Shiawassee Conservation District Stops Tons of Sediment from Entering the Shiawassee River
Shiawassee Conservation District
Erosion and downcutting before rehabilitation
Through the efforts of the Shiawassee Conservation District, the severely eroded outlet of the State Road Drain at the Buzz Howe Bridge on Chipman Road was repaired in the fall of 2012. The State Road Drain empties directly into the Shiawassee River and the erosion has contributed significantly to the amount of sediment and sediment deposition in the Shiawassee River. Sediment is a significant pollutant that causes impairments to the aquatic habitat throughout the Shiawassee River Watershed.
The State Road Drain was established in 1889 by Shiawassee County and is a 4.3 mile agricultural ditch emptying into the Shiawassee River. The lower reach of this drain has been considered unstable with significant downcutting and erosion, which has been documented from as early as the 1960s. In 2010, the Shiawassee Conservation District received a grant from the Great Lakes Commission to address this erosion using modern techniques that are designed to lessen the erosive power of the water.
Rehabilitation of the State Road Drain was accomplished by incorporating characteristics of a stable channel, redirecting flows and stabilizing the channel bed using in-stream structures including cross vanes, vanes, riffle-pool sequences and channel relocation. Cross vanes and vanes are rock structures that are placed within the stream channel to redirect flow for the purpose of centralizing the water flow, providing grade control and stabilizing eroding stream banks.
Riffles, found throughout natural stream systems, are areas of fast moving water. Riffles are associated with pools, which are areas of slower moving water upstream and downstream of a riffle. Riffles and pools were constructed in this project to control extremely high velocities, establish grade and reduce bed and bank erosion. The result of installing the riffles and pools within the State Road Drain is improved channel stability that significantly reduces erosion rates, improves water quality and habitat, increases dissolved oxygen levels, reduces turbidity and cools water temperature. This, in turn, provides excellent habitat for aquatic organisms.
Channel relocation was conducted along reaches of the watercourse where the channel had meandered into highly erosive banks and caused severe bank erosion. The channel relocation involved creating a new channel away from the eroding bank. The newly created channel was designed using natural channel design concepts including proper channel width and depth and access to floodplain.
Pennington Farm Drainage did the construction work on this project and installed the vanes, cross vanes, riffle-pool sequences and channel relocation in the State Road Drain.
All of the techniques installed, working together, will reduce the highly erosive energy of the water previously causing erosion of the channel bed and banks. The result is the reduction of an estimated 414.5 tons of soil loss per year, which is equivalent to a reduction of 25 dump trucks-full of sediment annually dumping in the Shiawassee River.
Erosion and downcutting in the State Road
Drain were addressed using innovative
techniques including cross vanes, riffles
and pools, pictured here. This photo was
taken in Nov., 2012.
This project is part of the larger Shiawassee River Sediment Reduction Project, which is aimed at addressing the considerable sources of erosion in the watershed through innovative techniques and partnerships. Contributors to the State Road Drain Rehabilitation Project include the Natural Resources Conservation Service, Fitchbeck Thompson Carr & Huber and landowners in the drainage area. For more information on this project or the Shiawassee River Sediment Reduction Project, please contact the Shiawassee Conservation District.