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Title: Design and development of bendway weirs for the Dogtooth Bend Reach, Mississippi River : hydraulic model investigation
Authors: United States. Army. Corps of Engineers. St. Louis District.
Derrick, David L.
Pokrefke, Thomas J.
Boyd, M. B. (Marden B.)
Crutchfield, James P.
Henderson, Raymond R.
Keywords: Bendway weirs
Mississippi River
Navigation channels
Channel improvement
Dikes (training structures)
Sills (training structures)
Weirs (training structures)
Diversion weirs
Movable-bed model
Hydraulic models
River training structures
Dogtooth Bend Reach, Mississippi River
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; HL-94-10.
Description: Technical Report
Abstract: This investigation is one of a series of model studies used to determine the effectiveness of various dike and bendway weir systems proposed for the improvement of several troublesome reaches on the Mississippi River. This report describes and gives results of test concerned with the development of plans for the improvement of the Dogtooth Bend reach of the middle Mississippi River, located 20 miles above the confluence of the Ohio and Mississippi Rivers. A movable-bed model reproducing approximately 19.4 miles of the Mississippi River (horizontal scale 1:400, vertical scale 1:100) and using granulated coal as the bed material was employed to develop plans that would improve and stabilize the navigation channel through the reach and eliminate or reduce the need for maintenance dredging. The goals of this study were to improve current flow patterns and widen the navigation channel in Dogtooth and Price's Landing Bends and in the crossings immediately downstream of both bends. Currents concentrating on the outside bank of a number of bends have caused serious problems for barge traffic and major damage to bank stabilization and protection structures. During a high-water event in 19S3 the bank line at Dry Bayou (mile 23.3) failed, allowing the river to flow overland for approximately 5 miles. Damage to bank protection structures and farmland was significant. Typically a narrow navigation channel through a bend forces tows to flank (a series of start and stop maneuvers) during low and medium stages, slowing the maneuvering tow and delaying any upstream or downstream traffic waiting for the flanking tow to clear the bend. The economic impact of such delays on the Mississippi River between St. Louis, MO, and Cairo, IL, has been estimated at between 13 and 26 million dollars annually, depending on river conditions. Also, winter ice jams at the bends have caused traffic bottlenecks, the costs of which have not been ascertained. Dredging in the bends and crossings to improve navigation has also been a major expense for the Corps. Annual dredging costs on the open river section of the middle Mississippi River (miles 198.7 to 0.0) alone average between 4 and 6 million dollars in the bends, with another 5 to 6 million dollars spent on the crossings. Model test results indicate that construction of 2 series of upstream-angled underwater sills (bendway weirs) within the navigation channel of a bendway results in the following improvements : the navigation channel through the bendway is widened, deposition occurs at the toe of the revetment on the outside of the bend stabilizing the bank, surface water velocities are more uniform across any cross section, flow patterns in the bends are generally parallel with the banks and do not concentrate on the outside bank of the bend , the navigation channel in the crossing downstream of the bend is both deeper and wider, and the navigation channel through the bend and downstream crossing is better aligned. The use of bendway weirs could also result in several environmental benefits. The habitat of the least tern (a federally protected endangered sea bird species whose territory includes the bendway point bars) should not be affected or disturbed. The navigation channel is reshaped from an inverted triangle into a wider, shallower trapezoid. This new channel shape results in an improved and expanded usable aquatic habitat area, which, with time, should translate into increased densities of aquatic life. The diversity of aquatic life might also be increased. Finally, the improved navigation channel should result in a marked decrease in the amount of channel maintenance dredging performed, resulting in less dredged material to be disposed of. 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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