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Meander Bend Restoration in an Incised River

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  022238,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.10432) @2002
Authors:   J.A. Magner
Keywords:   River Restoration, Incised Channel, Point Bar, Geomorphic

Rahr Malting Company in negotiating their NPDES permit, piloted a point/nonpoint source pollutant trade with the Minnesota Pollution Control Agency. One objective included river restoration at an eroding bank/bluff. Geomorphic data was collected along a 200-m meander bend of the incised Rush River near Henderson Minnesota. The data was used to design and construct 10 J-hook rock vains tied to a 4-m wide floodplain bench along the outside bank/bluff. The practice decreases near bank shear stress by moving the thalweg away from the toe slope of the eroding bank/bluff. The floodplain bench provides velocity reduction for flows larger than the 1-to-2-yr-recurrence interval. The curled end of the J creates compressed accelerated flow into the thalweg to form a scour hole for fish habitat and increased pool channel cross-sectional area.

After, 2 back-to-back 5-yr flood events in April 2001, the toe slope of the bank/bluff remained stable. However, J-hook rock vains 7-10 sustained damage due to velocities in excess of 1.8 m/s. The damage was caused by inadequate point bar formation. The incised point bar was not reshaped to accommodate the necessary bankfull channel width through the meander bend. Several 1-m J-hook rocks were entrained and deposited 0.5-km downstream. Continuous on-site inspection is necessary when working with contractors unfamiliar with the geomorphic approach to river restoration.

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