Evaluation Procedures for Hydrologic Safety of Dams

Task Committee on Spillway Design Flood Selection of the Committee on Surface Water Hydrology of the Hydraulics Division of ASCE

American Society of Civil Engineers, New York, NY
978-0-87262-652-2 (ISBN-13) | 0-87262-652-0 (ISBN-10), 1988, Soft Cover, Pg. 107

Out of Print: Not available at ASCE Bookstore.

Document Type: Book


Procedures are proposed for selecting the safety design flood for both new and existing dams. The procedures are based on a quantitative risk assessment in which the likelihood and consequences of failure under present and anticipated future conditions are evaluated. Three categories of dams are proposed depending upon failure consequences and effort required to select a design flood. A reconnaissance-level appraisal of failure consequences is adequate to select the design flood for categories 1 and 3 where damages are either very large (category 1) or low and confined to the dam owner (category 3). Category 2 requires a detailed analysis to determine the safety design flood. Selecting a safety design flood for a category 2 dam incorporates consideration of the probability of failure, the consequences of failure (both those which can be measured in monetary terms and those which cannot), and the project cost. The economic analysis of failure consequences which can be quantified in monetary terms requires the dam owner to include the cost of indemnifying possible victims of dam failure against financial loss. The social and environmental consequences which cannot be reduced to monetary terms are displayed for specific inclusion in the safety design decision based on the cost to avoid these nonmonetary consequences. Because the relative weighing of nonmonetary consequences and their comparison to dollar savings is a matter of judgment which will vary among decision makers for each site examined, no criteria are provided for making the final safety decign decision. The report discusses a number of important related issues including legal liability for dam falure and the determination of indemnification costs.

Subject Headings: Dam failures | Failure analysis | Hydraulic design | Floods | Safety | Hydrology | Dam safety | Owners


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