Coral Reef Barriers Provide Flood Protection for More Than 18,000 People and $1.8 Billion Worth of Coastal Infrastructure and Economic Activity Annually

Release Date:

Study helps managers take effective actions to reduce the risk to, and increase the resiliency of, U.S. mainland and U.S. insular coastal communities to flooding and other hazards.

This article is part of the April-May 2019 issue of the Sound Waves newsletter

100-year flood areas Maui, Hawaii

Map showing 100-year flood areas, areas with a 1 percent chance of a very large flood in any given year, on the coast of Maui, Hawaii. Blue areas denote those that would flood during a 100-year storm; red areas denote regions that would flood without the presence of coral reefs (marked in gray) and thus are protected by coral reefs. (Public domain.)

Recently, the USGS released the findings of a new, in-depth study titled “Rigorously Valuing the Role of U.S. Coral Reefs in Coastal Hazard Risk Reduction,” funded in part by the U.S. Department of the Interior’s (DOI) Office of Insular Affairs. The study demonstrates annual benefits of coral reefs, including a flood-protection barrier for more than 18,000 coastal citizens and $1.8 billion worth of coastal infrastructure in the United States and its trust territories. The study will help managers take effective actions to reduce the risk to, and increase the resiliency of, U.S. mainland and U.S. insular coastal communities to flooding and other hazards.

“Our Office was glad to collaborate with the USGS and leverage funds available through the Coral Reef and Natural Resources Initiative,” said Doug Domenech, DOI Insular and International Affairs Assistant Secretary. “This highlights the important role that coral reefs play not only for coastal communities in the U.S. mainland, but also in the U.S. insular areas. These research results will be of great interest to the U.S. Coral Reef Task Force, a body tasked to lead U.S. efforts on coral reef ecosystems that the Interior and Department of Commerce chair jointly.”

“As this study shows, USGS science can help save lives, minimize property damage, and reduce risks from natural hazards,” said USGS Director James Reilly. “Information at this fine resolution is critical to coastal managers and planners working on flood mitigation, coastal defense, transportation, and hurricane response and recovery from the local to national scales.”

The research, led by USGS research geologist Curt Storlazzi, analyzed flood risk and assessed reef benefits of populated U.S. reef-lined coasts of Hawaii, Florida, American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands. It is the first time that scientists have combined real-world computer models of storms and waves with engineering, ecological, mapping, and social and economic tools to create detailed, rigorous estimates of the value of coral reef defenses along U.S. mainland and U.S. insular coastlines both in the long-term (annualized) and for more infrequent events such as 50- or 100-year storms.

Underwater, a man wearing a snorkel, fins, and mask swims down to a coral reef with an instrument tied to a tether.

Curt Storlazzi free-dives to set an instrument on the reef off Kauaʻi, Hawaiʻi in March of 2015. (Credit: Amy West, USGS Science Communications Contractor. Public domain.)

The study models can forecast localized threats to people and economic damage in areas with and without coral reefs at a 10-square meter (108 square feet) resolution along more than 3,100 kilometers (1,920 miles) of populated U.S. coral reef-lined shorelines.

Coral reefs, noted Storlazzi, are coastal barriers that can substantially reduce coastal flooding and erosion by reducing the energy of waves as they wash ashore.

“Our goal in this study was to provide sound science to identify where, when, and how U.S. coral reefs provide significant coastal flood-reduction benefits to ultimately save dollars and protect lives,” said Storlazzi. 

The value of coastal flood-risk reduction provided by coral reefs varies from location to location, primarily because of population density and coastal elevation. For example, coral reefs shield more than 3,300 people on Maui each year but just over 100 on Guam, where most housing and infrastructure are located at higher elevations because of the nearly constant threat of typhoons. Coral reefs annually protect $183 million worth of buildings and economic activity in Puerto Rico, $675 million in Florida, and $836 million in Hawaii.

According to Storlazzi, these data indicate that in the event of a 50-year storm (which has a 2 percent chance of occurring in any given year), the economic and protective benefits of coral reefs are even greater. In such a storm, for example, coral reefs off the heavily urbanized coast of Miami-Ft. Lauderdale, Florida, would provide more than $1.6 billion in protection, and off the coast of Honolulu, Hawaii, they would provide more than $435 million in protection.

“This approach represents a massive advance in the precision and resolution of flood risk assessment for ecosystems and in coral reef-lined areas and is an approach that can be applied to other ecosystems, such as coastal vegetation,” said Borja Reguero, University of California-Santa Cruz (UCSC) research scientist. “In addition, the model can be used to assess the impacts of future changes in storms or sea level.”

The study also calculates the extent to which critical infrastructure, such as hospitals, fire stations, roads, and power plants, are protected from coastal flooding by coral reefs.

“We provide clear values of risk and reef benefit to inform key decisions in flood hazard mitigation, storm recovery spending, and coral reef management,” said Michael Beck, UCSC research professor and former lead marine scientist with The Nature Conservancy.

The new report, titled “Rigorously Valuing the Role of U.S. Coral Reefs in Coastal Hazard Risk Reduction,” was prepared by scientists with the USGS, The Nature Conservancy, UCSC, and Deltares. The USGS and DOI Office of Insular Affairs funded the study.

This article is reprinted with small stylistic changes from a USGS news release.

Related Content

Filter Total Items: 1
Date published: July 15, 2019
Status: Active

Coral Reef Project

Explore the fascinating undersea world of coral reefs. Learn how we map, monitor, and model coral reefs so we can better understand, protect, and preserve our Nation's reefs.

Contacts: Curt Storlazzi
Filter Total Items: 8
Date published: June 26, 2019

Coral Reef Barriers Provide Flood Protection for More Than 18,000 People and $1.8 Billion Worth of Coastal Infrastructure and Economic Activity Annually

Study helps managers take effective actions to reduce the risk to, and increase the resiliency of, U.S. mainland and U.S. insular coastal communities to flooding and other hazards.

Date published: June 26, 2019

New Tsunami Evidence Along One of Earth’s Largest Faults, the Alaska-Aleutian Megathrust

Recent geological studies of a key section of the Aleutian Island chain of Alaska suggest Aleutian tsunamis may occur more frequently than previously understood.

Date published: June 26, 2019

After Hurricane Devastation, Sea Turtle Scientists Rebound, Help Rebuild

Seven months after their home base in the Florida Panhandle was demolished by Hurricane Michael, U.S. Geological Survey sea turtle researchers were headed back into the field on May 1, the start of nesting season for Florida's sea turtles.

Date published: June 26, 2019

Recent Coastal and Marine Fieldwork - April-May 2019

In May 2019, USGS coastal and marine scientists visited several coastal and offshore locations, studying reservoir sediment after a wildfire disaster in California, a new remote-control surveying boat in Massachusetts, hypersaline lake sediments in the Dominican Republic, and much more.

Date published: June 26, 2019

Social Media Highlights - April-May 2019

A selection of recent USGS coastal and marine social media posts