Risk-benefit assessment of dam early warning systems

Simply stated, flood warnings are issued to reduce risk to life and property. If there is sufficient lead time, more aggressive activities can be accomplished to reduce property damage, such as relocating contents of residences, businesses and municipalities; not to mention the ability to initiate flood fighting measures. More importantly, sufficient warning can enable persons to be evacuated when faced with such impending danger. Each action taken as the result of advanced planning and increased warning time has direct outcomes in terms of derived benefits. The U.S. Army Corps of Engineers (COE) provides high quality and efficient support to the Nation's security and well being within a broad range of water resource related projects. To support the flood damage reduction mission, the COE, Huntington District owns and operates a complete gauging system for the purpose of making operational decisions on the 35 reservoirs within the District's boundaries. In addition, the Huntington District has developed and implemented several basin-wide flood warning systems (FWS), which share data with other Federal agencies as well as non-Federal entities and local communities. As a catalyst in accomplishing the goal of the flood control mission, Huntington District is responsible for operation and maintenance of approximately 260 gages over a 45,000 square mile area. Many of the other COE Districts share similar responsibilities within their boundaries. Ongoing inspection, maintenance and replacement are essential to provide a reliable system. Risk based analysis techniques provide little guidance on the extent of risk reduction that should be attributed to providing a FWS. Justification of the systems from a benefit cost analysis is fairly straight forward, but guidance is not available for the application of risk reduction attributed to the FWS associated with a catastrophic failure from a dam breach or other failure modes. A study is being conducted within the framework of a portfolio risk assessment for Huntington District dams which will develop a tool for establishing a risk and uncertainty correlation for an implemented FWS against a catastrophic failure. The risk assessment is not intended to make dam safety decisions, but merely to aid in the planning for such decisions.