The value of US coral reefs for risk reduction - American Samoa
The value of U.S. coral reefs for risk reduction: Facts for American Samoa
- The social and economic benefits provided by all U.S. reefs were rigorously assessed across more than 3,100 km (>1,900 miles) of coastline using hydrodynamic models coupled with census data.
- Annually, reefs in American Samoa provide flood protection benefits to more than 580 people and $33 million in averted damages to property and economic activity.
- With a 1-m loss in reef height, the 100-yr floodplain would increase across American Samoa by 2 km2, imperiling 1,000 more people and $70 million in property & economic activity.
- This study provides the most comprehensive set of flood risk maps across all US coral reef coastlines and the first ever national-scale quantification of flood protection benefits provided by coral reefs.
The degradation of coral reefs raises flood risks by increasing the exposure of coastal communities to storms.
The coastal protection benefits of coral reefs and other natural defenses are not usually assessed in the same rigorous, economic terms as artificial defenses such as seawalls, and therefore often not considered as an option in hazard management decisions. In this study, we combine engineering, ecologic, social, and economic data and tools to provide a rigorous valuation of the coastal protection benefits of U.S. coral reefs across Hawaii, Florida, Guam, American Samoa, Puerto Rico, the U.S. Virgin Islands, and the Commonwealth of the Northern Mariana Islands (CNMI).
Coral reefs act like submerged breakwaters by breaking waves and dissipating their energy offshore before they flood coastal properties and communities. This is an enormously valuable function. In 2017, Hurricanes Harvey, Irma and Maria alone caused over $265 billion in damage across the nation.
First map shows the simulated flooding for 100-year storm events with (blue) and without (red) coral reefs in Tutuila, American Samoa.
[See pamphlet page 2] In this report, we demonstrate that coral reefs provide the U.S. with more than $1.8 billion dollars in flood protection benefits every year. They reduce direct flood damages to public and private property worth more than $800 million annually, and help avert other costs to lives and livelihoods worth an additional $1 billion. Coral reefs annually protect $184 million worth of buildings and economic activity in Puerto Rico, $675 million in Florida and $836 million in Hawaii.
These are not ‘back of the envelope’ numbers. Flood risk was assessed using sophisticated hydrodynamic models and more than 60 years of hourly wave data for U.S. coral reef coast lines – a total area of over 3,100 km (>1,900 miles) of shoreline. We developed flood risk maps projecting the extent and depth of flooding that would occur across a range of storms from the more commonly occurring to the catastrophic, with and without the top 1-m of coral reefs. These flood risk maps were combined with the latest information from the U.S. Census Bureau and the Federal Emergency Management Agency to identify people and properties at risk – and benefiting from the presence of coral reefs – in each location.
Last composite image shows a map of American Samoa with the annual expected benefits ($/km) coral reefs provide in coastal flood reduction.
Rigorously valuing coral reef benefits in this way is a key step toward mobilizing resources to protect them. These maps and values can be used to inform:
- storm response actions & recovery funding
- coral reef conservation areas
- public & private insurance incentives
- benefit : cost analyses for reef restoration
- the consideration of reefs as national infrastructure
Storlazzi, C.D., Reguero, B.G., Cole, A.D., Lowe, E., Shope, J.B., Gibbs, A.E., Nickel, B.A., McCall, R.T., van Dongeren, A.R., Beck, M.W., 2019, Rigorously valuing the role of U.S. coral reefs in coastal hazard risk reduction: U.S. Geological Survey Open-File Report 2019–1027.
Find the report at: https://doi.org/10.3133/ofr20191027
The Value of U.S. Coral Reefs for Risk Reduction
Discover the social and economic benefits provided by other U.S. reefs
Rigorously valuing the role of U.S. coral reefs in coastal hazard risk reduction
U.S. Geological Survey Open-File Report 2019–1027