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Title: Comparing process-based breach models for earthen embankments subjected to internal erosion

Author
item Tejral, Ronald
item Hunt, Sherry

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/20/2015
Publication Date: 4/21/2015
Citation: Tejral, R.D., Hunt, S.L. 2015. Comparing process-based breach models for earthen embankments subjected to internal erosion. Proceedings of the Joint Federal Interagency Sedimentation and Hydrologic Modeling Conference, April 19-23, 2015, Reno, Nevada. 10 p. Available: http://acwi.gov/sos/pubs/3rdJFIC/index.html.

Interpretive Summary:

Technical Abstract: Predicting the potential flooding from a dam site requires prediction of outflow resulting from breach. Conservative estimates from the assumption of instantaneous breach or from an upper envelope of historical cases are readily computed, but these estimates do not reflect the properties of a specific dam. If it is desired to understand the effects of soil materials, embankment construction, and reservoir characteristics, a process-based model is needed. WinDAM C is the most recent module of the dam breach software under development by USDA-NRCS in cooperation with USDA-ARS and Kansas State University. It builds on the functionality of previous WinDAM releases (evaluation of embankment surface protection, breach by overtopping, and integrity of auxiliary spillways) by adding the ability to evaluate internal erosion. A process-based model of this type provides an additional tool for the engineer to evaluate the potential impact of site-specific characteristics including erosion process, embankment materials, reservoir storage, and embankment geometry. In addition, this tool may aid in the development of flood warning systems, emergency action plans, and prioritizing dams for rehabilitation. In this study, results of WinDAM C are compared and contrasted to those obtained using BREACH. A set of hypothetical, synthetic dams was used to represent the range of USDA Small Watershed Structures by varying height and reservoir volume augmented by three variations of detachment/transport rate. Outcomes of historical failure cases and physical model studies were compared to the synthetic set. The work suggests that WinDAM is predicting in the correct order of magnitude and exhibiting appropriate sensitivity to material parameters.