Evaluation of potential seepage failure modes in embankment dams and in particular around outlet works penetrations is a very important aspect of dam safety evaluations. Assessing potential seepage failure modes typically requires designing and evaluating investigation and instrumentation programs, and a variety of engineering analyses. Experience has shown that adverse seepage and piping conditions can develop and remain difficult to detect u...

This webinar provides an introductory discussion of the processes governing earth and vegetated earth spillway design and performance. Topics include the history of vegetated earth spillway use by the USDA and the associated design criteria, the concept of stability and integrity design, the importance of maintenance, and the erosion processes quantified in the SITES program. Examples from USDA NRCS experience and USDA ARS research will be use...

Physical models have been used as part of the design process for spillways and other hydraulic structures for centuries. Their use has proven to be extremely effective for validating hydraulic design schemes for new and rehabilitated spillways, for the discovery of hydraulic design problems that previously had not been expected, and in reducing construction costs. Physical modeling is also important for public relations, for reducing risk and...

With the development in Europe in the later 1800s of a rational method for evaluating structural stability combined with practical experience, U.S. engineers gained greater confidence in increasing the structural height and loadings on masonry dams, as they were known then. This lead to record setting heights in the U.S. for several gravity dams built for water supply purposes for major U.S. cities. As records were being set, a few dramatic co...

This webinar is intended to provide an introduction to emergency action plans (EAPs) for dam safety emergency planners, dam owners, dam regulators, and consultants. The information presented will be a condensed version of subjects included in ASDSO’s two-day seminar titled Emergency Action Planning for Dam Safety. The webinar will include information that will be useful to participants in developing new EAPs and improving the effectivene...

The Webinar will have four ½ hour sessions and will begin with a brief review of the Hydraulics 101 Lectures. Uniform flow, specific energy, and gradually varied flow will be covered in the first session. Hydraulic modeling and water surface profile computations will be covered in the second session and geometric data requirements will be addressed in the third session. The final session will concentrate on the development of the Hydro...

Probable Maximum Precipitation (PMP) is used to compute the Probable Maximum Flood (PMF) that in turn is used by federal and state regulators to evaluate the safety of dams. The concept of an upper limit for precipitation was presented in the 1940’s with procedures for determining PMP values developed by the Weather Bureau (now the National Weather Service), the US Army Corps of Engineers, and the Bureau of Reclamation. The definition o...

The Hydrology 201 Webinar consists of four one-half hour segments. The first segment is a brief review of Hydrology 101 emphasizing some of the important hydrologic issues. The second segment will concentrate on the NRCS procedures to determine the loss rate function and the dimensionless unit hydrograph as it is utilized to transform excess rainfall into runoff. Different methods of determining time of concentration and lag time will be cove...

The purpose of the webinar is to provide an overview of the process required to developing field investigation programs for design of new dams or rehabilitation of existing dams. The presentation will include the four phases that are typical of field investigations for new and existing dams. The presentation will highlight the important aspects of each phase from plan ning to execution, including defining the goals of each phase. Site Reconna...

The webinar will discuss the basics of various non-destructive evaluation (NDE) methods and their applications for investigating dam, spillway and conduit conditions such as freeze-thaw cracking, void, seepage, corrosion of reinforcing, anchor bolts, strength/moduli, and stability. Guidance will be provided as to which NDE methods are useful for diagnosing various conditions of concrete, masonry, earthen and steel materials. The webinar will...