|Shields Jr, Fletcher|
Submitted to: River Channel Restoration
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/1996
Publication Date: N/A
Interpretive Summary: When stream channels without stream bed controls cut down through the landscape, they provide a continuing source of tons of sediment every year. This channel incision is a major problem in the hill lands of the Mississippi River valley. A federal interagency project (Demonstration Erosion Control Project in the Yazoo Basin) begun in 1984 in Mississippi has demonstrated many channel stability measures which can help solve this problem. One of the popular technology transfer aspects of the project has been positive results of ecological studies which used channel stability construction efforts to generate better quality aquatic and terrestrial habitat at little or no extra cost. Because of the demonstration nature of the project state and federal agencies that deal with stream stability or habitat improvement issues can visit works in place and make immediate use of positive results and lessons learned.
Technical Abstract: Channel incision, particularly devastating in watersheds with no bed controls, separates a stream from its floodplain, destroys arable land, and degrades environmental resources. A demonstration project dealing with channel erosion was begun in 1984 in the loess hill lands of northwestern Mississippi, USA. The project objective centered on developing stabilization/rehabilitation technology in 15 watersheds (1 to 1,590 km**2) characterized by erosion and sedimentation associated with channel incision. Suspended sediment yields averaged about 1,000 t km**-2-yr**-2. Stream channels were typically straight due to past (ca. 1880 to 1970) channelization, enlarged by erosion, and have little woody debris, pool habitat, or stable substrate. Structural measures were selected on the basis of specific site needs within the scope of total watershed planning and were designed on the basis of geotechnical and hydraulic parameters. Common measures included field-scale grade control pipes, stream grade controls, bank protection, and floodwater-retarding reservoirs. Channel cleanout and levees were less common. Aquatic habitat studies at >100 sites showed that major needs included greater water depth and improved habitat stability. Based on water depth and increases in number of species and biomass, grade control structure energy-dissipation pools, stone spur dikes, and V-shaped weirs improved in-stream habitat. Field-scale grade controls and sediment retention ponds created wetland and open water habitats for all classes of vertebrates. Success of woody vegetation plantings [primarily native willow (*Salix* spp.)] varied with site.