Great Plains Studies, Center for

 

Date of this Version

Fall 2012

Citation

Great Plains Research 22 (Fall 2012):147-61

Comments

© 2012 Copyright by the Center for Great Plains Studies, University of Nebrosko-Lincoln

Abstract

In 1996 a side channel was excavated on 629 hectares of former agricultural land at Upper Hamburg Bend on the Missouri River in Otoe County, NE. This was the first side channel constructed on the Missouri River in an attempt to restore lost aquatic habitat. The initial design was for an approximately 4,200 m long side channel to be constructed with a 3 m bottom width. Development ofthe site was to be dependent on flows diverted from the main channel of the river with a final projected top width of 61 m. The side channel was completed in the spring, and shortly thereafter the site was subjected to a series of flood events. The side channel has been subjected to periods of both high and low water since opening. We documented physical changes at the site with the aid of aerial photography, acoustic Doppler current profiler (ADCP) surveys, and topographic surveys. By 2010 the side channel was 4,342 m long with a mean top width of89.5 m. Channel development has occurred during periods of high and low water. ADCP surveys established that mean depths and velocities have increased since 2001. An increase in the amount of discharge through the side channel since 2001 has resulted in the loss of some of the shallower and lower velocity habitats. Modifications to the site may be necessary to reverse this loss of shallow, slow water habitat that the side channel was designed to provide. Although new off-channel aquatic habitat has been created, channel development has been impacted by the presence of rock control structures throughout the site. Reducing the number of control structures to the minimum necessary to prohibit the side channel from impacting adjacent properties may allow the continued restoration of lost alluvial processes through the ongoing process of bend development and migration.