Reevaluating Spillway Adequacy of Existing Dams

Spillway capacity is a vital factor in the review of the safety of a dam, particularly where overtopping could jeopardize human lives or cause catastrophic economic loss. The determination of the adequacy of spillways of existing dams should be based on a thorough economic analysis of the cost of risks and the cost of modifications. Modification is appropriate from an economic standpoint only if the total of these two costs is reduced. Proposed standards enable an engineer to determine an acceptable level of safety at a cost commensurate with the risks. If there are compelling reasons for selecting other than the lowest total cost, the reasons should be explained and the additional cost revealed. The economic analysis requires consideration of values of human life.