Repository logo

Updating PMP to provide better dam and spillway design




Kappel, W. D., author
Hulstrand, D. M., author
Muhlestein, G. A., author
Colorado State University. Department of Engineering, publisher

Journal Title

Journal ISSN

Volume Title


Probable Maximum Precipitation (PMP) is used as input to derive the Probable Maximum Flood (PMF) for high hazard dams across the United States. The PMF is used to design high hazard dams to ensure they do not overtop and fail during a PMP/PMF event. PMP values were developed for most of the United States by the National Weather Service (NWS) in a series of Hydrometeorological Reports (HMRs) starting in 1940 and continuing through 1999. However, the NWS stopped updating the HMRs and the storms used to derive the PMP values. Since that time the meteorological understanding of extreme rainfall has advanced significantly and numerous large rainfall events have occurred which affect PMP. Because the dam safety community required updated PMP values which incorporated these updated data and meteorological understanding to ensure proper design and rehab of dams, Applied Weather Associates (AWA) has been performing site-specific, statewide, and regional PMP studies to update these data and advance the science regarding PMP. Beginning in the 1990's, AWA has completed more than 100 PMP studies, which have been accepted by state and Federal dam safety regulators. Each of these provide updated PMP values which replace those from the HMRs. In this process, AWA has analyzed hundreds of the most extreme rainfall events, which are required for proper PMP development. This presentation will detail the history of PMP development in the United States, provide an understanding of current PMP development, discuss the storm analysis process, and detail future improvements that are needed for dam safety.


Presented at the Protections 2016: 2nd international seminar on dam protection against overtopping: concrete dams, embankment dams, levees, tailings dams held on 7th-9th September, 2016, at Colorado State University in Fort Collins, Colorado, USA. The increasing demand for dam and levee safety and flood protection has motivated new research and advancements and a greater need for cost-effective measures in overtopping protection as a solution for overtopping concerns at levees and dams. This seminar will bring together leading experts from practice, research, development, and implementation for two days of knowledge exchange followed by a technical tour of the Colorado State University Hydraulic Laboratory with overtopping flume and wave simulator. This seminar will focus on: Critical issues related to levees and dams; New developments and advanced tools; Overtopping protection systems; System design and performance; Applications and innovative solutions; Case histories of overtopping events; Physical modeling techniques and recent studies; and Numerical modeling methods.
Includes bibliographical references.

Rights Access


probable maximum precipitation
extreme rainfall


Associated Publications