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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #133520
Title: CHANNEL RESPONSES AND MANAGEMENT STRATEGIES IN DISTURBED CHANNELS: A NUMERICAL SIMULATION APPROACH

Author
item THOMAS, ROBERT - UNIV. OF MISSISSIPPI
item LANGENDOEN, EDDY - UNIV. OF MISSISSIPPI
item Bingner, Ronald - Ron
item Simon, Andrew

Submitted to: American Society of Civil Engineers Water Resources Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/19/2002
Publication Date: 5/19/2002
Citation: Thomas, R., Langendoen, E., Bingner, R.L., Simon, A. 2002. Channel responses and management strategies in disturbed channels: a numerical simulation approach [CD-ROM]. Proceedings American Society of Civil Engineers Water Resources Planning and Management, Roanoke, VA, May 19-22, 2002. 10 pp.

Interpretive Summary: The streams of the Yalobusha River watershed were extensively dredged and reconstructed during the 1960s. The newly altered system experienced channel degradation, increasing bank heights above stable conditions, causing bank failures and the addition of vegetation and sediment to the channels. The amount of sediment added to the river basin due to bank failures and bed degradation alone has been estimated to be 833,000 tonnes/yr, while the input of vegetation due to bank failure at 11 critical points in the watershed has been estimated to be around 100 trees/yr. This has caused a large logjam to form at the downstream end of the channel works. This debris 'plug' has caused increased water levels and flood frequencies in the vicinity of Calhoun City, 5 km upstream. The U.S. Army Corps of Engineers have identified a number of strategies to improve conditions including plug removal, numerous structures to prevent bed degradation following plug removal, and flood-retarding structures. The one-dimensional, unsteady, gradually varying open channel flow model, CONCEPTS (CONservational Channel Evolution and Pollutant Transport System) is being used to model channel responses to the 1960s channel works, including bed degradation, bank failures and hence sediment inputs and loads from 1968 to 1997. CONCEPTS has been shown to accurately depict in-channel and bank processes and hence can correctly predict the effects of channelization together with future rehabilitation measures.

Technical Abstract: The Yalobusha River watershed underwent extensive channelization and channel repositioning during the 1960s. The newly channelized system experienced channel degradation, rejuvenating tributaries and increasing bank heights above stable conditions, causing bank failures and the addition of vegetation and sediment to the channels. The amount of sediment added to the river basin due to bank failures and bed degradation alone has been estimated to be 833,000 tonnes/yr, while the input of vegetation due to bank failure in the vicinity of major knickpoints has been estimated to be around 100 trees/yr. This has promoted the development of a large logjam at the downstream terminus of channelization works. The debris 'plug' has caused increased stages and flood frequencies in the vicinity of Calhoun City, 5 km upstream. The U.S. Army Corps of Engineers have identified a number of remediation strategies including plug removal, numerous grade-control structures to arrest headward migration of knickpoints following plug removal, and flood-retarding structures. The one-dimensional, unsteady, gradually varying open channel flow model, CONCEPTS (CONservational Channel Evolution and Pollutant Transport System) is being used to model channel responses to channelization, including bed degradation, bank failures and hence sediment inputs and loads from 1968 to 1997. CONCEPTS has been shown to accurately depict in-channel and bank processes and hence can correctly predict the effects of channelization together with future rehabilitation measures.