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Wetland improves flood control, water quality

Wetland improves flood control, water quality

  • Updated

COWELL, Iowa — The wetland and CRP grasses and flowers on farmland owned by Doug Bohlen’s father, Randy, are reducing flooding, removing nitrates from tile water and creating wildlife habitat.

“I’m proud of this area,” said Doug Bohlen, who is in charge of planning for his 89-year-old father’s farm, which sits at the headwaters of Beaver Creek. “It’s finally starting to develop the way I wanted. There is all kinds of wildlife. Hopefully what we’ve done here will take off and go into other watersheds.”

The wetland is part the Beaver Creek Watershed Project, which includes five other wetland structures north and east of Colwell on the Floyd/Chickasaw County line. These wetlands coupled with two existing Conservation Reserve Enhancement Program wetlands and a farm pond in the upper Beaver Creek Watershed are making a difference in holding water and soil on the land and improving water quality, said Dennis Sande, district NRCS conservationist in Floyd and Chickasaw counties.

The $1.5 million Beaver Creek project, part of the Upper Cedar Watershed Management Improvement Authority, was an Iowa Watersheds Project along with Otter Creek in the Turkey River Watershed in northeast Iowa and South Chequest Creek in the Soap/Chequest Watershed in southeast Iowa, said Sande.

In 2010, the U.S. Department of Housing and Urban Development awarded the Iowa Flood Center $8.8 million for the Iowa Watersheds Project. The goals were to maximize soil water holding capacity, minimize severe erosion, manage water runoff and reduce and mitigate flood damages, Sande said.

As the Iowa Watersheds Project ended in the fall of 2016, Iowa was awarded $96.9 million for a new watershed project, the Iowa Watershed Approach. The IWA is working in nine new watersheds across the state and is built off the framework developed by the IWP.

Larry Weber, cofounder of the Iowa Flood Center and executive associate dean of the University of Iowa Engineering College, likens the watershed effort to Johnny Appleseed, strengthening flood protection infrastructure one watershed at a time.

“We’re taking what works in these first watersheds and applying it to others,” he said.

The Bohlen family and the other participating landowners received 100 percent cost-share assistance to construct wetlands on their properties, and permanent easements are in place.

Hydrologic models demonstrate the Beaver Creek wetlands increased flood storage by 141 percent, and reduced peak flows near project outlets by 20–90 percent for small (10-year) and large (50-year) floods. The wetlands also reduced downstream peak flows on Beaver Creek by 10-30 percent for small (10-year) and large (50-year) floods, according to Iowa Flood Center information.

In addition to holding water on the land, Chris Jones, a University of Iowa research engineer, said the wetlands are capturing between 40 and 86 percent of the incoming nitrate that would otherwise have entered Beaver Creek from those tiles.

“As far as the effect on the watershed as whole, we have not crunched the numbers on that yet,” Jones said. “Of course intuitively we know there is an effect.”

Completing the permits and designs for the Beaver Creek wetlands was a long process, Sande said.

“There was incredible cooperation among everyone involved in the Beaver Creek project,” he said. “Floyd County volunteered to be the entity applying for grant.”

The other Beaver Creek flood control wetlands, ranging in size from 1.6 to 3.9 acres, are deeper rather than wide and shallow like the Bohlens’ due to sloping terrain.

Sande had been impressed by the effectiveness of the county’s CREP wetlands in removing nitrates. The Beaver Creek wetlands were not large enough to qualify as CREP sites, but the principles were applied. The engineer who designed all the county’s CREP sites also designed the Beaver Creek wetlands.

A founding member of Pheasants Forever who has been planting trees, shrubs and grasses for many years, Bohlen loves the habitat created by the project.

Just four days after the wetland started filling with water in 2015, four swans were swimming in the pool. He and friends have witnessed hundreds of ducks and geese on the pond during spring migration, and he and his wife recently saw six sandhill cranes. He and his sons are building a cabin near the wetland using mostly reclaimed materials.

There are 460 row crop acres draining into the Bohlens’ 7.9-acre shallow water wetland. The easement consists of 19.3 acres so the area can hold additional water during floods. The surrounding buffer is planted to native grasses and flowers as well as white swamp oak, black walnut and maple trees.

Bohlen said the area has always been wet.

“They tried to tile it, but 11 acres was never farmed. It was slough area,” he said. “Now we have added to it. We have 30 acres of CRP and wetlands.”

“The wetlands have definitely help with washing on the road, driveways and the ground on the other side of the road,” said farmer Rod Hinz, who owns the land where the southernmost wetland is located. “Because the wetland releases water at a slower pace, we see less flooding in our cattle pasture too.”

Bohlen hopes to get the word out to other farmers about what they’re doing in the Beaver Creek Watershed.

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