Dam Safety Policy for Spillway Design Floods

Abstract

Dam safety risks are abhorred by the public due to the high impact of dam failures and the subjective way that people perceive risk. Therefore dam safety policies are extremely conservative, often ignoring the cost-benefit question. Unnecessary expenditures made consequent to this are unknown, but would seem to be significant. Cost-benefit issues need a more thorough airing, from both a professional and public perspective. This paper examines different approaches to selection of the spillway design flood (SDF). Opinions concerning dam safety issues were solicited from the heads of the dam safety units in the 50 states. It was found that most states pattern their SDF requirements after the Corps of Engineers guidelines developed pursuant to the National Dam Inspection Act of 1972. Dam safety professionals generally do not believe that the probable maximum flood (PMF) is unreasonably conservative, nor do they believe that existing spillway criteria are too conservative. Further, even though ASCE and the National Research Council endorse the risk analysis concept, it is not popular and is little-used.