Frequency of Iowa flooding and precipitation on the rise


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Graph showing the average amount precipitation per year in Iowa. The average amount of has increased dramatically in the state. Since 1960, has seen 10 percent increase in the amount of annual precipitation. (Iowa State University)
Jake Slobe | October 26, 2016

Recent Iowa State University data shows that 100-year flood plain maps actually map 25-year flood plains.  The data also shows that an increasing frequency of large rainfall events throughout Iowa. In Cedar Rapids, the number of heavy rainfall events has increased by 57 percent over the last 100 years.

Kamyar Enshayan, director of the University of Northern Iowa Center for Energy and Environmental Education says that part of the reason for these increases in flooding is coming from changes in land use.

“Over the last 100 years, we have significantly altered the hydrology of our state. The part that we can do something about that would have fairly immediate results is land use change, meaning changing the way our cropping system works, and reestablishing some of the elements we’ve lost like wetlands and forests.”

Currently, the vast majority of Iowa’s agricultural land has, for a long time, been under cultivation in a two-year, corn-soybean rotation. Long-term studies at Iowa State University have demonstrated that moving to a three or four-year crop rotation would lead to a significantly different system that could naturally reduce flooding.

Researchers in Iowa are now analyzing the impact of upstream flood mitigation efforts — as well as determining the costs of potential efforts.

For example, the cost of funding watershed management projects, to help mitigate flood in the state is estimated to be around $5 billion, which is a bargain when put in the context of the cost of flood damage recovery. The damage from the 2008 flood alone was estimated at $10 billion across the state.

Iowa Flood Center completes watershed management sites along Beaver Creek


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Beaver Creek watersheds project engineer Robert Larget provides design details and outcomes at watershed management sites at a tour earlier this month. (Joe Bolkcom/CGRER)
Jenna Ladd | September 27, 2016

Just ahead of major flooding that has plagued northeastern Iowa this month, citizens from communities surrounding the Beaver Creek watershed toured three of six flood control structures in the area that were funded by the Iowa Watersheds Project in 2013.

The project, a part of the Iowa Flood Center’s (IFC) effort to prevent flooding and improve water quality, is the product of a U.S. Department of Urban Housing and Development grant that was awarded to the center following the 2008 floods. The Iowa Watersheds Project provided 75 percent cost-share assistance to landowners to construct water management structures like wetlands and ponds near Beaver Creek, Otter Creek, and South Chequest Creek.

The tour, held on September sixth, marked the completion of the flood prevention structures along Beaver Creek. Participants were bussed to three finished sites along with project engineer Robert Larget, who said that the structures’ designs are encouraging. He said, “The minimal for a hundred-year flood on one site should be in the peak of about twenty-four percent. We have two structures in combination that for that same event will reduce flood flows downstream by about ninety percent.”

Doug Bohlen, a participating landowner near Beaver Creek, said that his structures provide benefits beyond flood control and improved water quality for his family’s land. Bohlen said,

“With my sons and grandsons, it’s going to be good recreation for our family. I’ve always wanted a pond down there, and now there’s one. There’s so many different species of ducks. It’s hard to believe that four days after water started into the pond, there was four swans on it and there was nine sandhill cranes.”

Following the tour, participants listened as IFC civil and environmental engineer Allen Bradley presented an evaluation of the project’s performance. Researchers provided computerized models that are able to predict flood events following major rainfall. Impact differed based on on location, the size of structures, and other factors, but overall, Beaver Creek area residents will see a significant reduction in downstream flooding as a result of the watersheds project.

On the Radio: Iowa organizations work to reduce flooding risks


Photo by U.S. Geological Survey, Flickr.

Listen to this week’s radio segment here or read the transcript below. This week’s episode highlights efforts of two Iowa organizations that are working to reduce flooding risks.

Efforts to increase flood preparedness in Iowa continue four years after the 2008 disasters.

This is the Iowa Environmental Focus.

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DNR: 2010 efforts saved 24,000 tons of soil


Iowa’s waters may be filthy, but according to a DNR release, they could be worse:
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Almost 24,000 tons of soil are staying put on the land and out of Iowa streams, rivers and lakes, thanks to conservation practices installed in fiscal year 2010, according to numbers released by the DNR.

Put that amount of soil in dump trucks, and it would make a line 7.5 miles long. The numbers indicate that conservation practices on agricultural and urban land are effectively reducing pollutants reaching Iowa’s water. Continue reading