Role of Reefs in Coastal Protection

Science Center Objects

We are combining ocean, engineering, ecologic, social, and economic modeling to provide a high-resolution, rigorous, spatially-explicit valuation of the coastal flood protection benefits provided by coral reefs and the cost effectiveness of reef restoration for enhancing those benefits.

View looks across a tropical coastal area with puffy clouds, palm trees, buildings, clear ocean water, and gentle waves.

Waikīkī from atop Diamond Head. Photo credit: Zetong Li on Unsplash

The Problem

View of a coastal city from the sky, with polygons drawn along the coast to show flooding areas.

Map showing the simulated flooding for a 100-year storm event with (blue) and without (red) coral reefs in San Juan, Puerto Rico. The red area thus represents the area protected by coral reefs.

Coastal flooding and erosion from extreme weather events affect thousands of vulnerable coastal communities. The impacts of coastal flooding are predicted to worsen during this century owing to population growth and climate change. There is an urgent need to develop better risk reduction and adaptation strategies to reduce coastal flooding and associated hazards. There is growing national recognition of the role of natural and nature-based solutions to address coastal risks. The biggest limitation to advancing the use of natural defenses in coastal management, however, is the lack of quantitative assessments of their engineering performance and economic benefits. Coral reefs, in particular, can substantially reduce coastal flooding and erosion by dissipating as much as 97 percent of incident wave energy. Reefs function like low-crested breakwaters, with hydrodynamic behavior well characterized by coastal engineering models. Indeed, the need for approaches that use state-of-the-art hydrodynamic and economic models to quantify risk reduction in monetary terms has been widely acknowledged and, thus far, unaddressed, particularly at regional scales. There are currently no comprehensive, high-resolution maps of the benefits or cost effectiveness of coral reef restoration for coastal flood risk reduction. Without this information, it is not possible for Federal, State, Territorial, and local governments and communities to include coral reef restoration in flood recovery and mitigation efforts.

United States coastlines plotted with the expected annual benefits in dollars of having coral reef-lined coastlines.

Map displaying the distribution of total economic losses (direct building damages and indirect economic disruption) in the U.S. that are prevented from flooding by coral reefs annually. In total, the annual coastal flooding risk reduction benefits provided by U.S. coral reefs exceed $1.8 billion.

Our Approach

We are combining hydrodynamic, coastal engineering, geospatial, social, and economic modeling to provide a high-resolution, rigorous, spatially explicit valuation of the coastal flood protection benefits provided by coral reefs at present across, and the cost effectiveness of reef restoration for enhancing those benefits. Our risk-based methods follow probabilistic risk assessment approaches used by the insurance industry and by FEMA and NOAA for the quantification of baseline risk and risk-reduction measures. We are assessing the benefits provided by reefs under present conditions and for different coral reef restoration scenarios. The restoration scenarios cover the range of risk reduction effects that restoration projects could provide, and therefore can pinpoint sites where restoration will be most beneficial and/or cost-effective. We are calculating spatially explicit values of the cost effectiveness of coral reef restoration and making them available in maps through a widely used, web-based, interactive, online decision-support tool.

For more information, see our web page, “The Value of U.S. Coral Reefs for Risk Reduction.”

Caption for large photo at top of page: Wave breaking over a corals on the reef flat off Kwajalein Island.

Please also see the associated efforts on the Coral Reef Ecosystem Studies (CREST) Project website: