Putting a price tag on wetlands defense
Fellow studies how wetlands decrease flood damage

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When it comes to flood protection, most people think of man-made barriers like seawalls or sandbags. But nature already has some defenses in place: wetlands. Day to day, wetland plants anchor soil against erosion. They also push back against the waves to lessen the effects of hurricanes and nor’easters.

Wetlands protect the coastline, but engineers and planners need detailed numbers to incorporate natural features into coastline designs. Ali Rezaie, a Ph.D. candidate at George Mason University and a Virginia Sea Grant graduate research fellow, is determining more detailed estimates of wetland protection in the Chesapeake Bay.

Although he’s officially an engineering student in GMU’s flood hazards research lab, Rezaie jokes that he’s a research nomad without a discipline to call home. His work combines engineering, economics, and environmental science.

“I realize that to make changes, from science to policy, there is a common language, and that is money,” Rezaie says. “That’s why, in my Ph.D., I wanted to have a taste of both engineering and economics.”

But before wetland protection can be boiled down to a dollar sign, researchers need a clear picture of how marsh plants combat the small-scale processes like erosion and wave action.

“In order for us to use it as an engineering defense, we need to transition from, ‘Well, they’ve been around and they provide some defense,’ to, ‘How much exactly can we count on these natural features to protect a given infrastructure or community so we can complement that with an engineering design strategy?’” says Celso Ferreira, associate professor of water resources engineering at GMU and Rezaie’s advisor.

Rezaie’s previous work, done in partnership with Resources for the Future, focused on Maryland’s portion of the Chesapeake Bay. He estimated that wetlands could prevent anywhere from $50-450 million in storm damage, depending on the storm. Now, he plans to turn his attention to the lower portion of the bay to estimate the value of wetland protection for Virginia’s coasts.

The GMU researchers will run the model twice: once with the current wetlands in place, and then again with all the wetlands replaced by open land or water. Then they’ll compare how the flooding changed without wetland protection, says Margaret Walls, a senior fellow at Resources for the Future who works with Rezaie.

“Then we have a difference in how much the wetlands are actually doing to lower those flood heights,” Walls says. “Then, using property value estimates, we can translate that into a difference in property damages.”

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Day to day, wetland plants anchor soil against erosion. They also push back against the waves to lessen the effects of hurricanes and nor’easters.

Rezaie and collaborators at The Nature Conservancy and the Maryland Department of Natural Resources have collected a year’s worth of measurements of water level, waves, topography, and marsh plant characteristics in Deal Island, Maryland. These observations ensure that their model will capture the accurate wetland flooding scenarios. Through the Nature Conservancy, the researchers will also publicly share their results to strengthen localized analysis of marshes.

While the model gives a snapshot of how wetlands are now, sea-level rise could change that. Rezaie will use projections to predict how the value of marsh protection might change in the future. For example, marshes may shift closer toward shore to escape rising waters. How communities use land near the marshes could change, too.

“That's where we kind of stop and pass along to the decision makers and the public and managers,” Ferreira says. “If we're successful in building this tool and the scenarios and understanding, we can offer a what-if scenario for the alternatives that are out there.”

TAKEAWAYS

  • Wetland plants can reduce waves, prevent erosion, and lessen storm damage to nearby communities.
  • Rezaie uses economic and engineering techniques to zero in on the how much flooding damage wetlands reduce.
  • Wetlands and marshes might change in response to sea-level rise, and Rezaie will factor in these changes during the modeling.

    Written by Madeleine Jepsen | Virginia Sea Grant

    Photos and Video by Aileen Devlin | Virginia Sea Grant

  • “I realize that to make changes, from science to policy, there is a common language, and that is money,” Rezaie says. “That's why, in my Ph.D., I wanted to have a taste of both engineering and economics."
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    While the model gives a snapshot of how wetlands are now, sea-level rise could change that. Rezaie will use projections to predict how the value of marsh protection might change in the future.