: Construction of the Tennessee-Tombigbee Waterway (TTW) involved construction of a navigation channel across the necks of 38 meander bends of the Tombigee 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 on 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. 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.

Large woody debris (LWD) removal (also called clearing and snagging) is a widely employed practice. The LWD is removed from small channels to increase conveyance (i.e., reducing the stage and duration of high frequency flooding) and from large channels to eliminate navigation hazards. Complete removal of LWD can have detrimental effects upon stream habitats. Thus, a balance between habitat considerations and channel conveyance is necessary. Selective removal of bank and near-channel floodplain vegetation and channel obstructions is a means of accomplishing this balance. The principal objective of this study was to investigate incremental effects of selective clearing and snagging on physical conditions and aquatic habitat in a sand bed river. The study was part of a larger program to develop techniques to quantify and predict incremental physical and biological effects of LWD removal. Long-term research objectives are to relate the densities and types of LWD formations in streams to specific biotic parameters, near-bank-full friction factor, and longitudinal dispersion as an indicator of the tendency a channel reach to trap and hold fine particulate matter. In this study, a simple method for quantifying LWD density and computing associated friction factors was developed and tested using data collected during a clearing andmore » snagging project on the South Fork Obion River in western Tennessee.« less