Statewide floodplain maps near completion

Associate Director Nathan Young outlines the benefits of the Iowa Flood Center’s statewide Floodplain Mapping Project. (Jenna Ladd/CGRER)
Jenna Ladd | November 29, 2016

The Iowa Flood Center hosted an event yesterday to mark the completion of its statewide Floodplain Mapping Project.

In partnership with the Iowa Department of Natural Resources (DNR), the Iowa Natural Heritage Foundation, and the Federal Emergency Management Agency (FEMA), the Iowa Flood Center (IFC) is wrapping up a nearly four year effort ahead of schedule. The Draft Flood Hazard Maps delineate boundaries of flooded areas for 100-year (1 percent annual chance) and 500-year (0.2 percent annual chance) for 85 of Iowa’s counties. IFC’s efforts are focused on those counties that were declared Presidential Disaster Areas following the 2008 floods. Iowa’s remaining 14 counties are being mapped by the Army Corps of Engineers and are expected to be complete over the next calendar year.

The standing room only event featured a presentation by the project’s Associate Director, Nathan Young. Young said, “We’ve been able to either create or update floodplain maps across the entire state that can be used by people in large cities or out in rural communities to better understand their flood risk.” In addition to 100 and 500-year boundary maps, Flood Risk Management Maps are available to Iowans, thanks to a partnership with the Iowa Natural Heritage Foundation. These maps provide Scour-prone floodplain areas, flood depths, and gradients of flood risk.

Information from both flood mapping products will be shared with the (FEMA). Young said,

“The majority of the information produced is available for people to make their own decisions about how to address their flood risk. In some cases the DNR and FEMA have been able to generate enough funding to take our products through the review process and have them adopted by the National Flood Insurance Program. The 100-year floodplain boundary on those maps will be used to establish flood insurance rates.”

Researchers used recently collected light detection and ranging (LiDAR) data provided by the DNR to map all streams in Iowa which drain to one square mile or more. The statewide mapping project is five to ten years ahead of national flood mapping efforts, IFC Director Witold Krajewski reported in his opening remarks.

Beyond providing Iowa citizens with real-time floodplain maps, water resources engineer Harvest Ellis said that IFC has encouraged DNR to use the information available in the flood maps to inform state-led flood mitigation efforts.

Both the Draft Flood Hazard Maps and the Flood Risk Management Maps are available for public use at

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