Empirical Relationships for Regional Quantification of Probable Maximum Precipitation (PMP) and Probable Maximum Floods (PMF)

Estimating extreme flooding is a safety and design requirement for various structures where failure would result in likely loss of life; examples include dams, mine tailings storage facilities, and nuclear power plants. For most of these structures, the design estimation is based on the meteorological concept of the Probable Maximum Precipitation (PMP). Various methods have been developed since the first PMP study was published by the US Weather Bureau (now National Weather Service) in 1940. Since the 1990’s, site-specific, statewide, and regional PMPs conducted mostly by private consultants have become the standard of practice for developing updated PMP depths. PMP studies completed in the last 15 years now cover more than 50% of the continental Unites States and parts of Canada. Incorporation of those PMP results in hydrologic rainfall-runoff models is used to estimate Probable Maximum Floods (PMF). Currently, there is a wealth of high quality PMP and PMF data to compile, analyze and develop regional relationships for investigation and assessment of PMP and PMF studies. This paper would present a summary of existing site-specific PMP and PMF data and regional relationships of the results of those studies.