Iowa
Wetlands and
Riparian
Areas
Conservation
Plan
Riparian buffers project a national
model
Bear Creek (Central Iowa)
Iowa State University-sponsored research on the use of riparian buffers for soil and water quality is gaining national interest. These pictures, taken at the same location on central Iowa's Bear Creek watershed in 1990 and 1994, show that dramatic improvement in the condition of the streambanks can be achieved in just a few seasons. The Agroecology Issue Team of the Leopold Center for Sustainable Agriculture developed a riparian management system model that integrates a multispecies vegetated buffer of trees, shrubs, and grasses. Also included are bioengineering technologies for streambank stabilization and, often, constructed wetlands to help filter subsurface drainage. These components work together to reduce loadings of nitrate and other pollutants into the stream and turn eyesores into places of natural beauty. They also provide habitat for wildlife and, in some cases, wood products for landowners.
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Streambank stabilization was the first component to be completed at Bear Creek. Researchers used stakes of quick-growing willow to add structure and stability to the bank, biodegradable erosion control fabric to hold soil to the bank, and anchored branches or tree trunks to stop erosion in problem areas. These methods of streambank stabilization are called bioengineering or "soft" engineering.
After the streambanks were stabilized, the multispecies buffer strip had to be established. The first zone of the strip (closest to the stream) is 33-foot wide and is made up of several species of trees, including the willows anchoring the banks. The second zone is 12-foot wide and has many shrub species. The third zone is a 21-foot wide strip of grasses, either a mix of prairie species or a stand of switchgrass. These widths are flexible depending on factors such as erosion levels, pollution potential, and landowner preferences. A 2,900 square-foot wetland was also built in the buffer to filter subsurface drainage before it enters the creek. This buffer system helps protect Bear Creek by adding structure and stability to the soil near the bank, reducing non-point source pollution, slowing surface flow, and encouraging infiltration of precipitation. Restoring riparian systems such as Bear Creek is cost effective and often cheaper than the traditional "hard" engineering methods that offer less aesthetic appeal and wildlife habitat.
Partners in the Bear Creek Riparian Zone Restoration
Project included the Agroecology Issue Team of the Leopold
Center for Sustainable Agriculture, Iowa State University's
Agroforestry Research Team, a local cooperative, the U.S.
Environmental Protection Agency, Pheasants Forever, and Ron
and Sandy Risdal, owners of the research site.
Contact: Tom
Isenhart, ISU Department of Forestry
(515) 294-8056
Richard
Schultz, ISU Department of Forestry
(515) 294-2995
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