DAM OVERTOPPING RESISTANCE AND BREACH PROCESSES RESEARCH

Authors: Hanson, Gregory; Temple, Darrel; Cook, Kevin

Submitted to: State Dam Safety Officials Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/13/1999
Publication Date: N/A
Citation: Hanson, G.J., Temple, D.M., Cook, K.R. 1999. Dam overtopping resistance and breach processes research. In: Dam Safety 1999. Proceedings of the Association State Dam Safety Officials, October 1999, St. Louis, MO. 7 p.

Interpretive Summary: Reservoirs that have been placed on the landscape have been of great benefit for flood control, water supply, recreation, sediment deposition, and aquatic ecosystems. Engineers designed these reservoirs for a specific design flood based on risk to people and property downstream of the reservoir. The design flood for many of these structures has changed because of people moving in downstream as well as changes in public policy In order to properly handle the new design flood, modifications to the reservoir are often required. This may involve increased reservoir storage or increased reservoir discharge. An inexpensive approach to increasing discharge that is being considered is allowing limited reservoir embankment overtopping in extreme flood events. Overtopping could potentially erode the embankment and release flood waters from the reservoir. Therefore, there is a need for improved physically based embankment overtopping and erosion models. Research is being conducted at the Agricultural Research Service's Plant Science and Water Conservation Research Laboratory in Stillwater, OK, related to embankment overtopping and erosion. New dam overtopping and erosion modeling tools from this research will provide better safety assessment of existing dams.

Technical Abstract: The benefits of reservoirs for flood control, water supply, recreation, sediment deposition, and aquatic ecosystems has resulted in thousands of dams being constructed. These dams were designed for a specific inflow design flood based on the risk to people and property downstream of the dam. People moving in downstream as well as changes in public policy have resulted in required changes in the inflow design flood. Changes in the inflow design flood often require modifications of the dam to increase spillway capacity and/or storage. One alternative to expensive modifications that is being considered is allowing limited embankment overtopping in extreme flood events as an acceptable operating procedure. Therefore, there is a need for improved physically based embankment dam overtopping and breach models. Research, related to embankment overtopping and embankment failure due to overtopping, described in this paper is being gconducted at the Agricultural Research Service's Plant Science and Water Conservation Research Laboratory in Stillwater, Oklahoma. This research has involved the construction of both indoor and outdoor models. The outdoor models include construction and testing of 5.5- to 10-ft embankments for overtopping and breach studies. Soil materials ranging from a unified soil classification of SM to CL are being tested in these experiments. There have also been indoor rigid boundary models constructed to examine discharge through the breach opening of a reservoir. New dam overtopping and breach modeling tools from this research can provide better safety assessment of existing dams.