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Title: RESEARCH ACTIVITIES ON THE EROSION MECHANICS OF OVERTOPPED EMBANKMENT DAMS

Author
item Hanson, Gregory
item MORRIS, MARK - HR-WALLINGTON, UK
item VASKINN, KJETIL - SWECO, NORWAY
item Temple, Darrel
item HASSAN, MOHAMED - HR-WALLINGFORD, UK
item Hunt, Sherry

Submitted to: The Journal of Dam Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2005
Publication Date: 5/1/2005
Citation: Hanson, G.J., Morris, M., Vaskinn, K., Temple, D.M., Hassan, M., Hunt, S. 2005. Research activities on the erosion mechanics of overtopped embankment dams. Journal of Dam Safety. 3(1):4-15.

Interpretive Summary: The asset value of dams and flood defense structures in the US, EU, and around the world amounts to billions of dollars. Many dams are located close to centers of population and industry and the consequences of failure of these structures include the risk of loss of both life and property. Erosion as a result of overtopping during flood events has been identified as one of the key causes of embankment dam failure. This report presents a discussion of small and prototype-scale research experiments that have recently been, or are being, conducted in the US, UK, and Norway on earthen embankment overtopping. The objective of this research is to advance the scientific knowledge and understanding of breaching by: 1) evaluating erosion processes; 2) determining breach erosion rates; and 3) collecting data for breach model development and verification.

Technical Abstract: The asset value of dams and flood defense structures in the US, EU, and around the world amounts to billions of dollars. Many dams are located close to centers of population and industry and the consequences of failure of these structures include the risk of both loss of life and property. Erosion as a result of overtopping during flood events has been identified as one of the key causes of embankment dam failure. This report presents a discussion of small-scale and prototype research experiments that have recently been, or are being, conducted in the US, UK, and Norway on earthen embankment overtopping. The tests have been conducted on embankments varying in height from 0.6-m to 6-m and from sandy to clay type materials. The objective of this research is to advance the scientific knowledge and understanding of embankment breaching. Observations and data recorded during these overtopping tests led to a four-stage description of the embankment breach process. In addition to the observed stages of the embankment breach process observations from these tests also include: 1) Vegetation on the embankment can play a major role in the embankments resistance to erosion; 2)Vertical or nearly vertical sidewalls during erosion and breach widening in all test cases; 3) Formation of an arch-type weir during breach formation; 4) Breach initiation time can be quite lengthy and often greater than breach formation time; and 5) Type and placement of embankment materials has a significant impact on the rate of embankment breach and resulting discharge. There is still much work to be conducted to integrate the research studies described in this paper. Effective integration of this work will avoid duplication of research effort and allow ideas and concepts from a wider range of sources to be considered.