NWS Simplified Dam-Break Flood Forecasting Model   [open pdf - 2MB]

"A simplified model for predicting the downstream flooding produced by a dam failure is presented. This model has been developed to aid flash flood hydrologists who, because warning response time is short or adequate computing facilities are not available, are unable to utilize the NHS Dam-Break Flood Forecasting Model. Using only a hand-held calculator and the dimensionless graphs presented in this paper, the hydrologist may within minutes produce forecasts of the dam-break floodwave peak stages, discharges, and travel times. […]The ability of this model to predict the extent and timing of downstream inundation is tested with good results using data obtained during the dam-break floods produced by the failures of Teton Dam and the Buffalo Creek coal-waste dam. Prediction accuracy and the time required to use the model are examined for each application. A step-by-step example application is also presented. Advising the public of downstream flooding during a dam failure emergency is the responsibility of the National Weather Service (NWS). To aid NWS flash flood hydrologists in forecasting the inundation resulting from dam-failures, the numerical DAMBRK Model (Fread 1977, 1980) was developed for use with high-speed computers to model the outflow hydrograph produced by a time-dependent, partial dam breach and route this hydrograph downstream using the complete onedimensional unsteady flow equations while accounting for the effects of downstream dams, bridges, and off-channel storage. However, in some situations the use of the DAMBRK Model may be precluded because warning response-time is short or adequate computing facilities are not available. To alleviate this potential problem and to improve upon the accuracy and versatility of existing simplified dam breach modelling procedures (Saakas and Strelkoff, 1973; McQuivey and Keefer, 1975; Snyder, 1977; and SCS, 1979), the NWS has developed the Simplified Dam-Break (SMPDBK) Flood Forecasting Model. Employing only a handheld calculator and dimensionless graphs, the user may within minutes produce forecasts of the dam-break floodwave peak discharges, stages, and travel times. It should be noted here however, that the use of the NWS SMPDBK Model is not limited to NWS flash flood hydrologists. Planners, designers, civil defense officials, and consulting engineers who are concerned with the potential effects of a dam failure and who have limited time, resources, data, computer facilities, and/or experience with unsteady flow models may also wish to employ the model to delineate the areas facing danger in a dam-break emergency."

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