Leopold Center for Sustainable Agriculture

Flood workshop: How our rivers have changed

Back to Leopold Letter Winter 2008

Iowa’s river systems have changed, most drastically within the past several decades. And although some of those changes are scientifically predictable, Iowa's land use policies and practices have been inadequate to deal with the natural result of those changes – flooding.

Members of the River Systems panel were Keith Schilling, research geologist at the Iowa Department of Natural Resources; Iowa State University Natural Resources Ecology Management assistant professor Tom Isenhart; and Mark Ackelson from the Iowa Natural Heritage Foundation, who worked extensively with landowners after the 1993 floods.

Their recommendations included the need to recognize that flooding is a natural occurrence, the creation of new flood plain maps, and curtailing the development in flood plains. Buy-out programs for existing structures on flood plains and permanent conservation easements are the best ways to mitigate the effects of future flooding.

Schilling said hydrologic studies of Iowa’s major rivers show an overall increase in flow, particularly in base flow during April, May and June. He said increased flows could be attributed to an ongoing rise in precipitation (possibly 10 percent over 40 years, according to one study), changes in land use and land cover, and tile drainage, which adds to a stream’s base flow.

“The changes we’ve seen in the Cedar River and across Iowa are indicative of what has been seen throughout the Upper Midwest,” Schilling said. Many of these changes are caused by a change in land use, such as a sharp increase 20 years ago in production of annual crops (corn and soybean) and away from diverse systems of alfalfa and pastures that have less runoff after rainstorms. Urbanization also has contributed to “flashiness” of streams.

Isenhart said a stream’s response to increased speed and flow of water is predictable. “It’s a law of physics,” he said. “Anything we do to land use, to channelization that increases the amount or speed of water, we will be transporting more sediment in the stream and add to stream meandering.”

He said one study showed that about 3,000 miles of Iowa streams were lost during the 1970s due to large channelization projects, which also reduced in-stream reservoirs for water. Most streams naturally flood every year to two years as a way to dissipate energy.

Ackelson has seen those changes – and their impacts on landowners in the flood plain – first-hand. “There are farmers who have no farm left, the land has been scoured down to bedrock and others whose soil went to the next farm below them.”

He said more funding is needed for conservation easements and buyouts in flood plains. He cited the cases of 654 Iowans who own 62,000 acres of flood-damaged farmland and have applied for a government program to set up permanent easements on their property following the 2008 flooding. He said Iowa will receive $21 million, enough to provide easements for only 26 landowners or about 4,700 acres.

In addition to active flood mitigation and buyout programs, Ackelson said he would like to see conservation compliance enforced for those who receive state tax credits for agricultural land and federal farm support payments. “I contend that no conservation, no dollars. We should expect that of everyone, urban and rural. New development in urban areas should not get tax abatements. We shouldn’t tolerate them not looking out for our water, flood damage and our environment,” he said.

Back to Leopold Letter Winter 2008