Design‐Basis Flood for Rehabilitation of Existing Dams

Abstract

Rehabilitation of existing dams in a cost‐effective manner with due regard to hydrologic safety requires a rational method to determine the design‐basis flood (DBF). Four methods are presented to determine the DBF based on economic considerations alone. These include the expected damage, indemnification cost with and without price escalation, and modified expected damage approaches. The expected damage approach is presented to provide a basis for comparison with other approaches. One of the indemnification‐cost approaches includes no price escalation and the other provides for escalation of dollar‐denominated damages attributable to dam failure that is likely to occur in the future. The modified expected damage approach considers probabilities of flood damages during the life of the rehabilitated dam, rather than the absolute probabilities. In most cases, however, consideration of nondollar‐denominated consequences of rehabilitation are equally or more important. An approach based on a combination of the delphi and fuzzy‐set methods is presented to evaluate rehabilitation alternatives with different DBFs and select the most cost‐effective and acceptable DBF, based on both economic and nondollar‐denominated factors.