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|Title:||Environmental effects of dikes and revetments on large riverine systems|
|Authors:||Iowa State University. Iowa Cooperative Fishery Research Unit.|
Iowa State University. Department of Animal Ecology.
Environmental and Water Quality Operational Studies (U.S.)
Sandheinrich, Mark B.
Atchison, Gary J.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Beginning in 1978, the Environmental and Water Quality Operational Studies (EWQOS) Work Units VA and VIIB were conducted by the Environmental Laboratory, US Army Engineer Waterways Experiment Station (WES), and other agencies contracted by WES to determine the impacts of navigation structures (dikes and revetments) on riverine habitats and biota. The rivers studied included the Lower Mississippi, Willamette, Arkansas, and Middle Missouri. A review of these studies, as well as other pertinent research, suggests that dikes and revetments have short-term and long-term effects on major riverine ecosystems. Short-term effects may be beneficial and include increases in aquatic habitat diversity and physical stability which, in turn, results in high densities and diversities of fish and macroinvertebrates within the main stem of the river. Dike fields are intermediate physically, chemically, and biologically to the main channel and backwaters of rivers. Dike fields often support the most diverse fish and macroinvertebrate community of any habitat within the river. But community composition is less stable than backwaters and is dependent upon river stage and water velocity. Moderate and slow-water areas within dike fields provide important spawning and nursery areas for many lotic species of fish within the modified river. Revetments of broken rock stabilize banks and provide additional hard substrate for colonization by dense populations of invertebrates. Interstitial spaces between rocks may provide areas of moderate flow for juvenile and forage fish. Long-term effects of river training structures may be detrimental to the biotic integrity of the river. Increased water velocity in the thalweg, as a result of the current being forced into the middle of the channel by dikes, results in riverbed degradation and dewatering of backwater areas during low flow. Stabilization of the channel prevents the river from meandering and forming new oxbow lakes, secondary channels, and backwater habitats. Deposition of silt in backwaters and on the downstream side of dikes results in the loss of these habitats in extreme cases. The result, as demonstrated in portions of the Missouri River, is a reduction in water-surface area; loss of islands, chutes, and backwater areas; and the constriction of the river to a single, narrow channel. On the Lower Mississippi River, these effects have not yet been defined.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Technical Report|
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