OHD/HL/HSMB - Hydraulics: Dam Break

Develop Improved Guidance for Dam Break Forecasting

Although dam failures are infrequent, the impacts can be catastrophic. The National Weather Service (NWS) must issue accurate and timely forecasts of flood waves resulting from dam failures to protect lives and property. Although already an important part of the NWS mission, accurate dam break forecasts will become increasingly important during the next 25 years. In 2020, approximately 80 percent of dams in the United States will be more than 50 years old (Canino and Taylor, 2004; Koehler, 2008 )

Dam failures can be sudden events and the resulting flood waves travel rapidly downstream; therefore, forecasters need pre-calculated scenarios in many situations. However, it may not be possible to pre-calculate all important scenarios, and for this reason it will be beneficial to re-run models during events using real-time information (particularly with information about how quickly the dam is failing and the current water level). One of the biggest engineering challenges is predicting the time it will take a dam to fail, and this time to failure has a major influence on the flood characteristics at downstream points.

In this project, we reviewed modeling procedures available at NWS River Forecast Centers to develop quantitative forecasts for dam break floods, e.g. peak flow, peak stage, and peak time at downstream locations. The primary goal was not develop new models, but to provide River Forecast Centers better documentation on how and when to use existing models and modeling tools. An additional outcome was the development of a new GIS-based tool to develop inputs for the Simplified Dam Break Model (Whetmore et al., 1991):

REFERENCES

Canino, M., Taylor, M., (2004). Aging Dams Threaten U.S. Water Supply Systems, AWRA Annual Meeting Conference Proceedings.

Koehler, R., (2008). Dams and Dam Failure - Module 1: Terminology and Open Channel Hydraulics, https://www.meted.ucar.edu/training_module.php?id=469

Whetmore, J.N., Fread, D.L., Lewis, J.M., Wiele, S.M., (1991). The NWS Simplified Dam-break Flood Forecasting Model, 47 pp.