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|Title:||Relationships of physical and biological characteristics of cutoff bends along the Tennessee-Tombigbee Waterway|
|Authors:||United States. Army. Corps of Engineers. Mobile District.|
Shields, F. Douglas.
Schaefer, Thomas E.
Gibson, Anthony C.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; EL-90-4.|
Abstract: Construction of the Tennessee-Tombigbee Waterway (TTW) involved construction of a navigation channel across the necks of 38 meander bends of the Tombigbee River, The cutoff bends, or bendways, constitute a valuable resource that the Corps of Engineers is committed to maintain. This study was conducted to provide a rational basis for refinement of the management strategy. Fish and water quality data collected over a semiannual basis over a 3-year period from 12 of the TTW bendways were compared with physical data from aerial photographs and annual hydrographic surveys of 13 of the bendways. To broaden the basis of study findings, similar data for three Upper Mississippi River side channels and 12 Lower Mississippi River floodplain lakes were also examined. Eight of the Lower Mississippi River sites had been sampled by other investigators in 1987. One of these lakes and four additional ones had been sampled in 1985 and in 1986. Important aquatic physical habitat factors for the TTW bendways included current velocity, bendway morphology, and water quality. During the period of this study, current velocities were negligibly small in all of the TTW bendways. Bendway morphology is directly related to the vertical location of the bendway channel relative to normal pool elevation. Bendways in the higher, upstream reaches of navigation lakes tended to be shallower and narrower than those in the middle or lower reaches. Bendways in the downstream portions of the lakes just upstream from the dams tended to resemble deep reservoir embayments. Based on Kulczynski Type I similarity analyses, fish community composition varied little among the TTW bendways. Electrofishing catch per unit effort and the average number of fish species per electrofishing transect varied inversely with depth and thus was greater for the upper pool bendways. Summer DO levels near the bottom of the water column were lower in the deeper bendways, and Secchi disk depths were higher. Biological differences among the Upper Mississippi River side channels and the Lower Mississippi river floodplain lakes were related primarily to the relative influence of the main channel rather than depth or shoreline development. However, fish diversity and standing stock reported from the 1987 investigation were inversely related to depth.
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