. The risks of getting severely ill or dying vary greatly among different groups in a community, so that the elderly, those with underlying health conditions, and those living in group settings are at greater risk of severe illness from a COVID-19 infection than those who do not fit those demographics. Like other hazards, the disease has disproportionally affected minorities who tend to be poor and have more limited access to quality health care, so are more likely to suffer untreated underlying health conditions like high blood pressure and diabetes.

Diagram illustrating the connections between hazard, vulnerability, and risk

Credit: Dinah Maygarden © Penn State is licensed under CC BY-NC-SA 4.0

So, the question of why one place is more vulnerable to coastal hazards (or other types of hazards) relative to another does not have a simple answer. We must appreciate how the local frequency and intensity of these hazards interact with a diverse set of coastal processes, landforms, infrastructure, and social systems to harm people and things they value.

The question is important to policymakers because if governments and other coastal decision-makers are to make sound decisions to reduce the risk of all members of coastal communities to coastal hazards and prioritize spending to protect their most vulnerable people, places, and property, then they must understand where damage and suffering are likely to be greatest.

Resilience and Adaptive Capacity

The concept of resilience is important for understanding the adaptive capacity dimension of vulnerability to coastal hazards. The resilience of a community is its ability to use available resources to recover and grow from adverse situations, just as a resilient person can more easily bounce back from a setback than a less resilient person. Resilient communities can learn from past experiences and use that knowledge when confronting future problems. Systems with high adaptive capacity are therefore resilient and able to make the necessary changes to deal with coastal hazards. Systems with low adaptive capacity are much less resilient and much more vulnerable to coastal hazards. Later in the module, we will explore several examples of how communities with low adaptive capacity and poor resilience have coped with coastal hazards and how they have learned from these terrible experiences and are working to increase levels of resilience.

First, we will dig deeper into Vulnerability.

Figuring out the vulnerability of a person, place, or thing is a surprisingly complex task. To simplify this task, scientists have developed an assessment tool known as the Vulnerability Scoping Diagram (VSD). Moving from the center outward, the VSD defines the system being studied, divides vulnerability into its three dimensions (exposure, sensitivity, and adaptive capacity), defines components of these dimensions, and then assigns measures of these components. Each of these pieces of the VSD is described in more detail below.

General form of the Vulnerability Scoping Diagram (VSD).

Credit: Brent Yarnal © Penn State is licensed under CC BY-NC-SA 4.0.

Examples of VSD Explained

VSD showing some measures of the components of the vulnerability of the elderly to hurricanes in Sarasota, Florida.

Credit: Brent Yarnal © Penn State is licensed under CC BY-NC-SA 4.0.

The above figure shows an example of how the VSD can be used to assemble a holistic picture of the many different components that shape vulnerability to coastal hazards. This VSD shows the vulnerability of the elderly to storm surge in Sarasota, Florida, during the next decade. Starting with exposure, we see that the vulnerability of the elderly depends partly on the characteristics of the hazard itself – including storm surge, winds, and flooding – and partly on the location of the elderly relative to these hazards. The sensitivity of the elderly is a function of the age and income of the population, as well as their physical and mental health. The ability of the elderly to adapt to hurricanes – their adaptive capacity – is determined, among other factors, by how they perceive hurricane risks, the strength of their connections with family and friends (social capital), their access to living space outside of the hazard zone, and their education. Hence, elderly persons in Sarasota who are exposed to a large hurricane storm surge, are sensitive due to limited financial resources and poor health, and have few connections to friends or family, would be quite vulnerable. In contrast, elderly persons who are exposed to the same storm surge but are healthy and can draw on significant financial and social resources would be much less vulnerable. Note that while this example describes some important components of vulnerability to coastal hazards, a completed VSD will often include many more components than are listed here.

There are many ways to measure these components of the vulnerability of the elderly to storm surge. Computer models can simulate the likely extent and intensity of exposure to hurricanes’ rain, wind, and flooding; these simulations can be compared to observations from past storms, which can provide additional information about hurricane frequency and severity. Census data can show how many elderly persons are living in areas that are exposed to these hurricane hazards. Census data can also provide the measures of financial capital (household income), social capital, and living arrangement (number of persons per household), and educational attainment needed to assess these components of sensitivity and adaptive capacity. To measure other components (including physical and mental health or perception of hurricane risks), scientists may need to conduct their own surveys or request summaries of data sources that are not publicly available (such as the Sarasota County Registry of Persons with Special Needs).

Exposure is the degree to which people and the things they value could be affected or “touched” by coastal hazards.

Think about your favorite coastal location. What are the aspects of the natural and built (human developed) environment in that location that affect the likelihood that people or things they value will feel the impacts of a natural hazard there?

If the location is a house built on a beach on a barrier island such as the Outer Banks of North Carolina or South Padre Island in Texas, it is highly exposed to a potential coastal hazard, but it may be in a small community and the hazard (storm) may be low intensity. In this case, the exposure is not as high as, for example, if the location is New York City, and the hazard is a storm like Sandy. In this scenario, millions of people and things they value (including complex infrastructure and things of great cultural value) are exposed. Also, the hazard is high intensity, so this amplifies the exposure. This scenario is one of very high exposure.

The components one needs to consider when assessing exposure are as follows:

1. Hazard frequency and intensity

   In Modules 4 and 5 you covered both storm and tsunami hazards and read about the intense Hurricanes Katrina, Sandy, Maria, Harvey, Dorian, and several others. It is well established that climate change is resulting in storms of increased intensity, although there is less evidence that the frequency is increasing. However, in some locations in the world tropical cyclones are a relatively common occurrence, so can be considered frequent. The pattern of tropical cyclone frequency is illustrated in the animation shown here.

   Video: Hurricane Tracks Animation and Cumulative Map (00:14) No narration.

   Tropical cyclones have a wide range of wind speeds that are used to classify their intensities. NOAA’s National Climatic Data Center has assembled the best track data for 11,967 tropical cyclones into a single database, called IBTrACS, with information from 1842 to 2012. Included in that database are estimates of wind speeds along the tracks of the storms. This image shows the output of that data. By coloring the maximum sustained wind speed over the course of a storm’s life, certain patterns arise. In contrast to the similar image of storm frequency, the Northwestern Atlantic shows a much greater spread of strong storms, whereas in the Pacific the strongest cyclones seem to group near the Philippines. Credit: NOAA National Environmental Satellite, Data, and Information Service (NESDIS). NOAA Environmental Visualization Laboratory.

   Credit: NOAA SOS

   Coastal communities are increasingly exposed to extreme weather events including categories 3, 4, and 5 hurricanes and storms that generate extreme rainfall events. For example, you need only look at the 2017 hurricane season and consider Hurricane Harvey’s impact on Houston and Hurricane Maria’s impact on Puerto Rico.

2. Location and Landscape

   

   Oblique aerial photographs of Long Branch, New Jersey from before and after Hurricane Sandy. Note how the flood control structures (groins) have shaped the exposure to storm surge and beach erosion.

   Credit: USGS: St. Petersburg Coastal and Marine Science Center

   The physical features of the coastal landscape play a major role in determining exposure. For example, the low-lying coastline of southeastern Louisiana exposes the city of New Orleans and nearby communities to hurricane storm surges from the Gulf of Mexico. Complicating the effects of low elevation features such a narrow bays and inlets that can amplify storm surge. In Module 6 you looked at many case studies of coastal hazards and their impacts, including Super Typhoon Haiyan (Yolanda) that devastated Tacloban City in the Philippines in 2013. Tacloban is another city with a large, dense human population situated close to the ocean on land that sits at a very low elevation. But in addition, Tacloban is in San Pedro Bay. Watch the storm surge simulation of Typhoon Haiyan below to see the effect of magnification of surge height as it enters the confines of the bay.

   Video: Storm surge of Super Typhoon Haiyan making landfall (00:10) No narration.

   This video is a simulation of the approach and impact in Tacloban of the storm surge of Super Typhoon Haiyan. It illustrates how the magnitude of the storm surge increases as it enters a shallow bay such as San Pedro Bay, where Tacloban sits. The result of this unfortunate combination of hazard intensity and location was the loss of 4,000 lives in Tacloban City alone.

   Credit: Maarten van Ormondt. Storm surge of Super Typhoon Haiyan making landfall. YouTube. Nov 10, 2013.

3. Density of People and Property

   Population density on Earth can be explored using this NASA Earth Observatory image. Take a minute to explore this interactive Night Light image from 2016. Consider how this imagery illustrates the distribution of the human population on Earth. It certainly shows the large urban areas well. But one thing to keep in mind is that some locations will show as brighter at night not only due to a greater or denser population, but because of the economics of the area. A wealthier country will have a better and more reliable energy supply.

   We have already considered examples, such as Typhoon Haiyan, and Superstorm Sandy, where very densely populated areas are impacted by severe coastal hazards.

   

   Global population density.

   Credit: United Nations Environment Programme, Global Environmental Alert Service Center for International Earth Science Information Network - CIESIN - Columbia University, and Centro Internacional de Agricultura Tropical - CIAT. 2005. Gridded Population of the World, Version 3 (GPWv3): Population Density Grid, Future Estimates. Palisades, NY: NASA Socioeconomic Data and Applications Center (SEDAC). Accessed August 15, 2023. (Public Domain)

   If this world population map and that of global hurricane intensity shown above are compared, we can see that the Atlantic seaboard of the U.S., as well as the east coast of China, are examples of places with high population density coinciding with high exposure to intense cyclones. Superstorm Sandy was unusual in size and intensity for a late-season storm hitting the northeastern U.S., but based on the map of storm intensity, it was not a complete anomaly. Adding the fact that Sandy, with its incredibly large diameter, impacted so many of the densely populated cities of the eastern seaboard, this was a perfect example of high exposure of people and property. In Module 6, you read about the circumstances of Sandy and the fact that these population centers (including New York, Boston, Philadelphia, ….) are home to 50 million people with an economic output of $3.6 trillion/year. The area definitely has a high exposure to hurricanes as the climate warms.

   

   A nighttime image of Hurricane Sandy, with lights of major cities on the U.S. east coast visible through its swirling clouds, overlaid on top of a map of the U.S. eastern seaboard.

   Credit: NASA: Sandy and OpenStreetMap

Introduction

Sensitivity is the degree to which people and the things they value could be harmed by exposure to a hazard.

Sensitivity to coastal hazards is more difficult to assess than exposure, particularly before a disaster occurs.

In 2011, a 9.0 magnitude earthquake off the Pacific coast of the Japanese island of Tōhoku caused a massive tsunami that killed more than 15,000 people and destroyed or damaged hundreds of thousands of buildings. It also caused a nuclear disaster in the form of meltdowns at three reactors of the Fukushima Daiichi Nuclear Power Plant. However, other nuclear reactors within the path of this event’s tsunami waves were essentially unaffected.

Why did the Fukushima Daiichi plant experience catastrophic meltdowns while other reactors exposed to the tsunami did not? One explanation is that Fukushima Daiichi reactors were more sensitive to tsunamis than other reactors. Sensitivity, as defined earlier in this module, is the degree to which people and the things they value could be harmed by exposure to a hazard. It is important to assess sensitivity to a hazard before an event occurs to more fully understand the potential for adverse impacts. It is also important to assess sensitivity after an event has occurred to locate where the worst effects were felt and to identify lessons that might be applied to future hazard events.

Sensitivity to coastal hazards is more difficult to assess than exposure, particularly before a disaster occurs. Hurricanes and associated storm surge exposure are generally only possible in particular coastal areas globally, and are much more common in some areas than in others. Likewise, tsunamis are generally caused by undersea or volcanic seismic events, which limits the number of places they can physically occur. Because we have much historical experience and physical science knowledge about these hazards, we can often predict with reasonable accuracy which places might be exposed.

Sensitivity, however, is not always as clear. As depicted in the vulnerability scoping diagram presented earlier in this module, one needs to consider both the components of sensitivity to a hazard and measures of that sensitivity. Two components of sensitivity often considered to be important to understanding vulnerability to coastal hazards are infrastructure and demographics. Of these, infrastructure is the more straightforward of the two to assess. Typically, information is readily available on infrastructure’s date of construction, materials used, ability to withstand various hazards, and so on, particularly in developed countries. Understanding the condition and quality of infrastructure enables assessment of its sensitivity to hazards, and consequently the sensitivity of populations that rely on the infrastructure.

Demographic factors such as race, gender, and socioeconomic status can also play an important role in assessing sensitivity to coastal hazards. However, these factors are highly context-specific, and can also interact with one another.

The two aspects of a community most often considered in sensitivity assessments are the demographics of the population and the infrastructure of the built environment. Of these, infrastructure is the more straightforward of the two to assess.

Let’s think of an example we are already familiar with. With Hurricane Katrina, the infrastructure designed to protect the city of New Orleans from storm surges (the levee system) was not strong enough to withstand the surge and therefore failed and the city flooded. Many people living in the city had characteristics that lead to high levels of sensitivity. Poverty, sickness, and old age are three characteristics that were shared by many of the people who suffered the most as a result of Katrina’s flooding. This led to the shocking human catastrophe we witnessed, with thousands of people unable to evacuate and trapped, and some dying for lack of medical help or basic human needs. The city displayed a high level of sensitivity. This became painfully obvious after the storm, but was, perhaps, harder to assess before Katrina happened (although there had been many attempts to draw attention to the issue prior to the storm).

Similarly, but with far less impact on human suffering, with Sandy in New York, the infrastructure of Lower Manhattan, including the subway, was not designed to withstand a storm surge. This became painfully obvious after the storm, too. These lessons in sensitivity are (or should be) what drive communities to improve their resilience to coastal hazards by working to strengthen their adaptive capacity, as we will see in the next section.

Introduction

What can community leaders and all community members do to build their resilience to coastal hazards?

The adaptive capacity of a community is its capacity to cope with, recover from, and adapt to hazard events. Coastal communities around the world are focusing on ways to adapt to increased risk in the face of amplified coastal hazards such as extreme weather and sea level rise.

The term resilience is often used to describe the ability to cope or bounce back after a setback such as a storm surge, or to cope with ongoing challenges such s more frequent tidal flooding. Resilience can be thought of as a measure of a community’s adaptive capacity. As we mentioned before, communities can increase their adaptive capacity and resilience by learning from a disaster or hazard event. New Orleans is certainly a good example that we will examine in a case study.

Our case studies of coastal hazard events around the world throughout this course have highlighted how the issues of social inequity in communities can impact the speed with which and how well certain groups of people are able to recover and bounce back from a setback such as flooding from Katrina or Sandy, or a tsunami such as the devastating 2004 Indian Ocean tsunami. Those things we mentioned in the section on sensitivity that make people more sensitive to the disruption and harm caused by an event such as these – age, health, poverty, and race all can be major obstacles to the ability to bounce back – recover and rebuild homes, lives, and livelihoods after a major setback.

Who are the most vulnerable?

As we have touched on already, there is a strong link between poverty and vulnerability. Why is this? First, the data show that lower-income Americans are more likely to live in neighborhoods prone to chronic flooding and to live in housing that is more susceptible to damage from storms. Second, lower-income people have lower levels of resilience because they do not have the economic cushions that help to reduce the shock when disaster hits. For example, poorer families are less likely to have flood insurance policies and have a harder time finding the resources to rebuild and get back on their feet. This has been clearly shown for families in New Orleans, who even a decade after Katrina were lagging behind wealthier counterparts in economic recovery. Adding to these facts, in many locations, including New Orleans after Katrina and Houston after Harvey, the communities of color were the ones of lower economical means and therefore have more difficulty recovering from the shock of these events. Longer-term effects of flooding also include health impacts and again, lower-income people and people of color tend to struggle more due to lack of access to high-quality healthcare in some cases. For example, after Katrina, houses that may not have been very badly flooded were rendered unlivable due to the black mold that grew in the hot, humid climate. It is much harder for a poor family to address more insidious long-lasting impacts such as these, and they can lead to chronic health issues such as high levels of childhood asthma.

As we work through the remaining modules of the course, keep in mind the need to find equitable solutions to the issues we are examining. If we, as a society, cannot address the need to increase resilience for everyone, the future is going to be very challenging for many people[d1].

[d1]Reference:

Hurricanes hit the poor the hardest

To help you understand Exposure, Sensitivity, and Adaptive Capacity, you will be introduced to several case studies.

Reflecting on Coastal Community Vulnerability

Overview

In this module, you learned about the components of vulnerability as defined by coastal policy experts. You read many case studies that helped to illustrate the components of vulnerability: exposure, sensitivity, and adaptive capacity.

For the Module 11 lab, we will spend time reflecting on what makes one coastal community more vulnerable than another and how they might reduce their vulnerability to coastal hazards. You will read the following statement and respond appropriately based on your knowledge of module concepts. You will respond to at least one other student's response throughout the week.

Discussion Prompt

Using one or two of the case studies from Module 11 (and listed in Required Resources), in this discussion, consider how adaptive capacity may be increased to reduce the vulnerability of a coastal community. Be specific in terms of location and coastal hazard.

Instructions

1. Use Word or another text editor to respond to the prompt with your thoughts backed up with evidence from the Module 11 case studies. The length of your response should be about 200 to 400 words. (Typing your response in Word or another text editor and then copying/pasting from Word or similar to the discussion forum is recommended to avoid losing your work midstream in the event of an accidental browser closing, intermittent Internet connectivity, etc.)
2. Go to Module 11 Lab (Discussion) and type or copy/paste your response to the prompt into the text box marked 'reply' and select Post Reply by 11:59 p.m. on Thursday to allow time for responses. Your response is now visible to your classmates and your instructor.
3. Read through others’ responses and write a thoughtful reply to at least one other student by 11:59 p.m. on Sunday. These replies should be either a rebuttal in which you add your ideas in the form of a persuasive argument (written with respect for the originating author), or a response that agrees with, supports, and builds upon the original response. Because a timely response to the conversation is part of your grade, subscribing to the forum is required. Check in to the discussion forum often throughout the week to post and respond to comments.

Grading

The grading rubric will help you understand what constitutes an appropriate level of participation on your part. The instructor reserves the right to not award any credit (including points for timing and interaction) if the content of the posts, however on-time they may be, are off-topic, offensive, or otherwise inappropriate. Such posts may be deleted at any time by the instructor as well.

We have introduced the three dimensions of vulnerability – exposure, sensitivity, and adaptive capacity – with a focus on coastal disaster contexts. In addition to showing how to quantify these dimensions of vulnerability, we have also shown how this model of vulnerability can be used to assess and compare the physical and social vulnerabilities of different coastal settings and populations. In the activity at the end of this module, you explored how the vulnerability model can be used to compare the vulnerability of three coastal communities to hurricanes. The case studies were meant to help you think about sensitivity as a component of vulnerability. Sensitivity can be related to physical factors, such as age and quality of infrastructure, as in the Fukushima Daiichi nuclear power plant and Florida mobile home examples, or it can be related to social factors, as in the Indian Ocean tsunami example. Although lessons from each of these examples are generalizable in the broad sense, it is important to think about vulnerability, including sensitivity, in a place-specific, localized manner. For example, issues related to mobile home sensitivity to hurricanes, although relevant in many parts of Florida, are not relevant to all places exposed to hurricanes. Likewise, many countries that are exposed to tsunami hazards either do not use nuclear energy or do not have any plants in tsunami hazard zones. In these places, the lessons of the Fukushima Daiichi disaster are only applicable in the generalized sense, i.e., that seawalls should be high enough to protect key resources from the highest waves likely to occur based on current science, and that critical resources requiring electrical power incorporate redundancy.

In the following modules, we will apply the concept of vulnerability to three kinds of coastal hazards: tsunamis, hurricanes, and sea level rise. We will also discuss policies in relation to those hazards. While tsunamis and hurricane hazards are short-term hazards that exist a few hours to several days, sea level rise is a medium- to long-term hazard that shows its impacts slowly over decades. We will discuss tsunamis and hurricane hazards, the two short-term hazards in the next module, and discuss sea level rise, the medium- to long-term hazard, in the following module.

Reminder - Complete all of the Module 11 tasks!

You have reached the end of Module 11! Double-check the to-do list in the Module 11 Roadmap to make sure you have completed all of the activities listed there before you begin Module 12.

Students will assess how government and stakeholders can plan for and respond to coastal hazards.

Learning Objectives

By the end of this module, students should be able to:

• examine the stages of the disaster management cycle and its application;
• identify and compare policy options for preparing for and responding to immediate coastal hazards;
• critically assess the implementation of the emergency management cycle in real disaster case studies.

Module 12 Roadmap

Questions?

If you have any questions, please use the Canvas email tool to contact the instructor.

Let’s go over some emergency management terminology to begin.

Policy

A policy is a principle or set of principles that guides decisions and tries to produce sensible, positive outcomes or to avoid the negative effects of some behaviors. A policy can apply to governments, businesses, other groups (such as sports teams or college courses), and even individuals. Policies are often established by governing bodies and implemented by executive officers. Many levels of government, schools, etc., have recently developed policies to help guide people through the COVID-19 pandemic.

Policies can only suggest ways for people or groups to do the right things or to avoid doing the wrong things, while rules or laws can use punishment as enforcement. We have all become familiar with the heated debates about mask-wearing during the pandemic. These arguments underline the difference between policy and rule of law.

So, tsunami and hurricane storm surge policies aim to help the public avoid or minimize harm from these natural hazards and recover quickly and efficiently from them when they strike.

Natural Hazards

Natural hazards are geophysical events that pose threats to human life or health, to the natural or built environment on which people rely for life support, and to things that people value, such as economic wealth or material possessions. Natural hazards are potentialities; that is, they have not yet happened but could occur at some time in the future.

Disasters

When a natural hazard such as a tsunami or hurricane does become active, it can trigger a disaster. Natural disasters are the major adverse human events resulting from natural hazards. Disasters are typically associated with loss of life, impaired human health, destruction of the natural and built environment, financial damage, and loss of land and possessions. The severity of the disaster is a function of the magnitude of the geophysical event coupled with the vulnerability of the people and place, which was the topic of Module 11.

Emergency Management Cycle

The emergency management cycle is used to understand appropriate human preparation for, and response to, disasters, including those resulting from a coastal hazard. The emergency management cycle can be divided into four stages: mitigation, preparedness, response, and recovery.

Mitigation

Mitigation includes all efforts that a person, household, community, or any other social unit takes to make a disaster less likely to happen or to reduce the negative effects if a natural hazard were to occur. Mitigation activities occur well before a natural hazard strikes and can be structural, such as building a  seawall, or non-structural, such as developing a warning system.

Preparedness

Preparedness, in contrast to mitigation, can take place right before the natural hazard strikes. Its goal is to make sure that the individual or community knows which tools to possess and how to use those tools, what actions to undertake. The actions can also continue during the hazardous event, or immediately after disaster strikes. In preparing for a hurricane, for instance, important preparedness activities may include planning for evacuation, including knowing when to evacuate, which destination to evacuate to, and what evacuation route to take.

Response

Response is the emergency assistance that takes place during or immediately after a disaster. Its purpose is to save lives, treat injuries, and reduce property damage while meeting the most fundamental needs — water, food, shelter, and medical aid — of the people affected by the event. The response period is stressful both to emergency managers, who face limited time, information, and resources, and to the public, who face evacuation, family separation, and the loss of property and loved ones.

Recovery

Recovery is the stage during which individuals, families, communities, and governments repair and reconstruct what has been damaged by or lost in the disaster. At the same time, recovery presents an opportunity to reduce the risk of a similar catastrophe in the future – in other words, to start mitigation activities and thereby start the emergency management cycle again.

In reaction to the disaster, governments usually provide substantial resources for recovery, including economic recovery, housing recovery, and individual, family, and social recovery, and possible mitigation of potential future natural hazard events. In addition, funds and assistance come from many other sources, including non-profit organizations, faith-based organizations, and volunteers.

Introduction

Mitigation involves taking action to reduce risk. Mitigation is a long-term planning activity, unlike preparedness, response, and recovery, which are more immediately part of the emergency itself. But mitigation can begin following a disaster, during recovery, to mitigate the effects of any future disaster. In the mitigation phase of the emergency management cycle, activities aimed at decreasing the likelihood of disaster or reducing its negative impacts can either be structural or non-structural. Examples of structural mitigation activities include building physical infrastructure such as sea walls or retrofitting existing buildings to withstand the hazard, or to serve as shelters. Instances of non-structural mitigation activities include developing storm surge warning systems, post-disaster recovery plans, and educational programs. Other non-structural mitigation measures include flood insurance programs (although some consider this as part of preparedness), and land use planning activities like zoning. As you can see, mitigation activities are wide-ranging and can overlap with other phases of the emergency management cycle.

Learning Check Point

Please take a few minutes to think about what you just learned and answer the question below.

The goal of the preparedness stage of the disaster management cycle is to enhance people's capacity to respond to natural hazards and recover from a disaster. The basis of preparedness is planning, whether that planning takes place at the household, local, state, national, or international level. Thus, policies from a local to international scale that guide sound hazard and disaster planning are essential. Emergency planning and communication of plans for their successful execution when a hazard occurs, happens at many levels of society, from the federal level down to the individual. Therefore, for organizational units including state, county, and city governments, to schools, universities, hospitals, and many other organizations, a clear plan is essential.