Cost-benefit Analysis: Quantitative or Qualitative?

Some of these costs and benefits can be assessed quantitatively in terms of dollars spent, saved, or earned. Construction, maintenance, and operation costs can be estimated and compared for different strategies: for example, the costs of continuing to replenish and maintain a sandy beach versus the cost of replacing it with a sea wall (including the cost of maintaining the sea wall and operating any gates or other features). Economic costs and benefits– including jobs created to build or maintain new infrastructure; impacts on major local industries such as shipping, fishing, or tourism; and effects on property values – can also be modeled, quantified, and compared.

However, other types of costs and benefits may not be easily assessed in dollar terms. Rather than use quantitative analysis, these benefits, and costs should be assessed qualitatively using a subjective scoring system. The first example in this section – reducing vulnerability by managing retreat or beach nourishment/restoration – is assumed to be quantifiable in terms of dollars saved. This may be true for the exposure component of vulnerability, which can be quantified in terms of changes in the number and value of homes and businesses exposed to sea level rise-enhanced flooding. However, it is much more difficult to assign a dollar value to changes in the social dimensions of vulnerability, such as the reductions to residents’ adaptive capacity that may occur if managed retreat from a coastal neighborhood disrupts social networks. Instead of assigning a dollar value to the residents’ adaptive capacity, stakeholders in a participatory planning exercise can assign subjective scores, perhaps by rating the costs and benefits for residents’ adaptive capacity on a scale of 1 to 10 for each policy option. Average cost and benefit scores are compared to determine which option would be most beneficial (or least costly) for adaptive capacity. These subjective cost-benefit scores can then be reweighted (multiplied by a constant value) so that they can be compared and combined with scores for other types of costs and benefits, including those assessed in dollar terms.

Like social vulnerability, environmental and design/livability costs and benefits can be challenging to quantify. For environmental costs and benefits, it may be possible to assign a dollar value using an ecosystem services model, which prices the cost or benefit of a change to environmental functions in terms of its value to society. For example, the environmental benefits of a strategy that maintains or increases the extent of coastal wetlands could be quantified in terms of the wetland’s increased ability both to protect coastal property from storm surge and to provide habitat for commercially valuable fish.

South Florida’s mangrove wetlands provide several benefits to coastal residents. Some of these benefits – such as their ability to protect property from storm surge – may be quantifiable using an ecosystems services model. However, some benefits these wetlands provide – such as habitat for endangered species and natural beauty – may be best assessed qualitatively.

Credit: Mangrove Plants Swamp in Florida: Public Domain, Bill Wilen, U.S. Fish and Wildlife Service, downloaded from Wikipedia

In Module 9 we looked at an example of cost-benefit analysis for managed realignment in the United Kingdom and considered the benefits of ecological services provided by coastal marshes, and how they add to the benefits of managed realignment projects.

However, this increase in wetlands could provide other benefits – such as habitat for an endangered species – that are more difficult to quantify. Similarly, impacts of a strategy on community design/livability – such as making a community more attractive and walkable or providing better access to amenities such as grocery stores or public transportation – could be quantified in terms of changes in public health and transportation costs, but aesthetic considerations would remain highly subjective and are better assessed qualitatively.

Costs and benefits associated with equity and compatibility with local plans and goals may be the most difficult to quantify. Equity considers who will pay and who will benefit from implementing a given strategy. For example, although a cost-benefit analysis may show that the benefits of a particular strategy far outweigh the costs, equity considerations may reveal that wealthy landowners or corporations will receive most of the benefits, while the most vulnerable and disadvantaged stakeholders will bear most of the costs. In this situation, stakeholders may decide that the large decreases in equity associated with implementing such a strategy outweigh its other benefits.

As we saw with the example of Toms River, NJ, strategies for preparing for sea level rise can be seen as an obstacle to existing plans or goals – such as attracting new businesses, maintaining tourism, or increasing the stock of affordable housing, and can complicate cost-benefit analysis. If stakeholders oppose a strategy due to these conflicts, the strategy could be ranked higher in the cost column than if there were no conflicts of this kind.

Computer models are an essential tool for studying costs and benefits. Physical models of the ocean and shoreline can be used to study how protective structures such as sea walls and levees can reshape the coastline by changing currents, waves, and erosion. From the outputs of these models, scientists can calculate costs and benefits in terms of losses or gains in coastal property, in amenities such as beaches, or in habitat. Economic or demographic models can then be used to study how these changes in coastal processes, landforms, and ecosystems may interact with the local economy or population trends, potentially resulting in additional costs or benefits (such as increasing poverty or growing the tax base). Urban planning and design models can assess the effects of these changes in the physical and social environment on urban spaces, including changes in traffic patterns on city streets or in sight lines (views) from scenic coastal hotels or parks.

As these examples suggest, human and environmental systems in the coastal zone are closely coupled: human actions reshape the natural environment, and changes in the natural environment reshape human communities and infrastructure. Therefore, to understand the costs or benefits of a proposed strategy for preparing for sea level rise and related hazards, scientists and decision-makers should consider these complex, reciprocal interactions between human and environmental processes. Because computer models are able to capture these complex interactions, they are often one of the best tools for understanding the costs and benefits that these interactions may cause. Models may be particularly useful when attempting to understand whether combining two or more sea level rise strategies will change the human-environment system in ways that lead to unexpected costs or synergistic benefits. The next section considers some of the possible benefits of combining strategies. Fittingly, coming near the end of the course, this is one of the most advanced views of the Earth System we have had this semester.

The above discussion shows how cost-benefit analysis can be used to compare individual strategies for preparing for sea level rise and related coastal hazards. However, the most cost-effective option is often not a single strategy, but a combination of synergistic strategies. For example, when used alone, breakwaters or artificial reefs can be used to slow coastal erosion, but are not effective at preventing flooding due to sea level rise and storm surge. However, these strategies can be combined with other complementary strategies – such as levees or beach/dune reconstruction – that can mitigate sea level rise and storm surge flooding but are not as good at slowing coastal erosion. Combining strategies can also be an effective way to meet multiple design goals. For example, including a waterfront park in a plan for managed retreat can reduce the exposure of coastal infrastructure to flooding while also fulfilling other goals, such as creating new space for recreation and environmental restoration.

Learning Check Point

This exercise is not for credit, but you are required to understand this material for the formal assessments in this module.

Stakeholders in Ventura, California have chosen to combine several strategies for reducing erosion at Surfer’s Point.

Re-visit this NOAA article, which was also presented in Module 9, Restoring Surfer's Point, then answer the following questions:

In addition to the benefits of implementing complementary strategies in one place, communities should also recognize that the types of strategies that are most beneficial will vary from place to place across the community’s jurisdiction – strategies that are highly beneficial in one area of the community may not be as beneficial in another, and may even be harmful. Thus, communities should consider adopting not only multiple complementary strategies in one area, but also different sets of complementary strategies for different areas. The next section discusses how communities, governments, and stakeholders can use geographic information systems to better understand how differences in the social and physical landscape across their jurisdiction may affect the suitability of these strategies from place to place.

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

For now, New York City has chosen to adopt protections similar to those outlined in the hybrid strategy. Why would the City choose a strategy that is beneficial now, but may not be cost-effective in the future? One reason may be that people often give more weight to present-day costs and benefits than to future costs and benefits. Recognizing this difference between present value and future value, economists have developed a technique called discounting that decreases the value of future costs and benefits at a constant rate. This means that costs or benefits that will not occur for many decades are given much less weight in the cost-benefit analysis than costs or benefits that will occur in the next few days, weeks, or years. When discounting is applied, the rationale for New York City’s decision is clearer. Building a sea wall now would be very costly, requiring large expenditures in the short-term. While the benefits of building the sea wall could be large in the long-term, these benefits will not be realized for some time, and are therefore offset by the significant upfront costs.

As this New York City example illustrates, it can often be advantageous for communities to switch from one strategy to another as costs and benefits change. An adaptive management approach to preparing for sea level rise can help communities to identify opportunities to adopt new strategies or to adjust strategies already in place as conditions and goals change. In the adaptive management cycle, stakeholders and experts work together to monitor the effects of implementing coastal protection strategies on natural and human systems. Based on this monitoring, they learn which strategies are furthering or frustrating design goals (such as protecting neighborhoods from flooding or restoring coastal habitat) and share this learning with policymakers by suggesting changes or adjustments in strategies.

In the context of climate-change related hazards such as sea level rise, adaptive management is often supplemented with flexible adaptation pathways: plans that show how existing strategies for adapting to sea level rise can be supplemented, adjusted, or replaced with other strategies in the future as conditions change. By building flexibility into the planning process to allow easy transition from one strategic pathway to another, these pathways can help communities adopt the most cost effective strategies now, while keep their options open for the future.

Learning Check Point

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

Of the major U.S. cities that face the greatest uncertainty related to sea level rise, Miami may be the poster child. The greater Miami area of south Florida faces higher than average sea level rise rates due to its location on the Atlantic seaboard (see Module 4). This, along with its low-lying topography and its porous limestone geology, all conspire to create a very uncertain future for the metropolitan area of more than 6 million. Examination of any maps of projected sea level rise in south Florida should set alarms ringing for the viewer. Take a look at this animation of sea level rise based on data from the Green Policy 360.

An animation shows the effects of rising sea level on the land area of the Florida Peninsula.

Credit: Green Policy 360

Part of the metro region, Miami Beach is a city of 91,700 people situated on a barrier island connected to the mainland and the city of Miami by bridges. Most people associate Miami Beach with glitzy wealth, beautiful Atlantic beaches, and a tropical climate. They may not be aware of the challenges associated with the rising seas coupled with the geography and geology of the area.

The geology of this part of Florida makes it especially susceptible to sea level rise related issues. The Florida peninsula is composed of a limestone platform, and the barrier shoreline that Miami Beach occupies sits upon this platform. In addition, the Florida peninsula is low in elevation and Miami Beach has a maximum elevation of only a little over 1.5 m. The lowest elevations are on the bay side of Miami Beach. This is the area discussed in the video “Is Miami Doomed?”. You can explore the effects of sea level rise on Miami Beach at the NOAA Sea Level Rise Viewer, which allow you to search for a location and manipulate projected sea levels and visualize the effects on the chosen location.

In addition, the geology presents other challenges: the oolite limestone platform is highly porous, so seawater can infiltrate beneath the ground and come up from below during high tides. Furthermore, the design of the older drainage systems that rely on gravity flow to the ocean has resulted in seawater backing up onto roadways during high tides. This adds to the effects of “sunny day flooding” which Miami is becoming accustomed to. The porous nature of the limestone geology also precludes using methods like levees and dikes to hold back rising seas, as the water just migrates under any structures put in its way.

Let’s consider some of the reasons behind the sunny day flooding and king tides that are disrupting the utopic life there. First, of course, is sea level rise. We learned in Module 4 that parts of the east coast of the U.S. are suffering from greater rates of sea level rise than most places. And Miami is one of these locations. Research has shown that in addition to eustatic sea level rise, there is a combination of other factors contributing to sea level rise along the southeastern coast of the U.S. In addition, there are king tides, which occur seasonally, during the fall and early winter. King tides are a natural phenomenon determined by the predictable movements of the Earth, Moon, and Sun, but exacerbated by local weather patterns and regional ocean conditions. King tides occur when the Earth, Moon, and Sun are aligned at perigee (Moon is closest to the Earth) and perihelion (Earth is close to the Sun). These conditions result in the largest tidal range seen over the course of a year. These factors, combined with a unique set of regional geological characteristics, and high exposure to tropical cyclone storm surges, make south Florida a highly sea-level challenged part of the U.S.

How sustainable is the economic powerhouse of Miami Beach? What future lies ahead, and for how long can business as usual be maintained? What adaptation plans are being made?

The flooding experienced today in Miami is just the beginning, given the sea level rise projections we have already discussed. In the 2016 Atlantic video, Is Miami Doomed? The mayor and city manager of Miami Beach both sound optimistic and are pushing forward with innovative ideas for adaptation, such as the installation of pumps, raising road levels, etc. The drainage systems are being redesigned with pumps to return the water to the ocean.

But this video avoids some difficult questions about the complexity, costs, and sustainability of these approaches. To begin, there is the question of scale. It seems foolish to think that the whole of the city of Miami Beach can be raised in elevation, not to mention the rest of the city of Miami. Many other authors and experts have raised important questions about how long reliance on pumping water out into Biscayne Bay and other current approaches can last as sea levels rise. The larger policy questions of how to maintain the infrastructure such as sewage and drinking water, etc., and provide an equitable quality of life for all citizens in the future loom over Miami.

The Maldive Islands in the Indian Ocean and other low-lying island nations such as the Marshall Islands and others in the Pacific Ocean all face extreme sea level rise risk and are addressing the problem in a variety of ways. The Maldives, the Marshall Islands, and several other island nations are made up of numerous coral atolls, each including several islands of varying sizes. All the islands are very low profile, with elevations usually of no more than two meters. They are currently facing multiple sustainability issues due to sea level rise, with some residents seeing only a future of migration away from their island homes.

The simple issue of frequent tidal flooding and accompanying shoreline erosion and loss of livable land area is compounded by the more complex problems related to salt water intrusion into the freshwater lenses that the islanders depend upon for their drinking water. Chapter 8 of Jeff Goodell’s book, “The Water Will Come” discusses in detail the issues of the Marshall Islands. He says of the groundwater supply: “The problem is, as seas rise, the salt water pushes up from below, leaving less and less room for freshwater (which, being more buoyant, rides on top of the salt water). In addition, as the seas rise, flooding from storm surges is likely to become more common. When an atoll is inundated, the salt water can seep into the freshwater lens, contaminating it. It can take years before it is suitable for drinking again." (Goodell, 2017).

Meanwhile, the Maldive Islands, which comprise 1,200 islands on 26 atolls, face similar challenges. In fact, the capital of the Maldives, Malé, sits on the most densely populated island in the world. As the image below illustrates, the whole island is completely developed. Drinking water is desalinated by reverse osmosis using brackish groundwater, which is pumped from 50-60 meter wells. Malé is the center of all commercial activities of the Maldives. The main industry of the Maldives is tourism, comprising 28% of the nation’s GDP. According to the United Nations Development Programme (UNDP) “Given that these reefs support both the country’s tourism and fisheries industries upon which the people depend almost exclusively, climate change is a profound threat to its very economic base.”

Understandably, the government leaders of these island nations have a great interest in how the world is addressing climate change, since they are on the front line in the sea level rise battle, with everything to lose, while contributing very little to the global anthropogenic causes of climate change. One approach of the presidents and prime ministers of these island nations has been to work hard to get the attention of the rest of the world and push for policies that reduce greenhouse gas emissions. This has had limited success and caused plenty of frustration. Meanwhile, adaptation policy options are limited. The islands are small and low in elevation, while economic opportunities for residents are limited and affected by climate change. Therefore, migration is often the best adaptation option. A United Nations report analyzed the migration patterns and modeled migration and population projections to 2055 for several Pacific Island nations. The study found that for Tuvalu, which has a current population of a little less than 11,000 people, 70% of households surveyed felt that migration would be necessary if sea level rise impacts worsened and that 15% of the population had migrated internationally between 2005 and 2015. The Modeling indicated that the migration rate (both internally and internationally) will roughly double by 2055. The reasons for migration included climate change-related impacts but also economic needs, which can be related as climate change affects agriculture and fisheries. So, from this information, we can see that sea level rise is one of a complex of related stressors for the people of island nations like Tuvalu.

Reference: United Nations Economic and Social Commission for Asia and the Pacific Climate Change and Migration in the Pacific: Links, attitudes, and future scenarios in Nauru, Tuvalu, and Kiribati.

International Politics of Sea Level Rise – The Maldives and Kiribati

The New Scientist article, On front line of climate change as Maldives fights rising seas, discusses recent developments in the efforts in the Maldives to plan for the future. The current president of the Maldives is pushing for rapid land reclamation using sediment dredged from existing atolls and pumped to create new islands as sea levels rise. To fund this expensive method of land reclamation, the Maldives government is negotiating a lucrative deal with the Saudi government to lease the Faafal Atoll for shipping security purposes and tourism. While proponents tout this method as a simple solution that will avoid migration away from the Maldives, there are many resulting conflicts. Thousands of residents would actually be displaced to other islands as a result of this dredging project, raising societal concerns. Also, the deposition of sediment onto coral reefs smothers and damages the reefs themselves.

Meanwhile, in Kiribati, a similar scenario is playing out. As reported in the Guardian: Kiribati’s president’s plans to raise islands in the fight against sea-level rise, the newly elected president of Kiribati is focusing heavily on increasing island elevation using dredging and construction of causeways to connect islands. There are international politics and security questions being raised about these plans, including concerns from the U.S. that China may have strategic and military interests in the region and the U.S. naval base in Hawaii is only 2,000 km (1,243 miles away). This complex issue is developing, so stay aware.

These examples reveal the extreme lengths to which the low-lying island nations of the world must go if they are to survive a future of rising sea levels. The structural mitigation measures discussed above may also need to be considered a short-term solution to prolong the sustainability of communities on these islands. Depending on the future rates of sea level rise, conditions may prove untenable in the 22nd century or before, if ways to sustain essentials such as freshwater supplies for human consumption and agriculture cannot be maintained.

Natural Regeneration of Reef Islands

The National Geographic article, Will Pacific Island Nations Disappear as Seas Rise? Maybe Not provides a very clear description of the situation for the island nations, with the prime minister of the island nation of Tuvalu pleading his case to the United Nations for a nation in danger of disappearing due to sea level rise. The article details an interesting contribution to the conversation about the future of coral atoll islands from coastal geomorphologist Paul Kench, of the University of Auckland's School of Environment, and colleagues in Australia and Fiji, who have been studying how coral atoll islands respond to sea level rise. Their research suggests that, left in their natural state, coral atolls can grow in elevation and keep pace with sea level rise, when left unaltered by human activity. They have measured this growth and reported that only 20% of the islands studied decreased in size during the time period considered. The islands that are heavily populated and altered by human infrastructure, not surprisingly, are the ones deemed unsustainable in terms of ability to naturally keep up with environmental changes, while sparsely populated, less developed islands can more easily keep up with the pace of sea level rise with natural processes.

Learning Check Point

Regarding research conducted by Paul Kench and other researchers, the article states: “They found that reef islands change shape and move around in response to shifting sediments, and that many of them are growing in size, not shrinking, as sea level inches upward”. And “Their analysis, which now extends to more than 600 coral reef islands in the Pacific and Indian Oceans, indicates that about 80 percent of the islands have remained stable or increased in size (roughly 40 percent in each category)”.

New York City has a high level of exposure to sea level rise due to its coastal location on the Hudson estuary and its barrier shoreline on the Atlantic Ocean, but its status as the most densely populated city in the U.S. makes it particularly vulnerable in comparison to other coastal cities with similar geographies. Hurricane Sandy shut down New York, cut power for days or weeks to hundreds of thousands of people, flooded homes and businesses in Manhattan, Staten Island, Queens, and many other areas, and caused $19 billion in damages and economic losses and at least 44 deaths of city residents. The New York Stock Exchange closed for two days, sending economic shockwaves worldwide. The Subway and all of the road tunnels connecting Manhattan island to the mainland were flooded and disabled. One thing Sandy also achieved was to focus public attention on the vulnerability to storm surges and sea level rise of the economic center of the U.S. In the years since Hurricane Sandy in 2012, a great deal of work has been done to address New York’s vulnerability to flooding from storm surge and sea level rise. There have been multiple proposals, plans, and strategies considered for increasing New York’s climate change resilience through adaptation.

Some of the major concerns that are being addressed in the planning process are:

• As sea levels rise the number of people living within 100-year (1% annual chance of flooding) flood zone areas will increase significantly. The number is estimated at 20 million by 2050. This will necessitate many more property buyouts such as those that took place after Hurricane Sandy.
• Water treatment plants (an estimated 40%) will be compromised by flooding, increasing the risk of contamination.
• Power plants (an estimated 60%) will need to be relocated, flood proofed, or elevated to avoid flooding, which would threaten the city’s power supply, especially during high water times.
• Transportation systems will need to be upgraded to avoid regular flooding. This includes highways, airports, bridges, tunnels, subways, and railroads.

Other areas of essential infrastructures, such as the Meadowlands in New Jersey, will flood. This area of warehouses, railroad yards, and other important commercial infrastructure is slated for conversion to a national park in the future.

Plans for addressing the increasing threats of flooding include:

• Designs for large barrier systems to protect the city by blocking the storm surges and from the Atlantic Ocean from entering New York Harbor;
• Designs for rethinking the land use of Manhattan and surrounding boroughs, returning some areas to green space.
• Increased number of property buyout projects. During the recovery period following Sandy New York state encouraged homeowners who qualified to participate in a property buy-out program, an example of managed retreat, as described in Module 9. Hundreds of homeowners, including those in Staten Island communities, chose to do so and move to safer locations and the neighborhoods where their houses once stood have been returned to nature, providing tidal flooding buffer zones.

Visit New York’s Fourth Regional Plan to read more details about how this planning process is playing out. This page addresses protecting coastal communities from storms and flooding. An important aspect included in the page linked here is ensuring that the planning process is equitable for all members of the communities it affects. The physical exposure and social exposure maps illustrate where socially at-risk communities are located in relation to the physical exposure to flooding. This consideration was discussed in Module 11 and will also be the focus of Module 13 lab. So where does New York City stand in terms of sea level rise adaptation policy after years of planning? All of the plans are at some stage in the process of becoming reality, but in many cases, they have not yet moved into implementation as the projects involve years of design and community input and are extremely expensive so full funding is hard to achieve. As outlined in the MIT Technology Review article The "mind-boggling" task of protecting New York City from rising seas, although New York is ahead of most coastal cities in climate change adaptation planning, none of the big ideas that were funded by the federal government as a result of the Rebuild by Design competition for Manhattan have actually begun construction, but we will see construction soon.

For residents of Manhattan, the focus has been on the plans to create a 10-mile perimeter of multi-use waterfront space around Lower Manhattan that includes a combination of flood protection and green space that can absorb flood waters when inundation occurs. This project began with the Rebuild by Design Competition where design companies were invited to submit proposals for flood resiliency plans for lower Manhattan. Proposals were chosen and teams formed to create the designs. The design firm Bjarke Ingels won the contract to develop the design and the proposed project became known as the “Big U”. Years of planning, design work, and community stakeholder input through facilitated workshops took place and the completed plan was presented to the city. As the video linked below outlines the city is now beginning the implementation of the plan, but with major changes, with which some of those involved in the complex planning process are not entirely happy. The video explains the steps and shows maps of the designs, which include a fringe green space around the lower part of the city, with elevated berms to hold back the water as well as lower elevations designed to flood at times of high water. Stakeholder input ensured that the needs of all sectors of the community were met. An emphasis was placed on public access so that the whole project provided recreational opportunities for city residents and visitors.

Video: The Big U | Going In With Brian Vines (9:52)

The video provides a good example of how adaptation planning with stakeholder participation works. The New York City government made some executive decisions after the planning process was completed that changed the plans significantly. The changes removed some of the components involving allowing flooding of park areas in times of high water, preferring elevated berms over intentional lower elevations and natural habitats. It will be interesting to see how the plans are finally implemented, how the public feels about the results, and how the project as a whole and its component parts perform when high water affects lower Manhattan, as a result of a storm surge or the inevitable higher tides in the upcoming years.