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  • Riparian Corridor-Channel Restoration and Management in Elm Creek, Minnesota
  • Christian Lenhart, Research Associate, Britta Suppes, Research Assistant, Kenneth Brooks, Professor, and Joseph Magner, Senior Hydrologist

The University of Minnesota’s Center for Integrated Natural Resources Management, with funding support from the Minnesota Pollution Control Agency and Martin County Soil and Water Conservation District, established a multipurpose stream restoration on an impaired reach of Elm Creek, a 700 km2 subwatershed of the Minnesota River Basin in south central Minnesota. The purpose of the project was to demonstrate cost-effective stream restoration techniques within an economically productive agroecosystem to enhance channel stability, reduce sediment loads, and improve aquatic and riparian habitats. Along with its ecological and agricultural benefits, the project site serves as a unique opportunity for public education and outreach, featuring affordable alternatives for stream restoration, agroforestry practices, and cattle grazing management in southern Minnesota.

Elm Creek is a substantial contributor of sediment to the Blue Earth River, the largest supplier of streamflow (46%) and total suspended solids (55%) to the Minnesota River (MPCA 2005). Draining approximately one-fifth of the state of Minnesota, the Minnesota River is of particular concern because it transports a disproportionate amount (88%) of the total sediment entering the Upper Mississippi River Basin (Engstrom et al. 2009). Accelerated sedimentation causes turbidity levels to exceed total maximum daily load (TMDL) standards and is also detrimental to aquatic biota. Engstrom and others (2009) found that the majority of sediment entering the Upper Mississippi River in recent decades originates from stream channel, ravine, and bluff erosion in the Minnesota River Basin (MRB). Increased rates of channel erosion have been caused by recent tile drainage expansion, land cover change, and precipitation increases. Cumulatively, native prairie conversion, extensive annual cropping, wetland drainage, ditch construction, and artificial subsurface drainage have increased stream flow throughout the MRB (Lenhart 2008), with continued soybean and corn expansion and subsurface drainage increases in the past 30–40 years. A 10%–15% increase in annual precipitation in southern Minnesota over the last three decades has likely contributed to increased streamflow as well.

Though less widely recognized, the straightening of streams at road crossings has also exacerbated channel [End Page 240] instability by decreasing channel sinuosity and instigating channel evolution. Elm Creek has lost approximately 15% of its length since 1938. Increases in slope and streamflow promote channel downcutting and subsequent channel adjustment until a new equilibrium state is reached (e.g., Schumm et al. 1984). However, within the MRB, altered flow regimes and channelization have kept streams in disequilibrium and reduced floodplain connectivity.


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Table 1.

Timeline of restoration activities at the Elm Creek restoration site in the Blue Earth River watershed of Minnesota.

The watershed-scale disequilibrium in the MRB makes intensive streambank stabilization projects infeasible. While watershed management has helped reduce sediment loads, reductions of in-stream sediment sufficient to meet turbidity standards may also require extensive reduction of sediment from stream erosion, which is not economically viable or sustainable. Therefore, targeting channel reaches exceeding some threshold rate of lateral migration is needed.

Since row-crop agriculture is the major economic driver in the MRB, covering 86% of the watershed, channel stabilization projects must address agroeconomic considerations. Multipurpose riparian management systems such as the Elm Creek restoration site are an attractive option because they provide a tool to help meet sediment reduction goals while maintaining agricultural productivity through perennial crop systems and managed grazing. Successful implementation depends on the acceptance by participating landowners, which is strongly influenced by economic incentives.

The Elm Creek watershed consists of flat to rolling topography typical of the glacial Des Moines Lobe till plain, which contains fine-textured, loamy soils. Historically, land cover was predominantly prairie with numerous small lakes and wetlands, or prairie potholes. The project site was about 11 ha of riparian area located in a broad alluvial valley about 6.5 km from the stream terminus at the Blue Earth River, near Winnebago, Minnesota, and close to a county road for easy public access and high visibility. The Elm Creek site exemplified problems common to streams of southern Minnesota, including channel entrenchment, loss of channel sinuosity, floodplain disconnection, and...

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