Skip to main content
ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #251439

Title: Assessing post-dam removal sediment dynamics using the CONCEPTS computer model

item Langendoen, Eddy

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/20/2010
Publication Date: 6/29/2010
Citation: Langendoen, E.J. 2010. Assessing post-dam removal sediment dynamics using the CONCEPTS computer model. In: Proceedings of the Federal Interagency Sedimentation Conference Proceedings. 2010. June 27-July 1, 2010, Las Vegas, NV. 12 pp. CD-ROM.

Interpretive Summary: Across the United States more than a thousand dams have been removed or are planned to be removed within the near future, often to improve in-stream habitat or due to decommissioning. Removal of a dam may cause significant erosion of the sediment stored within the former reservoir. Commonly a channel forms within the reservoir. The depth and width of the new channel are largely controlled by the rate at which the dam is removed and the sediment characteristics of the reservoir deposit. Scientists at the U.S. Department of Agriculture-Agricultural Research Service-National Sedimentation Laboratory have developed the channel evolution computer model CONCEPTS to predict similar channel adjustment processes in agricultural landscapes. New features were added to CONCEPTS to assess the effects of dam removal drawdown scenarios and the resulting changes in reservoir sediment erosion characteristics on channel forming processes. Application of the enhanced model to dam removal case studies on the Kalamazoo River, Michigan and the Klamath River, California showed excellent model agreement with: (1) conceptual models of upstream channel evolution within the reservoir, and (2) observations of elevated sediment transport processes downstream of the dam. CONCEPTS can be used by federal and state agencies, such as the US Geological Survey, the US Bureau of Reclamation, the US Corps of Engineers, the Natural Resources Conservation Service and the US Environmental Protection Agency, or private industry to assess the downstream impact of dam removal and duration of elevated sediment concentrations caused by upstream channel evolution.

Technical Abstract: Dam removal will impact stream morphology not just locally, but both far upstream and downstream. There is a critical need for tools to predict the rates, magnitudes, and mechanisms by which sediment is removed from a reservoir following dam removal, as well as for tools to predict where this sediment will be deposited downstream and how it will impact downstream channel morphology. Channel forming processes upstream of the dam are similar to those of channelized or incised streams. The US Department of Agriculture, Agricultural Research Service has developed the channel evolution computer model CONCEPTS to simulate the evolution of such channelized streams. CONCEPTS is therefore suitable to evaluate post-dam removal sediment dynamics. Further, the model contains features specific to dam removal studies, such as progressive lowering of the water surface elevation in case of phased dam removal and the consequent effects of dewatering of the stream bank/reservoir materials on bank material shear-strength. Application of CONCEPTS to evaluate dam removal consequences on the Kalamazoo River, Michigan, and the Klamath River, California, demonstrate the model’s performance.