Hydraulic Model Testing for Dam Safety

One of the important aspects of improving the safety of dams is selecting designs that are hydraulically efficient and cost effective. A powerful tool that can be used in parallel with the design is building and testing hydraulic models. To obtain maximum benefit from the model, it should be considered as a part of the design process. Model studies should be included early in the conceptual design phase, so that both minor and major modifications can be considered. This gives maximum flexibility to both the modeler and the designer.

Hydraulic model studies provide cost effective tangible answers to difficult problems. Some of the issues that can be efficiently resolved using model studies include; upgrading spillway capacity, controlling downstream scour, protecting earth dams against overtopping flood events, selecting a proper course of action to repair a structure when it has been damaged during a flood event, and optimizing control gate operations during floods. Model studies also allow the engineer to simulate prototype performance over the full range of expected flow rates, enabling him to observe flow conditions and patterns, and measure actual flows, velocities, pressures, scour, etc. Quick and easy changes to the model can be made at minimal cost to optimize flow conditions and to provide a safe and economical structure. This hands-on approach to dam safety provides an additional tool to the engineering process that should not be ignored.

Past model studies referred to in this paper are the Wirtz, Buchanan, Morris Sheppard, Hubbard Creek, Bay City, Lake Alan Henry, Applewhite, Stacy, and Richland Dams. All of these dams are located in south central Texas, and in each case the engineering was performed by Freese & Nichols of Austin, Texas and the hydraulic modeling was performed at the Utah Water Research Laboratory in Logan, Utah. The primary objective of each of these model studies was to provide and/or improve the safety of the dam and the spillway, while minimizing the cost. This paper discusses the cost effectiveness of performing model studies, illustrating that construction cost savings often are on the order of ten times the investment of the model study. 10 pp.