Des Moines River in Ottumwa, file photo.

Nitrates in the Des Moines River have caused issues for the Ottumwa Water and Hydro plant, which provides drinking water for Ottumwa. Some are questioning whether long delays in getting results from state reports on nitrates are due to unfavorable results.

OTTUMWA — Experts from across the state knew they could learn something about flood control by coming to Wapello County. So this week, the board of the Soap Creek Watershed invited watershed managers and others to take a tour.

The Soap Creek project extends through Wapello and three other counties: The bus tour took most of a work day to complete.

After a meeting of the board of supervisors this week, Jerry Parker, a Wapello County supervisor as well as the chairman of the Soap Creek Watershed Project, discussed the tour.

“We’ve built 132 structures,” Parker said. “That’s more than every other watershed in the state put together.”

One structure, for example is more dam or levee than actual reservoir. It helps control flooding around one of the roads. In the past, a bridge allowed water to flow right through — or, depending on the flow of the water, taking the bridge with it. After the Soap Creek group considered a better way, said Parker, they replaced the bridge with earth — it stops water, except for a tube running through the structure, which allows some water to get through in a more controlled manner.

“Then, if there’s a flood that washes it away, you replace a $3,000 tube instead of a bridge that costs more than $100,000,” Parker said.

They were able to show off some of the beauty of the area, but Parker said to enjoy it, you really had to “see it with your own eyes.” He’s seen the sites before, so he was able to focus on a different part of the event.

“I think the people we gathered, our speakers, were the highlight,” he said.

A group of scientists who came from the University of Iowa, run the state’s Iowa Flood Center, founded in 2009. The center follows the efforts of watershed management groups across the state because their missions line up.

Parker said the words of flood center director Witold Krajewski were especially validating to him. What the watershed board had been working on all these years seemed to be having a positive effect.

“I gave them the highlights of a technical paper we published in the Journal of Hydrologic Engineering,” said Krajewski. “We realized in Iowa, the landscape does not lend itself to large reservoirs that could aid in flood mitigation. But it’s not completely flat. So instead of one or two large reservoirs for flood mitigation, we could have numerous small reservoirs.”

The theory is not completely untested. Twenty or 30 years ago, someone had a similar vision on a smaller scale.

“We learned there already is a system like that: Soap Creek Watershed, with over a hundred structures,” said Krajewski.

However, the structures had been built not for research but to help property owners in the area. That meant there were no “hydrologic studies” performed using measuring devices or looking at a before and after scenario.

This week, the scientist did get to hear a local resident mention that one particular road used to flood all the time. Now it doesn’t. And that is helpful, he acknowledged. But in order to create change, Krajewski and his team need hard data to show agencies offering research grants. The same holds true for getting the state to make changes: The flood center needs to be able to say something along the lines of, “When this amount of rain falls, with no controls in place, ‘blank’ happens. With a large reservoir 100 miles away, ‘blank’ happens. Or when there are five small structures in place within a few miles, ‘blank’ happens.”

“So we did a simulated study,” said Krajewski. “We monitored what our model does. We extended our computations to where Soap Creek flows into the Des Moines River. The study shows clearly the benefit of the [small-yet-many-structures] system.”

Reporter Mark Newman can be contacted at mnewman@ottumwacourier.com and followed on Twitter @couriermark.

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