Demonstration of Streambank Stabilization for Submerged Vanes
Wisconsin Department of Natural Resources
Basin Program Funds:
North Fish Creek, a northern Wisconsin tributary to Lake Superior, is an important recreational fishery experiencing loss of aquatic habitat due to increased flooding and sedimentation. North Fish Creek is similar to many northern Wisconsin tributaries in providing some of the highest sediment loads observed in the Great Lakes basin. The majority of the total sediment load (67 percent, 15,000 metric tons per year) originates from erosion of about 17 large bluffs along the upper main stem of the creek. Upstream controls on erosion are needed to reduce downstream transport (potential scour effects) and sedimentation rates (covering of spawning beds). Past efforts to stabilize the bluffs on North Fish Creek through bioengineering efforts (using living plants to protect stream banks) have failed.
Agricultural and logging activities over the last 100 years have caused increased flooding, erosion and subsequent sedimentation in North Fish Creek. The project area is remote, with steep topography, a lack of roads, heavily forested, and swampy land. Techniques for stabilizing bluffs and reducing erosion on tributaries such as North Fish Creek need to be appropriate for remote areas to assure minimal disturbance of the channel and spawning beds. Submerged vanes are cost-effective low impact alternatives to traditional bank structural measures or measures such as detention basins that reduce flood peaks. They are environmentally less intrusive because they are installed by hand and the bank is left in its natural state. They consist of plates distributed along a portion of the channel that protrude from the channel bed, and are oriented at an angle to the local stream velocity. They modify the secondary flows that are the cause of erosion along the toe of a bank in a meander bend, stabilizing a channel reach without inducing changes upstream or downstream of the vanes.
The Wisconsin Department of Natural Resources (DNR) partnered with the University of Wisconsin-Madison (UW-Madison), the U.S. Geological Survey (USGS), the Natural Resources Conservation Service (NRCS) the U.S. Fish and Wildlife Service (FWS) cooperated to study the effectiveness of submerged vanes for reducing bank erosion and improving aquatic habitat. Personnel visited and evaluated the proposed sites for vane installation several times throughout the project. Project personnel performed bluff and channel surveys to help determine locations for vane installation. Eight channel cross sections were completed and will be used to monitor the shape and condition of the channel prior to and following vane installation.
Project personnel designed and installed a total of 11 vane arrays (cross sections containing vanes). The vanes are approximately three feet long by one foot high prolyethylene (HDPE) that when inserted in the bank, stick up about 2-5 inches above the water level at low flow. A streamflow gagging station was reactivated and will be used to help identify flood conditions experienced after vane installation. After installation, project personnel completed site surveys of the eight transects previously established. The submerged vanes appeared to be working by directing flow away from the eroding bluff.
This study extends over a four-year period. Project personnel are performing laboratory experiments in a flume to determine the most effective vane design through altering vane dimensions and angles of orientation. Another site was established for vane installation and three transects were surveyed. The project team will install vanes there in the near future. If the vanes are effective in stabilizing the channel and bluff, they may be installed at other bluff sites along Lake Superior tributaries.
See also the USGS web site: http://wi.water.usgs.gov/projects/sw/9ko33.htm
Contact: Ms. Kim Walz, 608-264-9220