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Helping communities plan for increasing rainfall

New guide explores the roles of citizens and communities in flood prevention
Thursday, December 17, 2015
Aerial of the flooded golf course

With the potential for storms to become more frequent and more intense in a changing climate, communities are taking a new look at how they manage rainwater and flooding. Minnehaha Creek Watershed District (MCWD) partnered with two Twin Cities' communities – Minneapolis and Victoria – on a federally-funded study that sheds light on the impact of these changes in rainfall and how they and communities like them can adapt. The process they followed is covered in the new guide Community Adaptation Planning for Changing Landscapes and Climate produced by MCWD.

In the study, funded by a grant from the National Oceanic and Atmospheric Administration's (NOAA) Sectoral Applications Research Program, researchers led a planning process that serves as a model for other cities to follow. First, they determined each study area's vulnerability to increased rainfall and which locations face the most risk. Then they brought in community leaders and technical professionals to figure out the best ways to reduce these risks. Finally, they estimated the costs of these approaches.

To assess vulnerability to flooding, three mid-21st century weather projections were calculated: optimistic, moderate and pessimistic. Due to the small Minneapolis study area's dense population and large number of streets, rooftops and other hard surfaces, researchers concluded that a portion of its stormwater pipes would be undersized under all three weather projections unless system changes are made. Victoria, by contrast, has more room to handle increasing rainfall because only 15 percent of the land is covered by hard surfaces and 30 percent is comprised of lakes and wetlands.

Among the strategies considered during the study were "low impact" development practices that allow rain to soak into the ground instead of running off the landscape. For developing communities that still have large areas of unbuilt land, the study suggested preserving green space and areas that can hold excess water and prevent flood damage. For more densely populated areas, costs of adaptation are higher but solutions are still achievable.

There is no "one size fits all" approach. Communities will have different needs, vulnerabilities, and options for adapting. Check out the planning guide. The study was a partnership between NOAA, Minnehaha Creek Watershed District, City of Minneapolis, City of Victoria, Syntectic International, Antioch University New England and the University of Minnesota. 

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