However, unless the runoff characteristic of the watershed were to change, increments in future estimates for a specific basin resulting from extension of the data base should, in general, be less than those noted in the past. A clam designed for the estimated probable maximum flood, based on the estimated probable maximum precipitation as determined by current practices, does not necessarily provide absolute assurance that the dam is safe for every possible flood. During the past 20 years, there have been major advances in our knowledge of earthquake ground motions, in our abilities to predict resul- tant structural response, and in the methods of analyzing the safety of dams against earthquakes. Each approach has advantages and disadvantages that must be evaluated in selecting an appropriate method for any specific project. At the present time, the deterministic-statistical and the seismotectonic approaches are the most widely used.
Risks are present in every human activity.
The federal government has become increasingly involved in risk management issues in the last two decades. A number of federal agencies have developed various risk manage- ment standards for specific types of risk, but these are not applicable to risk management for dams. Adaptation of these concepts to dam safety requires research that has not been done by this committee. Court decisions relating to dam failures in general have held the owner liable for the damages resulting from a failure. To the extent practicable, reservoir safety evaluations should strike a balance among such considerations as project benefits, construction costs, social costs, and public safety, including the possible consequences of dam failure due to major earthquakes and floods.