PRACTICAL CONSIDERATIONS IN MODELING EARTH DAM OVERTOPPING AND BREACH

Authors: Temple, Darrel; Hanson, Gregory; Hunt, Sherry

Submitted to: International Hydro-Science & Engineering International Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2004
Publication Date: 6/1/2004
Citation: Temple, D.M., Hanson, G.J., Hunt, S.L. 2004. Practical considerations in modeling earth dam overtopping and breach. In: Proceedings of the 6th International Conference on Hydro-Science and -Engineering. Advances in Hydro-Science and Engineering, May 30 - June 4, 2004, Brisbane, Australia. 2004 CDROM.

Interpretive Summary: Aging of the nation's flood control infrastructure results in an increased need for improved mathematical and computer models describing the breach process for embankment dams subjected to overtopping during extreme flood flows. Observation of overtopped embankments both in the field and during large-scale laboratory tests indicate that it is possible to approach the development of a model through component actions for the purpose of simplifying the mathematical description of the complex interaction of the flow with the eroding boundary. The sequential components describing the progress of the breach are identified through preliminary evaluation of available data as: 1) local destruction of the vegetal cover, if any, and development of concentrated flow on the embankment face, 2) concentrated flow erosion leading to the development of a headcut capable of advancing upstream through the embankment, 3) upstream advance and deepening of the headcut as it progresses into the reservoir, and 4) removal of the upstream face of the embankment after the headcut becomes submerged following entry into the reservoir. The relations describing outflow through the breach also vary with the phase of the breach process, and outflow hydrograph prediction requires description of the widening of the eroding area during each phase of the breach process and of the continued widening during reservoir drawdown. Research focusing on development and integration of the model components is underway. This research builds on existing models of earth spillway erosion. This report discusses the overall breach process and the progress being made toward development of a computational tool for engineering application.

Technical Abstract: Aging of the nation's flood control infrastructure results in an increased need for improved mathematical and computer models describing the breach process for embankment dams subjected to overtopping during extreme flood flows. Observation of overtopped embankments both in the field and during large-scale laboratory tests indicate that it is possible to approach the development of a model through component actions for the purpose of simplifying the mathematical description of the complex interaction of the flow with the eroding boundary. The sequential components describing the progress of the breach are identified through preliminary evaluation of available data as: 1) local destruction of the vegetal cover, if any, and development of concentrated flow on the embankment face, 2) concentrated flow erosion leading to the development of a headcut capable of advancing upstream through the embankment, 3) upstream advance and deepening of the headcut as it progresses into the reservoir, and 4) removal of the upstream face of the embankment after the headcut becomes submerged following entry into the reservoir. The relations describing outflow through the breach also vary with the phase of the breach process, and outflow hydrograph prediction requires description of the widening of the eroding area during each phase of the breach process and of the continued widening during reservoir drawdown. Research focusing on development and integration of the model components is underway. This research builds on existing models of earth spillway erosion. This report discusses the overall breach process and the progress being made toward development of a computational tool for engineering application.