Reducing Flood Risks by Restoring Coral Reefs

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Healthy coral reefs are more than just hotspots of marine biodiversity—they’re also invaluable to long-term resilience against coastal storms.

The blue polygons show the results of NOAA surveys of damages to reefs after Hurricanes Irma and Maria in 2017 around San Juan, Puerto Rico. The white bars indicate expected flood risk in the 100-year floodplain before the hurricanes and the colored bar tops indicate how much risk has increased because of damages to reefs per 50,000 square meters (hexagon max width = 277 meters). Public domain.

A new series of reports from researchers at the USGS Coastal and Marine Hazards and Resources Program, the University of California, and the National Oceanic and Atmospheric Administration demonstrates how the restoration of coral reefs along the coasts of Florida and Puerto Rico can save hundreds of millions of dollars in storm-related damages every year.

“We’ve known for a long time that reefs protect coastlines,” said Curt Storlazzi, a Research Geologist with the USGS Pacific Coastal and Marine Science Center and the project lead. “But now, using hazard assessment modeling data that is spatially explicit and rigorously quantified, we demonstrate how reef restoration can further protect coastlines and increase coastal resilience.”

The full height of the bars indicates current expected flood risk in the 100-year floodplain in Miami, Florida. The blue bar tops indicate the risk that could be reduced with reef restoration; their height and color represent the expected benefit from restoration per 100,000 square meters (hexagon max width = 392 meters). Residual risk remains even after reef restoration. The orange line offshore indicates the location of potential reef restoration assessed in the models. The blue polygons offshore represent the extent of current reef habitats. Public domain.

In 2017, Hurricanes Irma and Maria, which were climate-fueled, caused significant damage to coastal communities in Florida and Puerto Rico, not just to infrastructure but to natural barriers such as coral reefs, which help to dissipate wave energy before they flood coastlines.

“In these new reports we’re able to quantify just how much storms can damage our natural infrastructure—our coral reefs—and then evaluate, socially and economically, the consequences of those damages,” said Michael Beck, Research Professor at the University of California, Santa Cruz and co-lead on the project.

The reports assess the coastal protection benefits of reefs in the same rigorous, economic terms that are usually reserved for artificial defenses such as seawalls and bulkheads.

“Those artificial defenses are supported by cost-benefit analyses—the hazard risk reduction benefits are compared to the cost of the built structures,” said Storlazzi. “What we’ve done is to quantify hazard risk reduction for potential coral reef restoration along Florida and Puerto Rico, finding that the cost-to-benefits for reef restoration are very high, in many cases much higher than costs.”

The reports also assess how, in the absence of restoration, coral reefs in Florida and Puerto Rico will continue to decline, further increasing the risk of flooding.

“In order to be able to protect our reefs, we have to know how valuable they are at protecting us,” said Beck.

And that is precisely what the reports find: Coral reef restoration across Florida and Puerto Rico could prevent more than $270 million annually in damage to buildings and economic interruption. “Identifying where reef restoration could provide the greatest value is incredibly important, both for where we should be funding disaster recovery efforts, as well as where we can focus future resilience-building efforts,” said Beck. By working with nature, the reports conclude, we can reduce present and future risks to coastal communities and save coral reef ecosystems at the same time. Video Transcript View audio described version. The increasing risk of flooding along our coasts is driven by climate change, development and habitat loss. Powerful climate-fueled hurricanes such as Irma and Maria in 2017 caused significant damage to coastal communities in Florida and Puerto Rico, not just to infrastructure but to natural barriers such as coral reefs, which help to dissipate wave energy before they flood coastlines. Three new reports from the U.S. Geological Survey, the University of California and the National Oceanic and Atmospheric Administration quantitatively assess how coral reefs damaged by those hurricanes increased flood risk significantly, to the tune of hundreds of millions of dollars. The reports also assess how, in the absence of restoration, coral reefs in Florida and Puerto Rico will continue to decline, further increasing the risk of flooding. But the reports find reason for hope: Coral reef restoration across Florida and Puerto Rico could prevent the loss of more than$270 million annually from flooding.

By working with nature, the reports conclude, we can reduce both present and future risks to coastal communities and save coral reef ecosystems at the same time.

Peter Pearsall, USGS

(Some content used with permission)

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Date published: September 7, 2021
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Quantifying Flood Risk and Reef Risk Reduction Benefits in Florida and Puerto Rico: The Consequences of Hurricane Damage, Long-term Degradation, and Restoration Opportunities

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 because of population growth and climate change. Hurricanes Irma and Maria in 2017 were particularly devasting to humans and natural communities. The coral reefs off the State of Florida and the Commonwealth of...

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August 30, 2021

Reducing Flood Risks by Restoring Coral Reefs

View audio described version.

The increasing risk of flooding along our coasts is driven by climate change, development and habitat loss.

Powerful climate-fueled hurricanes such as Irma and Maria in 2017 caused significant damage to coastal communities in Florida and Puerto Rico, not