Department of Conservation and Recreation
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Department of Conservation and Recreation
This study provides gridded Probable Maximum Precipitation (PMP) values (2.5 square mile grids) for any drainage basin within Virginia, including regions adjacent to the state that drain into basins within Virginia. These values replace those provided in Hydrometeorological Reports (HMRs) including, but not limited to, 40, 51, 52 and 56 (1965, 1978, 1982 and 1986 respectively). Results of this analysis reflect the most current practices used for defining PMP, including comprehensive storm analyses procedures, extensive use of geographical information systems (GIS), explicit quantification of orographic effects, updated maximum dew point climatologies for storm maximization and transposition, and an updated understanding of the weather and climate throughout the state.
The Virginia Soil and Water Conservation Board adopted the Probable Maximum Precipitation Study for Virginia and the Associated PMP Evaluation Tool and Database on Dec. 9, 2015. Here are the Impounding Structure Regulations (4VAC50-20) that made the Probable Maximum Precipitation values effective on March 23, 2016 (Section 4VAC50-20-50 was amended). The board’s Guidance Document on New Probable Maximum Precipitation Implementation became effective on that date and was revised on March 29, 2018..
Deliverables from the PMP study are available for download below.
All deliverables for the Virginia Probable Maximum Precipitation Study are being provided herein with the expressed understanding that the Virginia Department of Conservation and Recreation (DCR) and the Commonwealth of Virginia are releasing these products at the user's own risk. This study is based on the best information, science and techniques available, however no warranty, expressed or implied, is made regarding the accuracy, adequacy, completeness or reliability of the data provided. These data are provided on an "as is" basis. Neither DCR nor the contributors of said data to the DCR shall be held liable for any use or application of the data provided whatsoever, whether or not that use is improper or incorrect, and assume no responsibility for the use or application of the data or information derived from interpretation of the data. In no event shall DCR or its collaborators be liable for any direct, indirect or incidental damages arising from the use or application of these data. This disclaimer of liability applies to any damages or injury, including but not limited to those caused by any failure of performance including failures resulting in personal injury or property damage, error, omission, defect, delay in operation or transmission, computer virus, alteration, use, application, analysis or interpretation of data. It is the owner's engineer and/or other end users who are expected to take all steps necessary to ensure proper use and understanding of these products and that all information is being properly interpreted and applied.
Users should check back routinely for updates as data will be added and changed periodically resulting in some data becoming out-of-date. It is recommended that the user not let a significant period of time elapse between obtaining and using the data.
