Flood Hydrology

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Extreme flood do occur. Learn more here

Hydrology is essential not only in the design of a dam, but also in the feasibility study of a dam and in assessments of the dam into the future as the state-of-the-practice evolves. The three main components of flood hydrology, according to the United States Bureau of Reclamation (USBR) are “(1) hydrometeorology related to probable maximum precipitation determinations, (2) probable maximum flood hydrograph determinations, and (3) statistics and probabilities relating to the magnitude and frequency of flood flows”.

“One of the most common causes of dam failures is the inability to safely pass flood flows. Failures caused by hydrologic conditions can range from sudden failure, with complete breaching or collapse of the dam, to gradual failure, with progressive erosion and partial breaching”. Therefore, hydrologic studies are among the most important sources of information when it comes to dam safety.

Methodologies

• Regression
• Stream Gage Analysis
• Rainfall-Runoff Modeling
• Stochastic Modeling
• Paleohydrology

Examples

Learn more about the occurrence of extreme floods at DamFailures.org

Best Practices Resources

Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94) (Federal Emergency Management Agency)

Hydrologic Engineering Requirements for Reservoirs (EM 1110-2-1420) (U.S. Army Corps of Engineers)

Engineering Guidelines for the Evaluation of Hydropower Projects: Chapter 8- Determination of the Probable Maximum Flood (Federal Energy Regulatory Commission)

Technical Release 210-60: Earth Dams and Reservoirs (Natural Resources Conservation Service)

Design Standards No. 14: Appurtenant Structures for Dams (Ch. 2: Hydrologic Considerations) (Bureau of Reclamation)

Flood Hydrology Manual (Bureau of Reclamation)

Trainings

Dam Owner Academy: Extreme Rainfall Events

Citations:

Revision ID: 5214
Revision Date: 12/13/2022