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Beavers Build Flood Resilience
According to "Shelter from the Storm: How Wetlands Protect Our Communities from Flooding," Spring 2015, Environment America: "The ability of wetlands to hold large amounts of water enables them to serve as a key protection against flooding. During times of heavy precipitation, wetlands act as a sponge – slowing the velocity of runoff and retaining excess water, thereby reducing the danger of flooding. Once captured by a wetland, excess water evaporates, settles into the soil to replenish groundwater, or is slowly released over time....The flood protection that wetlands provide is valuable. According to one study, inland wetlands in the United States provide over $237 billion in water flow regulation services annually."
​Milwaukee River Watershed Study Demonstrates That Beaver Dams Upstream Decrease Flooding Downstream
A 2020 study of the Milwaukee River watershed, "Hydrological Impact of Beaver Habitat Restoration in the Milwaukee River Watershed," demonstrated that beaver dams on the upper reaches of a watershed significantly decreased flooding downstream. The study was conducted by Milwaukee Riverkeeper, the Milwaukee Metropolitan Sewerage District, and University of Wisconsin Milwaukee. The study used the The Beaver Restoration and Assessment Tool (BRAT) to estimate the likelihood of beaver dam building activity and beaver dam capacities in the Milwaukee River watershed, based on GIS analysis of the stream network, vegetation cover, and stream power under baseflow and high-flow conditions. The simulations showed that peak flow rates were reduced by 6% to 48%, and flood flow volumes were reduced by 14% to 48%, depending on the development stages of beaver dams, and actual storm characteristics. Two factors contribute to peak flow reduction: (1) flow interception by storage capacity of beaver dams makes the primary contribution; and (2) energy dissipation through dam overflow when the storage capacity is filled. ​
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​For More Information on How Wetlands Mitigate Flooding
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Flood Damage Reduction in the Upper Mississippi, Wetlands Initiative
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UWM researchers find that beavers could be a remedy for downstream floods
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Hydrological Impact of Beaver Habitat Restoration in the Milwaukee River Watershed
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New Study Finds Beavers Could Be Key To Preventing Flooding On The Milwaukee River
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Battered by Floods, US River Towns Turn to Wetlands
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Flood Reduction through Wetland Restoration: The Upper Mississippi River Basin as a Case History
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Shelter from the Storm How Wetlands Protect Our Communities from Flooding, Environment America
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The beaver effect: How nature's engineers restore wetlands, control floods, and protect rivers
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