LIMITED OVERTOPPING, EMBANKMENT BREACH, AND DISCHARGE

Authors: Temple, Darrel; Hanson, Gregory

Submitted to: Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/23/2002
Publication Date: 6/1/2002
Citation: Temple, D.M., Hanson, G.J. 2002. Limited overtopping, embankment breach, and discharge. Report on workshop on issues, resolutions, and research needs related to dam failure analysis. Oklahoma City, OK, June 26-28th, 2001. 8 p.

Interpretive Summary: Over 10,000 flood control reservoirs constructed with the assistance of the USDA represents a $14 billion dollar investment and provides almost $1 billion in benefits each year. Sixty-two percent of these 10,000 structures will reach age 50 by 2020. As these structures age, additional trapped sediment may reduce the flood control capacity of the reservoir, population increases, and changes in land use in the upstream watershed may result in increased runoff, and encroachment on the downstream channels may result in structures that were designed to protect agricultural land now being depended upon to protect lives and homes. In many instances, dam safety regulatory requirements have also changed since the original construction as a result of federal legislation and/or state laws. Because of this, public safety requires that this aging infrastructure be re-evaluated and, in some cases, rehabilitated. A key aspect of this re-evaluation is prediction of the performance of existing hydraulic structures and channels during extreme flood events that may exceed original design conditions. This includes prediction of allowable overtopping, rate of embankment breach and failure, and resulting discharge into the downstream floodplain. Therefore, the Hydraulic Engineering Research Unit of the ARS Plant Science and Water Conservation Research Laboratory in Stillwater, OK, is conducting research, described in this paper, to address dam safety concerns associated with rehabilitation of these structures.

Technical Abstract: Over 10,000 flood control reservoirs constructed with the assistance of the USDA provide almost $1 billion in benefits each year. Sixty-two percent of these 10,000 structures will reach age 50 by 2020. As these structures age, additional trapped sediment may reduce the flood control capacity of the reservoir, population increases, and changes in land use in the upstream watershed may result in increased runoff, and encroachment on the downstream channels may result in structures that were designed to protect agricultural land now being depended upon to protect lives and homes. In many instances, dam safety regulatory requirements have also changed since the original construction as a result of federal legislation and/or state laws. Because of this, public safety requires that this aging infrastructure be re-evaluated and, in some cases, rehabilitated. A key aspect of this re-evaluation is prediction of the performance of existing hydraulic structures and channels during extreme flood events that may exceed original design conditions. This includes prediction of allowable overtopping, rate of embankment breach and failure, and resulting discharge into the downstream floodplain. Therefore, the Hydraulic Engineering Research Unit of the ARS Plant Science and Water Conservation Research Laboratory in Stillwater, OK, is conducting research, described in this paper, to address dam safety concerns associated with rehabilitation of these structures.