Probable Maximum Precipitation (PMP)
The current Probable Maximum Precipitation (PMP) dataset covering North Dakota was derived in the 1970s and 1980s as part of Hydrometeorological Reports (HMRs) completed by the National Ocean and Atmospheric Administration (NOAA). HMR-51 consisted of the continental US east of the 105th meridian, while HMR-48 was done specifically for the Red River of the North and the Souris River. HMR-48 PMP values include influences attributable to snowmelt, which has proven to influence runoff and flooding.
Since the completion of the HMRs, North Dakota has experienced a wet-cycle that was not prevalent during the climate record used in previous studies. This period consisted of a number of large spring floods and precipitation events. Many of the historic flooding events in North Dakota occurred due to melting snow or rain on snow events, most recently in 1997, 2009, 2010, and 2011.
This study’s purpose is to develop more representative PMP estimates for evaluating flood safety, assessing flood risk, and calibrating event-specific hydrological models.
Currently, the manner in which PMP values are calculated is inconsistent and cumbersome, from the use of hand calculations to coarse chart estimations. This study aims to provide the public a user-friendly tool to estimate PMP values.
This project is managed by a Review Board. The Review Board consists of both state and federal agencies with direct knowledge of the sciences and methods involved in a PMP analysis. Headed by the Water Commission, the remaining members of the Review Board are the National Weather Service (NWS) offices of Bismarck, ND and Grand Forks, ND, the Natural Resources Conservation Services (NRCS) office in Bismarck, ND, the North Dakota State Climatologist at the North Dakota State University (NDSU), and the United States Army Corps of Engineers (USACE) Omaha District. This board was developed with the intent to guide the NDSWC program, maintain the analysis integrity through participation in meetings and discussions, and review the deliverables and final products.