Evaluation of Probable Maximum Precipitation (PMP) for West Virginia to Predict Current and Future PMP

Abstract

Probable maximum precipitation (PMP) is essential for dam design criteria. West Virginia Department of Environmental Protection Dam Safety utilizes the 6-hr, 10-mi² (26-km²) PMP established by Hydrometeorological Report 51 based on the analysis of extreme rainfall. These PMP are outdated because there have been unaccounted for extreme rainfall events that have occurred since 1978. In addition, a zone of uncertainty around the Appalachian Mountains exists, including West Virginia (WV). The objective of this research was to determine the PMP throughout WV by studying the area of uncertainty and consider rising dew points to predict future PMP. This study created an updated PMP map of WV, focusing on the maximization of the 1942 Smethport, PA storm. A watershed-specific analysis was conducted at all dams in the state with an approximate watershed area of 10-mi² (26-km²). Current PMP estimations and projections for 2100 were determined. Iso-lines were determined to develop the new updated PMP map for WV that displays current and future PMP estimations. Results suggest that the greatest values of PMP occur in the western region of the state; lowest values of PMP occur in the south-eastern part of the state. The Smethport, PA storm (1942) was considered the governing storm for the entire state; however, it may not apply to  the eastern panhandle and Potomac highlands. These regions should be considered for additional analysis. The updated PMP map will be a resource for those involved in dam inspection, repair, design, and modification.