Wetlands Prevent Millions of Flood Damage: Study

Wetlands and floodplains protected Middlebury, VT, from as much as $1.8 million in flood damage during Tropical Storm Irene, a new University of Vermont study finds.

The study is the first to calculate the economic benefits that river wetlands and floodplains provided during the major storms that have struck the U.S. East Coast in recent years.

Researchers analyzed 10 flood events to estimate the value of the Otter Creek floodplain near Middlebury. They found the natural barrier saves the town up to 78 percent of potential damages, or up to $450,000 per year on average.

“These findings show the huge benefits of 'natural infrastructure,'" says lead author Keri Bryan Watson, a PhD student in UVM’s Gund Institute and the Rubenstein School of Environment and Natural Resources.

As floods become more frequent and destructive worldwide, the research – published in Ecological Economics journal – gives regional planners a powerful argument for protecting key wetlands.

“This study shows policy makers the importance of conservation investments that make communities more resilient to the impacts of climate change,” says Deb Markowitz, Secretary of Vermont’s Agency of Natural Resources. “By putting a price tag on wetlands and floodplains, we can demonstrate the value of natural infrastructure to protect communities from the increased risks of flooding from climate-related storms.”

The study also offers researchers an important new method for assessing the value of natural flood barriers.

Floodplains at risk

Wetlands are swampy areas typically located in floodplains, the wide swaths of land along bodies of water. Together they act as sponges to hold excess water and slow it from cascading to low-lying areas.

A Louisiana native, Watson’s childhood home bordered a floodplain. She witnessed small local flooding events, and followed the effects of Hurricanes Katrina and Rita closely.

This personal connection drove her to investigate the financial benefits of natural flood barriers, as global flood risks grow due to climate change and development, she says.

Among the threats to floodplains are the straightening of rivers to keep water away from new residential and business developments. These actions – often to mitigate flooding risk in one area – can wreak havoc on downstream communities. Events like Irene highlight these consequences, she says.

“It’s really a problem of regional coordination, of understanding that everything that happens upstream can affect towns downstream,” says Watson, who conducted the study with UVM’s Taylor Ricketts, Gillian Galford and Jarlath O’Neil-Dunne, with Stephen Polasky of the University of Minnesota.

Nature’s flood protection

The researchers used data from the U.S. Geological Survey, which tracks water levels in Middlebury and Rutland, two towns that bookend the Otter Creek floodplain. This helped Watson study different water levels, and calculate how much more water – and damage – would have struck Middlebury had the floodplain not slowed the deluge.

Using federal flood insurance models, Watson then estimated the monetary damages flooded homes and buildings would have faced. The study didn’t assess town infrastructure: roads, bridges and utilities. That would increase wetland benefits even further, she says.

“Knowing the effects and value of floodplains will help developers and regional planners make better long-term decisions,” says Watson. “These are valuable natural resources we should try our best to protect.”

Key findings

  • During Tropical Storm Irene in 2011, floodplains and wetlands diminished damages in Middlebury, VT, by 84 to 95 percent – saving potentially as much as $1.8 million in flood damages.
  • Middlebury saves an annual average of $126,000 to $450,000 in damages due to the Otter Creek floodplain, which reduced damages by 54 to 78 percent, on average, across 10 flooding events.