Iowa flood planning goes high-tech

New research models offer best data for future protection

The Turkey River runs through Elkader, beneath the Keystone Arch Bridge, on Wednesday, Jan. 23, 2013. The river has floo
The Turkey River runs through Elkader, beneath the Keystone Arch Bridge, on Wednesday, Jan. 23, 2013. The river has flooded several times in recent decades, including a high water level more than 15 feet over flood stage in 2008. The bridge is the longest double-arch stone bridge west of the Mississippi River. (Liz Martin/The Gazette)

Innovative research on northeast Iowa’s Turkey River may herald a breakthrough in state efforts to mitigate future flood damage.

“This really is the first time that hydro modeling has been done in advance of project implementation to get the highest value for the investment,” said Larry Weber, director of IIHR — Hydroscience & Engineering, the parent organization of the Iowa Flood Center.

Iowa Flood Center hydrologists, in cooperation with the Turkey River Watershed Management Authority, have been gathering flow data from scores of sensors, mapping the entire 1.1 million-acre watershed and creating geomathematical models that will enable them to identify areas where the implementation of flood mitigation projects is most likely to reduce downstream damages.

“We are going to do it. We are going to have a positive impact,” Weber said.

He and his colleagues will unveil their findings and specific recommendations for Turkey River flood mitigation projects at a public meeting at 1 p.m. Thursday at the YMCA in Postville.

Targeted effort

“This is the vision for the whole state of Iowa — targeting mitigation projects based on scientific expertise to reduce flood risk,” said state Sen. Rob Hogg, D-Cedar Rapids, who was instrumental in the establishment of both the Iowa Flood Center and the watershed management authorities after the June 2008 floods that caused as much as $10 billion damage in the state.

“It doesn’t mean we will never have another flood, but we can reduce our vulnerability by reducing peak flows,” Hogg said.

Because rates of precipitation and runoff vary at different locations, hydrologists have developed engineering models that describe the land surface and use precipitation and river gauge data to predict stream flow at hundreds of sites, Weber said.

Such models have been used for at least a decade, but only recently have sufficiently fast and powerful computers become available to optimize their use, he said.

“This is one of the most exciting and promising projects I’ve been involved with,” said Rod Marlatt, in his 30th year as director of the Fayette County Conservation Department.

“This whole project was the Legislature’s answer to the floods of 2008, and now we are in a position to find out what can be done to reduce the impact of future floods. It’s invaluable, ” said Marlatt, chairman of the watershed authority that encompasses five counties, 35 towns and cities and several conservation agencies within the Turkey River watershed.

More projects

In addition to the Turkey River research, hydrologists have similar projects under way on the upper Cedar, the middle Raccoon and a pair of Des Moines River tributaries in southern Iowa, Soap and Chequest creeks.

Weber cited peak flow reductions of as much as 40 percent in the Soap Creek watershed after landowners built 134 water retention ponds.

A peak flood reduction of 15 percent would prevent immeasurable damage, said Marlatt.

“Fifteen percent doesn’t sound like much, but it’s a lot when floodwaters are 1/8 inch from the tops of the sandbags, as they were in Elgin in 2008,” he said.

That same year, downstream in Elkader, the Turkey poured into scores of homes and businesses, causing as much as $5 million in damage to the city’s infrastructure and resulting in the buyout of 32 homes, according to City Administrator Jennifer Cowsert, a regular attendee at watershed authority meetings.

Cowsert said the organization provides an ideal means of looking at the entire watershed as a unit with a shared understanding that rain must be managed and controlled where it falls.

“That’s really what it’s all about — taking a watershed approach. We’re all in this together, ” said state Rep. Roger Thomas, D-Elkader, another leader in the establishment of watershed authorities and funding for the Iowa Flood Center’s research.

Perhaps owing to their pride in the scenic Turkey, valley residents share a sense of community that may be lacking in other Iowa watersheds, said Corey Meyer, watershed coordinator with the Winneshiek County Soil and Water Conservation District.

The Turkey River authority also is developing a comprehensive flood control and water quality plan and working with natural resources professionals from several agencies to gather water quality samples at 50 locations, according to Brad Crawford, the Turkey River watershed project coordinator with Northeast Iowa Resource Conservation and Development in Postville.

Iowa has committed about $10 million to watershed management projects, part of $84 million in federal Disaster Recovery Enhancement Funds awarded to the state in 2010. About $5.2 million will be spent on flood mitigation projects identified by the flood center, according to Weber.Researchers will closely monitor the completed projects’ impact on runoff and river levels and present the information to legislators in the hope of securing more funds for more projects, Weber said.

Give us feedback

We value your trust and work hard to provide fair, accurate coverage. If you have found an error or omission in our reporting, tell us here.

Or if you have a story idea we should look into? Tell us here.