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Title: PHYSICAL MODELING OF OVERTOPPING EROSION AND BREACH FORMATION OF COHESIVE EMBANKMENT

Author
item Hanson, Gregory
item Cook, Kevin
item Hunt, Sherry

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2005
Publication Date: 11/1/2005
Citation: Hanson, G.J., Cook, K.R., Hunt, S. 2005. Physical modeling of overtopping erosion and breach formation of cohesive embankment. Transactions of the ASABE 48(5):1783-1794.

Interpretive Summary: There are numerous earthen dams across the landscape, which are used for water supplies, flood control, recreation, etc. There is research being conducted by the USDA-ARS to develop computer models to predict what would happen if flood waters were to go over the top of these structures. Seven large-scale outdoor laboratory tests were conducted to measure the limits of these structures and erosion rates when water goes over the top. Erosion rates were strongly related to soil properties such as compaction water content, soil strength, and erodibility. The soil properties were related to erosion equation parameters that include the rate of erosion and water flow properties in this environment. The measured soil properties of erodibility and strength were observed to be promising for the development of physical models to predict embankment erosion and breach due to overtopping.

Technical Abstract: There are a number of recognized technology advancement needs associated with watershed structure re-evaluation and rehabilitation. One of those needs, addressed by embankment breach research, is technology for predicting performance during extreme events. Evaluation of the relationship of headcut migration and erosion widening rates during overtopping and breaching tests on large-scale models to measured hydraulic parameters and soil properties are described in this paper. Seven large-scale embankments overtopping tests have been conducted on embankments 2.3 m and 1.5 m high. Two of the embankments had three homogeneous test sections and one embankment had one wide homogeneous test section. The embankments had 3H:1V slopes on both the upstream and downstream sides. Three soils were tested, two non-plastic SM silty sand materials and a CL lean clay. The primary erosion processes observed were headcut migration and erosion widening. The rates of the erosion processes were observed to vary by several orders of magnitude and were observed to be strongly dependent on the soil material properties such as compaction water content, soil strength, and erodibility. The measured soil properties of erodibility and strength are promising for the development of physical models to predict embankment overtopping erosion and breach.