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Title: A study of cutoff bendways on the Tombigbee River
Authors: Environmental and Water Quality Operational Studies (U.S.)
Pennington, C. H.
Baker, John A.
Howell, Fred G.
Bond, Carolyn L.
Keywords: Channel bends
Environmental analysis
Environmental aspects
Environmental effects
Tombigbee River
River cutoffs
Water quality
Aquatic ecology
Tombigbee River
Publisher: Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: Biological and physical data were collected from four bendways within the river portion of the Tennessee-Tombigbee Waterway (TTW) from Columbus, Mississippi, to Demopolis, Alabama : Rattlesnake Bend, Cooks Bend, Big Creek Bendway, and Hairston Bend. During this study, the four bendways had not all been cut off and had been impounded for varying lengths of time. At the completion of the TTW project, all four of the bendways will be severed from the main navigation channel. Four distinct areas within each bendway were compared: above the bendway; within the bendway; below the bend way; and within the cut. Sampling was conducted from January 1979 to September 1980 to coincide with four different river stage/water temperature regimes: late fall-moderate flow/decreasing water temperature; winter-high flow/low temperature; spring-high flow/rising temperatures; and summer-low flow/warm water temperatures with increased probability of thermal stratification. Data were collected for numerous physical and water quality parameters, phytoplankton and chlorophyll, benthic macroinvertebrates, and fishes. During early September 1980 a mollusk and aquatic macrophyte survey was conducted at all four bendways. The U. S. Army Engineer District, Mobile, provided data on substrate composition and bottom profiles. Sediment analysis and bottom profiles indicated that the substrate composition of some of the bendways is changing. Overall, the substrate of the study area is changing from a sand-gravel-fines mixture to one of predominantly sand and fines. Areas of some bendways, in particular the upper areas, were accumulating sediments. At big Creek Bendway, this accumulation completely blocked water exchange between the river and the within-bendway areas. Few significant differences in water quality were documented for either within individual bendways or among the four bendways. Only at Big Creek Bendway were consistent differences found between within-bendway samples and river samples. Phytoplankton composition and chlorophyll concentrations showed only small differences among bendways. Aquatic macrophytes were scattered and uncommon in the four bendways. Water-willow (Justicia sp.) was most commonly encountered, particularly in Rattlesnake Bend where numerous small beds were found. Based upon total collections, a consistent family assemblage of macroinvertebrates characterized the four bendways. Although 60 family-level taxa were collected, nine families of macroinvertebrates accounted for between 93.5 and 97.2 percent of the benthos. The importance of these families varied among bendways and appeared to reflect differences in physical bendway conditions, particularly substrate type and current velocities. Similarity indices indicated that the benthic communities of the four bendways were qualitatively very similar; they became less similar with increasing river-mile separation. Quantitatively, differences appeared to be due to shifts in dominance of the nine most common families associated with date of bendway cutoff. Eighteen species of Unionid mollusks, plus the Asian clam Corbicula, were collected during the surveys. Nearly all the specimens were found at Big Creek Bendway; none were collected at Hairston Bend. With the exception of three species of Pleurobema, no unusual or uncommon mollusk species were found. Based on overall ichthyofaunas, two groups of bendways were delineated that corresponded to impoundment and riverine habitats. Rattlesnake Bend and Cooks Bend were located in lower pool sections, where impoundment conditions prevailed, and their ichthyofaunas were dominated by clupeids (shad) and centrarchids (sunfishes, crappies, and basses). Hairston Bend, essentially a riverine reach during this study, was dominated by cyprinids (minnows), ictalurids (catfishes), and catostomids (suckers). Big Creek Bendway, unique in having both riverine and lacustrine habitats, was faunistically most similar to Hairston Bend, but also showed moderate similarities to the other bendways. The number of species collected at a bendway and the mean species diversity decreased from Hairston Bend downstream to Rattlesnake Bend. The mean numerical catch per unit of effort C/f and the mean number of species per station were considerably higher at Big Creek Bendway and Cooks Bend than at Hairston Bend and Rattlesnake Bend. The mean total weight of fish per unit of effort C/y was more similar among bendways. The C/f, C/y, and means number of species per station differed among areas within individual bendways. NOTE: This file is large. Allow your browser several minutes to download the file.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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