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United States Department of Agriculture

Agricultural Research Service

Dam Breach Processes
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Thousands of dams built in the U.S. and around the world have a potential to be overtopped by flood flows. It is therefore necessary to understand the mechanics of embankment erosion due to overtopping in order to evaluate the potential erosion damage to an embankment and the safety risk that overtopping presents. Research is presently underway at the USDA-ARS within the Research Hydraulic Engineering Unit to evaluate the performance of vegetated earth embankments subjected to overtopping. 


The three-phase earth spillway erosion technology developed for the Natural  Resources Conservation Service SITES software forms the point of beginning for this effort.  Initial results of full scale overtopping tests suggest that it may be possible to extend this technology to the steeper slopes of earth embankments. The goal of the research effort is to predict the amount of allowable embankment overtopping that can be experienced without significant damage, the extent of overtopping required to breach a specific embankment, and the rate of breach development, or the breach hydrograph that may result from the breach.

Predicting Erosion for Dam Safety

ARS research is providing the knowledge and tools needed to better understand and predict the performance of earth dams and spillways subjected hydraulic attack during major floods and incidents.  The aging of the nation's dams with associated filling of sediment pools and development in the watersheds increase the likelihood that vegetated auxiliary spillways will experience major flows and the possibility that earth dams may be overtopped during major floods.  During 2009, ARS scientists continued to study and quantify the processes by which embankments resist hydraulic attack.  This work has led to the development of an alpha test version of WINdows Dam Analysis Modules (WINDAMb) application software for use by engineers in the evaluation of the breach potential of existing dams.  When these tools are developed to the point of field application, they will assist engineers in determining the best use of limited resources in maintaining public safety.  The ARS research effort also includes cooperation with the NRCS, the US Army Corps of Engineers, Universities, and the international community.  The cooperative efforts of the ARS and NRCS also resulted in the updating of the SITES software used by NRCS in dam and spillway design and analysis.  SITES 2005 has additional features for broader application and ease of use.


During 2009, additional progress has been made on research associated with internal erosion and breach of earthen embankments.  In addition to overtopping, internal erosion is one of the primary ways that earthen embankments fail.  This research has involved large scale model tests, characterization of soil materials for use in predicting internal erosion, and development of prediction equations for modeling internal erosion processes. 

For additional information contact our office.


Watershed Flood Control Fact Sheet




Last Modified: 8/13/2016
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