Coastal communities face hazards from coastal storms and flooding that can cause loss of life, property damage, and damage to the environment. More specifically, coastal communities face threats from erosion and damages from waves, wind, and storm surges. For example, during Superstorm Sandy in 2012, shoreline water levels rose across the East Coast, causing billions of dollars in property damage to homes and businesses. These threats can be exacerbated by several factors, including sea level rise and commercial and residential development, according to Corps documents on coastal risk reduction and resilience. For example, rising sea levels increase the risks from regular tidal flooding and coastal storms and new construction along coastlines can increase the number of people and buildings at risk from the storms. The Corps constructs projects to help reduce the risks from coastal storm hazards and mitigate erosion, wave damage, and flooding, which may include the use of hard structures. The Corps has decades of experience developing projects that use hard structures, such as revetments, seawalls, and storm surge barriers, to reduce the risks from coastal storm hazards, according to a 2014 report by the National Academy of Sciences (see fig. 1). Natural infrastructure can also be designed and developed for coastal storm and flood risk reduction purposes. Natural infrastructure can involve several types of natural features that have the potential to reduce risks to coastal areas from storms (see fig. 2). Diverse natural features occur in different areas of the United States. For example, some areas along the Florida Gulf Coast are host to mangroves—coastal wetlands found in tropical and subtropical regions—that can reduce the impacts of high energy waves from storm surges. The extent to which natural infrastructure can reduce risks to coastal areas from storms and flooding depends on the types of natural features being used. For example, underwater vegetation, such as seagrass, has less capacity to reduce wave energy than a coral reef, which is a hard underwater structure, according to scientific studies. According to a 2014 National Academy of Sciences report, in addition to reducing the risks of storms and flooding for coastal communities, projects using natural infrastructure may provide other benefits, depending on the type of natural feature associated with the project. Among other things, natural infrastructure has the potential to enhance commercial and recreational fisheries and create recreational opportunities. For example, natural infrastructure may support fish habitats, which could enhance a commercial or recreational fishery. In addition, wetlands may improve habitats for birds, which could enhance bird watching activities. Similarly, replenishing beaches may provide more beach area for individuals to use for recreational activities, and provide nesting habitat for birds and sea turtles. The Corps’ Civil Works program—responsible for water resources projects—is organized in three tiers: a national headquarters in Washington, D.C.; eight regional divisions; and 38 districts (see fig. 3). Corps headquarters primarily develops the policies and guidance that the agency’s divisions and districts carry out as part of their oversight responsibilities for the water resources projects under the Corps’ purview. Corps districts are responsible for planning, engineering, constructing, and managing water resources projects in their districts, including projects that consider or use natural infrastructure. The Corps has several programs and initiatives related to using natural infrastructure for water resources projects. For example, the Engineer Research and Development Center, the research organization within the Corps, manages a portfolio of research related to water resources projects that includes research focused on flood risk management and coastal systems. The Corps also has an initiative called Engineering With Nature®, which the Corps’ scientists and engineers developed to facilitate using sustainable practices in Corps projects. The Corps develops water resources projects, including coastal storm and flood risk management projects, in conjunction with nonfederal sponsors, such as state and local governments. According to Corps guidance, the planning process for these projects begins with a nonfederal sponsor identifying a problem and approaching the Corps to help develop a solution. Upon statutory authorization for a study and appropriations to fund it, the Corps and the nonfederal sponsor enter into an agreement to conduct a feasibility study for a potential project. Nonfederal sponsors are to participate in the planning process, as well as remain involved through project design, construction, and post-project operations and maintenance. For example, for projects where the Corps constructs hard infrastructure, such as a seawall, the nonfederal sponsor is to assume responsibility for monitoring and maintenance costs associated with the seawall after its construction. In contrast, for a project that involves replenishing a beach, the Corps and the nonfederal sponsor usually share the cost of replenishment for a specific period of time, typically 50 years. The U.S. Water Resources Council’s 1983 Economic and Environmental Principles and Guidelines for Water and Related Land Resources Implementation Studies (Principles and Guidelines) outline the standards and procedures that the Corps is to follow for planning water resources projects, including those with coastal storm and flood risk management objectives. The Principles and Guidelines establish that the federal objective of water resources projects is to contribute to national economic development while protecting the nation’s environment. The Corps implements the planning process outlined in the Principles and Guidelines by conducting feasibility studies for proposed water resources projects. The Corps’ Planning Guidance Notebook (Planning Guidance) provides detailed guidance on how to implement the general process outlined in the Principles and Guidelines for planning water resource projects. The Corps’ feasibility study process includes four major phases and five milestones, as shown in figure 4. The Corps initiates a feasibility study by forming a project team, comprising Corps engineers, economists, planners, and other specialists, to conduct the study. The Corps project team begins with a scoping phase that specifies the problem, such as the potential for coastal storm and flood damage, and identifies opportunities for a project to address the problem. The project team then inventories conditions in the project area, including physical, economic, and social conditions, and forecasts how these conditions may change over the life of a potential project. As it continues the scoping phase, the project team identifies various measures that could address the problem, such as replenishing an existing beach or constructing a seawall. The project team then develops potential individual measures or combinations of measures (e.g., beach replenishment and seawall construction) into an initial list of alternatives. Since 2016, the Corps has been required by statute to consider natural infrastructure in certain circumstances. With its initial list of alternatives, the Corps project team is to then evaluate each alternative by (1) comparing it to the scenario of proceeding with no project; (2) applying criteria established in the Principles and Guidelines; (3) identifying beneficial and adverse effects of each alternative; and (4) considering other relevant factors, such as compliance with environmental requirements. To identify beneficial and adverse effects of each alternative, the Corps uses four general categories established in the Principles and Guidelines, as shown in table 2. The Corps’ Planning Guidance states that project teams should evaluate alternatives using the four categories of analysis, but the evaluation from two categories—National Economic Development and Environmental Quality—must be included in each feasibility study. According to the Planning Guidance, evaluating projects’ potential costs and benefits through these categories of analysis provides a basis for determining which alternatives should be eliminated from consideration, modified, or selected for further analysis. This evaluation can eliminate alternatives that do not meet planning objectives and may narrow the initial list of alternatives to a final list for more detailed analyses and comparison. Corps officials stated that the process of evaluating alternatives can be iterative and is project specific. The Corps project team then is to conduct detailed analyses of its final list of alternatives to compare them to each other and select a recommended alternative. The project team includes the recommended alternative in a draft report with its analysis. The draft report is made available for review and comment by nonfederal sponsors, federal and state agencies, and other stakeholders. The project team incorporates comments into the report, as appropriate, and determines whether the agency will endorse the recommended alternative. The project team finalizes its feasibility study after internal review. The Corps then prepares a report summarizing the proposed plan—known as the Chief’s report—and submits it to Congress for consideration and potential authorization. Based on our review of Corps guidance and eight selected projects that used natural infrastructure, we found that the Corps typically identified project costs and damage reduction benefits in selecting the alternative, although for some projects it also considered additional benefits, such as recreational benefits. Once a Corps project team develops a final list of alternatives in conducting a feasibility study for a particular project, the project team is to conduct an economic analysis for each alternative. This analysis allows the team to compare costs and benefits directly across the alternatives, including alternatives using natural infrastructure, hard infrastructure, or a combination of the two. Specifically, the project team is to develop estimates for each project alternative’s net economic benefits—benefits minus costs—to identify and select the project alternative with the maximum net benefits. The Corps’ Planning Guidance states that the Corps shall select coastal storm and flood risk management projects determined to have the maximum net benefits. Our review of Corps guidance and eight selected projects identified the following costs and benefits that the Corps generally incorporated into its economic analyses: Project costs. According to the Corps’ Planning Guidance, project costs include three categories: implementation costs, other direct costs, and associated costs. Implementation costs, for example, include planning and design, construction, construction contingency, operations, maintenance, repair, and other costs necessary to implement a project. The eight selected projects that we reviewed included analyses of project costs, which mostly focused on implementation and interest costs. For example, the costs for the Corps’ Jacksonville District Lido Key project included initial construction costs (i.e., beach construction and hard infrastructure designed to reduce shore currents), future beach replenishment costs (i.e., operations related to placing material on beaches to replenish eroding shores), and monitoring costs (e.g., measurement of beach fill, sediment type, and habitat quality). Damage reduction benefits. Reducing damages to existing structures, including homes and commercial buildings, is the primary benefit the Corps considers when identifying benefits for coastal storm risk management project alternatives, according to the Corps’ Planning Guidance. The guidance outlines general steps for estimating damage reduction benefits, which are to be calculated and included in each coastal storm and flood risk management alternative’s economic analysis. In seven of the eight projects we reviewed, the Corps analyzed damage reduction benefits as part of its economic analysis. For example, the Corps’ project team for the New York District Union Beach project determined the potential damage reduction benefits of each alternative by estimating the alternative’s potential to reduce (1) damages to coastal property from flooding and waves, (2) public emergency spending, and (3) administrative costs for the National Flood Insurance Program (see fig. 5). We also found that for some selected projects, the Corps identified and incorporated additional benefits into the projects’ economic analyses, including the following: Incidental recreational benefits. Corps project teams may include in the economic analysis recreational benefits that stem directly from the project alternative but that are incidental to the primary purpose of damage reduction, according to the Corps’ Planning Guidance. Specifically, Corps project teams may include recreational benefits, such as increases in recreational visits because beaches are larger in their economic analysis of project alternatives, but recreational benefits are limited to no more than 50 percent of the total economic benefits used to justify an alternative (i.e., demonstrate that an alternative has greater benefits than costs). After an alternative has been economically justified, the team can use the full estimated recreational benefits with the damage reduction benefits to select the alternative with maximum net benefits. In our review of eight projects, we identified four projects where the Corps project team included recreational benefits in its economic analysis for the project alternative that was selected. For one such project, the Los Angeles District’s Encinitas-Solana Beach project, the Corps’ economic analysis showed that the selected project alternative had lower damage reduction benefits than project costs. However, when the Corps added recreational benefits—as allowed by Corps policy—the combined annual damage reduction and recreational benefits resulted in the alternative having greater benefits than costs (see fig. 6). Other direct incidental benefits. The Corps may also consider other direct incidental benefits in its economic analysis, as appropriate, according to the Principles and Guidelines. In our review of eight projects, we identified three projects that included estimated incidental benefits aside from recreational benefits. The three projects included economic benefits associated with reduced maintenance costs for local communities, whose expenses for maintaining local beaches would decline after the Corps projects were constructed. Other than these reduced maintenance costs, the Corps did not include other types of direct incidental benefits, such as environmental or other social benefits, in the economic analyses for the eight projects we reviewed. According to Corps officials, some project alternatives using natural infrastructure may provide direct incidental benefits that are not included in the economic analysis, such as environmental and social benefits. For example, the draft feasibility study for the New York District’s Jamaica Bay project states that natural infrastructure can provide direct incidental benefits, such as improving ecosystems, filtering water, and improving aesthetics. The Corps acknowledged these incidental benefits and their importance to communities in its draft feasibility study, but did not incorporate these benefits into its economic analysis because they could not be monetized, according to Corps district officials. Corps headquarters officials said incidental benefits that cannot be monetized in the economic analysis are considered in the planning process through the evaluation of other Principles and Guidelines categories. Two reports published by the National Academy of Sciences stated that when assessing project alternatives, the Corps primarily uses qualitative measures to assess benefits that are difficult to monetize but that relegates such effects to secondary status compared to the monetized estimates of costs and benefits. Moreover, a 2004 National Academy of Sciences report found that the Principles and Guidelines outlines a process that focuses on the effects that can be monetized, which does not allow for full consideration of a project’s total economic effects. Nonetheless, for three of the eight projects we reviewed, we found that the Corps modified its approach in selecting the use of natural infrastructure as part of the recommended alternative. For instance, for the Encinitas-Solana Beach project, the Corps granted an exception to its planning process and recommended a locally preferred plan. In certain circumstances, Corps project teams can deviate from the Corps’ Planning Guidance that calls for the Corps to select the project alternative with the maximum net benefits. Corps headquarters officials said that requesting such an exception is the primary method the agency uses for recommending a project alternative that does not meet the Corps maximum net benefits requirement for a project focused solely on coastal storm or flood risk management. For the Encinitas-Solana Beach project, the California Coastal Commission found that the Corps’ proposed alternative with the maximum net benefits was inconsistent with the mission of California’s coastal management program to protect and enhance the state’s coastal environment. In particular, the Commission had concerns about the size of the project and the amount of sand to be added to the beach under the proposed alternative, as well as the potential adverse effects on a nearshore natural reef and marine resources. In response, the Corps’ Los Angeles District worked with the project’s nonfederal sponsors to address the commission’s concerns and revised the project by reducing its size and potentially lessening its environmental impacts. The commission approved the revised project alternative in November 2013. The Corps’ Planning Guidance also allows projects with multiple objectives to incorporate other analyses in selecting a recommended alternative. For the Philadelphia District’s Lower Cape May project, ecosystem restoration was the project’s primary objective, but it also had a coastal storm risk management objective. According to the project’s feasibility study, the project focused on protecting and restoring a freshwater marsh that was being flooded with salt water from storms because of continued beach erosion. The Corps used a cost- effectiveness analysis to meet the primary objective, which compared environmental measures (e.g., the number of acres of habitat restored) with the costs of different alternatives. In addition, this project included a beach component to protect the marsh from saltwater intrusion. In the process of designing beach alternatives, the Corps project team conducted a damage reduction benefit analysis to determine an optimal size for the beach that would provide the greatest net damage reduction benefit to nearby communities. This analysis helped inform the Corps decision to select a beach design option that met the project’s primary objective of protecting the ecosystem, while also providing the most incidental damage reduction benefits to local communities, according to Corps district officials. For the third project, the New York District’s Jamaica Bay project, the Corps incorporated natural features into the project, although it did not directly include the economic benefits of these features in its economic analysis. For the project, the Corps project team recommended an alternative that was designed to address frequent flooding within Jamaica Bay at three locations. The project team incorporated wetlands into the design at one location, along with hard infrastructure. The nonfederal sponsors of the project told us that they advocated for the inclusion of these natural features, where appropriate, because of their risk reduction and ecological benefits. In response to the interests of nonfederal sponsors, the Corps project team developed and recommended the alternative incorporating hard infrastructure, such as floodwalls, along with coastal wetlands. The Corps did not include the risk reduction benefits from the wetlands in the economic analysis, but the draft feasibility study noted that the project was economically justified based on the monetary benefits of the hard infrastructure alone and that the wetlands provided additional benefits that could not be monetized. Based on our literature review, agency documentation, and interviews with Corps officials and other stakeholders, we found that the Corps faces challenges developing cost and benefit information for some natural infrastructure to help inform the process for selecting project alternatives and conducting economic analyses in feasibility studies. Specifically, these challenges related to (1) assessing the performance of some types of natural infrastructure and (2) monetizing the social and environmental benefits associated with using natural infrastructure. The Corps recognizes the need to obtain additional data to better develop cost and benefit information for some types of natural coastal infrastructure, and it has begun taking steps to do so. Information is not readily available on the performance of some types of natural features in reducing coastal storm and flood damages, which makes it challenging for the Corps to develop cost and benefit information for these features and compare them to other alternatives, such as those that use hard infrastructure. For example, Corps headquarters officials said that—in contrast to beaches and dunes—there are significant knowledge gaps about the extent to which wetlands, reefs, and subaquatic vegetation can reduce the risks associated with coastal storms by, for example, moderating wave heights and flooding. In addition, there are knowledge gaps about how these natural features will change over time and how any changes might affect the long-term performance of the features. A Corps report from January 2015 also identified knowledge gaps in understanding how some natural infrastructure, such as wetlands, may perform during coastal storms or floods. According to the report, wetlands may reduce storm surge, but in some instances water can be redirected, potentially causing a storm surge increase elsewhere. Corps officials noted that all structures—whether natural or hard—change over time, requiring maintenance and repair, but said that natural infrastructure may change more dramatically than hard infrastructure and over a shorter period of time. For example, a healthy wetland could restore itself and reduce maintenance costs after a major storm or require the Corps to take action to restore the wetland after the storm event, which could increase the costs of maintaining the wetland. Corps officials also stated that there are knowledge gaps regarding whether wetlands can absorb major storm surges and how these features would perform in the event of recurring coastal storms in a short period of time. Specifically, natural features may be damaged during intense storms (e.g., wetlands can erode and vegetation may be stripped apart), which may degrade the long-term performance of the features. Because the Corps does not have information on performance for some natural features, it has been unable to update engineering guidance to include the use of some natural features, according to Corps officials. A Corps headquarters official explained that the agency must first develop a broader understanding of how some natural features, such as wetlands, perform under various coastal storm scenarios over time before it can begin to develop design guidance for using these features for coastal storm protection and flood risk management projects. A Corps headquarters official said that the agency recognizes the need to obtain additional information on natural infrastructure and has initiated steps to address the challenge related to developing information on the performance of some types of natural infrastructure. In particular, in October 2016, the Engineer Research and Development Center began collaborating with several entities, including other federal agencies, international partners, academic institutions, and nongovernmental organizations, to develop guidelines for using some types of natural infrastructure. According to the scoping document, this effort is to entail developing guidelines to support various phases of building natural infrastructure projects, including conceptualization, design, engineering, construction, and maintenance. According to the Corps official, an anticipated key output from the international effort includes developing information on defining performance for different types of natural infrastructure features and options for measuring performance depending on project objectives. The final product is expected to include chapters with information on analyzing natural infrastructure benefits and related monitoring, maintenance, and adaptive management issues, among others. The Corps official stated that the guidelines will not be official Corps guidance or policy, but Corps project teams and other practitioners can use the guidelines as a resource for identifying best practices in planning projects and assessing potential alternatives. For example, the guidelines will include case studies illustrating design and engineering concepts for certain types of natural features. The guidelines are scheduled for publication in March 2020. The Corps has also developed a separate internal initiative to help fill knowledge gaps regarding how some natural features’ performance can provide benefits relevant to flood risk management, among other benefits. Specifically, the Corps’ Engineering With Nature® Initiative is focused on sharing natural infrastructure best practices that are emerging, and communicating the information to staff in the Corps’ district offices and other key stakeholders. According to a Corps official, the goal of this initiative, among other things, is to help familiarize the Corps’ district staff with existing natural infrastructure information and relevant case studies. The Corps’ Galveston and Philadelphia Districts have projects that may incorporate natural infrastructure. For example, the Galveston District is considering opportunities through the Coastal Texas study to use natural features, such as barrier islands, wetlands, and reefs, in combination with hard infrastructure (e.g., levees), to reduce the risks from storms and floods. Similarly, the Corps’ Philadelphia District is considering a plan to design, construct, and evaluate natural features as part of the New Jersey Back Bays Storm Flood Risk Management study. In addition, in 2018, the Corps’ coastal working group initiated a project within the Corps to help identify natural infrastructure knowledge gaps and prioritize key areas for research based on requests for information received from Corps’ districts. The Corps plans to incorporate information gathered from this project into a strategic plan that is intended to help inform research funding decisions for fiscal year 2020, according to a Corps official. Our review of economic literature identified challenges in estimating the total economic benefits associated with using natural infrastructure features. Several studies noted that data for conducting economic analyses are not readily available. For example, one study noted that there is insufficient information on how restoring wetlands might affect the survival of certain endangered species. Such information is needed, according to the study, to provide insight on the extent to which such features might generate economic benefits. Another study noted that because projects that combine natural features with more traditional structures (i.e., hybrid projects) are relatively new, less is known about their effectiveness or their costs and benefits. Finally, according to another study, estimating recreational benefits associated with natural habitats, such as coastal marshes, can be difficult because there is insufficient information about the extent to which the public visits those sites. In the eight projects we reviewed, Corps project teams did not estimate incidental benefits other than recreational benefits or through avoiding maintenance costs for coastal storm and flood risk management projects. As previously discussed, environmental and social benefits are considered incidental benefits, and Corps guidance indicates that they do not have to be included in the economic analysis. On the other hand, when assessing potential alternatives of coastal storm and flood risk management projects in its feasibility studies, the Corps can quantify or describe the benefits qualitatively and consider these effects during the planning process, outside of the economic analysis. For example, the Corps has measures to quantify changes in habitat, such as number of acres of wetlands restored. The Corps can also qualitatively describe habitat benefits for specific species. However, these nonmonetized benefits may not affect the selection of the recommended alternative, which is generally based on the monetized net benefit estimates of each proposed alternative. The Corps has begun developing a process for identifying, describing, and considering a broader array of potential benefits when assessing natural infrastructure alternatives for specific projects. Specifically, a June 2017 memorandum from the Corps’ Director of Civil Works indicated that projects with coastal storm and flood risk management objectives as well as other objectives should consider social and environmental benefits in the formulation, design, and implementation of projects within existing legislation and Corps policy. A Corps headquarters official said that the agency is not attempting to monetize all potential benefits but is considering options for accounting for potential benefits other than through the traditional monetary assessments of costs and economic benefits. A Corps headquarters planning group is currently working on developing an initiative that would identify a process for using a flexible approach for considering the social and environmental effects of natural infrastructure for coastal storm and flood risk management projects. For example, project teams may have the option of determining whether to incorporate nonmonetized social and environmental benefits, such as enhancing public safety in coastal communities, into the decision-making process for selecting the recommended alternative. The Corps official stated that the agency has begun working on developing guidance for this initiative and expects to issue the guidance in calendar year 2019. We provided a draft of this report for review and comment to the Department of Defense. The department provided technical comments, which we incorporated as appropriate. As agreed with your offices, unless you publicly announce the contents of this report earlier, we plan no further distribution until 30 days from the report date. At that time, we will send copies to the appropriate congressional committees, the Secretary of Defense, the Chief of Engineers and Commanding General of the U.S. Army Corps of Engineers, and other interested parties. In addition, the report will be available at no charge on the GAO website at http://www.gao.gov. If you or your staff members have any questions regarding this report, please contact me at (202) 512-3841 or fennella@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. GAO staff who made key contributions to the report are listed in appendix II. This appendix presents information on the eight projects that we selected for review with coastal storm and flood risk management objectives that the U.S. Army Corps of Engineers (Corps) constructed and that included natural infrastructure. We randomly selected eight projects across Corps districts on the Atlantic, Gulf, and Pacific coasts. In seven of the eight projects, the Corps recommended alternatives with either beaches or dunes as the type of natural features to be used for coastal storm and flood risk reduction (see table 3). According to several Corps district officials we interviewed, alternatives featuring beaches are often most appropriate because other natural features, such as wetlands, would not survive the impacts of the high-energy storm waves in open ocean coastal areas where these projects are located. In addition to the contact named above, Alyssa M. Hundrup (Assistant Director), Leo Acosta (Analyst-in-Charge), Mark Braza, Eric Charles, Timothy Guinane, and Jeanette Soares made key contributions to this report. Important contributions were also made by John Delicath and Sara Sullivan.

Summary: The Corps constructs water resources projects to reduce risks to coastal communities from storm damage, among other things. These projects can involve building hard structures, such as seawalls, to protect against flooding and wave damage. The Corps and some state and local agencies are increasingly considering using natural infrastructure, such as wetlands, to reduce risks from coastal storms and flooding. GAO was asked to review the uses, costs, and benefits of natural coastal infrastructure for the Corps' coastal storm and flood risk management projects. This report describes (1) how the Corps considered costs and benefits for selected projects that used natural infrastructure and (2) challenges the Corps faces in developing cost and benefit information for using natural infrastructure and steps taken to address them. GAO reviewed Corps guidance; obtained information on projects that used natural infrastructure and received funding from fiscal years 2012 through 2017; randomly selected eight coastal storm and flood risk reduction projects from the Atlantic, Gulf, and Pacific coasts; and reviewed each project's planning documentation and economic analyses. Findings from these projects are not generalizable to all Corps' projects. GAO also reviewed economic literature, reviewed Corps documents related to the use of natural infrastructure, and interviewed Corps officials and stakeholders with experience in using natural infrastructure. The U.S. Army Corps of Engineers (Corps) typically identified project costs and damage reduction benefits for the eight projects using natural infrastructure that GAO reviewed. In selecting projects, the Corps is to conduct economic analyses of project alternatives, which may include hard structures, natural infrastructure, or a combination, to compare their costs and benefits. Corps guidance states that for coastal storm and flood risk management projects it is to select the alternative determined to have the maximum net benefits (benefits minus project costs). The Corps calculated project costs for the eight projects, such as planning, design, construction, and maintenance costs. It calculated damage reduction benefits for seven projects by estimating reduced damages to existing structures in the project area, including to homes and commercial buildings. Corps guidance allows the economic analysis to also include incidental benefits of a project, and four projects incorporated recreational benefits of alternatives, such as increases in recreational visits because beaches would be larger. The Corps did not include other types of incidental benefits, such as environmental or other social benefits, for the eight projects. Corps documentation for one project identified environmental benefits of constructing wetlands as part of the project, such as improving ecosystems and filtering water. However, Corps officials said they did not incorporate these benefits into the economic analysis because the benefits could not be monetized. The Corps faces challenges in developing cost and benefit information for some types of natural infrastructure and has initiated steps to address this. For example, a 2015 Corps report identified knowledge gaps in understanding how natural coastal infrastructure, such as wetlands, may perform during coastal storms. These knowledge gaps make it challenging for the Corps to develop cost and benefit information for some natural infrastructure alternatives and compare them to other alternatives, such as those that use hard infrastructure. The Corps recognizes the need to obtain additional data to better develop cost and benefit information and has begun taking steps to do so. For example, in 2018, the Corps initiated a project to help identify natural infrastructure knowledge gaps and prioritize key areas for research. The Corps plans to incorporate information gathered from this project into a strategic plan that is intended to help inform research funding decisions for fiscal year 2020, according to a Corps official.