Wetlands Reduce Flooding

Wetlands form in low spots on the landscape. Often likened to sponges and described as "nature’s hazard insurance," wetlands store rain that runs off the land and slowly release it to the atmosphere, groundwater, and adjacent lakes, rivers, and streams. While the ability of any particular wetland to reduce flood damages varies, strategic wetland protection and restoration can help reduce flood peaks and damage, protect human health and safety, and reduce the need for expensive projects such as levees, detention ponds, and the reconstruction of flood-damaged roads.

"The Pardeeville dam has breached... impacts to downstream communities in Portage are not expected due to a massive wetland complex between the two cities." ~ From Wisconsin Emergency Management’s Situation Report on Storm # 37, June 14, 2008, 11:20 am

The Greenseams Program, an innovative flood management initiative of the Milwaukee Metropolitan Sewerage District (MMSD) permanently protects key undeveloped lands in the region’s urbanizing watersheds. As of spring 2009, the 1,287 acres of hydric (wetland) soils protected or restored store an estimated 830 million gallons of water. These wetland acres are hard at work reducing flood risks and damages for the 1.1 million residents and 28 communities in the greater Milwaukee area. Click here for details on the MMSD Greenseams program.

Did You Know?

• An acre of wetland prevents between $36,000 and $51,000 in flood damages each year for the cities of Lynwood and Renton in the state of Washington.
• In the Charles River Basin (Massachusetts), an 8,500 acre wetland complex of freshwater marshes, floodplain forests, and lowland hardwood swamps prevents approximately $40 million in flood damages each year.

Note: These quick facts have been compiled from the resources listed below.

Additional Resources on the Ability of Wetlands to Reduce Flood Peaks and Damage

• Increased Flood Storage -- Wetland Habitat Values, Ducks Unlimited (2009).
• Wetlands: Protecting Life and Property from Flooding, U.S. Environmental Protection Agency (2006).
• The Economic Value of the World’s Wetlands, World Wildlife Fund (2006).
• Direct and Indirect Impacts of Urbanization on Wetland Quality, Center for Watershed Protection (2006). See page 8.
• Natural Values -- The Importance of Wetlands and Upland Conservation Practices in Watershed Management: Functions and Values for Water Quality and Quantity, Ducks Unlimited Canada (2004). (Pages 13-28).
• The Economic Value of Wetlands: Wetlands' Role in Flood Protection in Western Washington, Washington State Department of Ecology (1997).
• Flood Damage Reduction in the Upper Mississippi River Basin: An Ecological Means, The Wetlands Initiative (2004).

Peer-Reviewed Journal Articles:

• Hey, D. L. and N. S. Philippi. 1995. Flood reduction through wetland restoration: The Upper Mississippi River Basin as a case study. Restoration Ecology 3:4-17.
• Hey, D.L., J. Kostel, and D. Montgomery. 2009. An Ecological Solution to the Flood Damage Problem. In Finding the Balance between Floods, Flood Protection, and River Navigation, Saint Louis University, Center for Environmental Sciences. Click here for the online PDF version.

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