Stacking the Storms: Comparing the Probable Max Precipitation (PMP) Studies from the Mid-Atlantic to Inform Better Dam Design
According to the Virginia Department of Conservation and Recreation regulations, high-hazard dams are required to pass 90% of the Probable Maximum Flood (PMF) or “most severe flood considered possible in a specific region.” The PMF results from the most severe combination of meteorologic and hydrologic conditions possible within a given drainage basin. Since the 1980s, the meteorologic component, also known as the probable maximum precipitation (PMP), has been estimated using Hydrometeorological Report Nos. 51 and 52 (HMR 51 and 52). However, recent advancements in technology and storm tracking have allowed more precise, state- and site-specific PMP studies to be performed. In 2023, Maryland Dam Safety started preliminary testing of their site-specific tool, similar to Pennsylvania and Virginia. Using dams in Virginia and Maryland as a case study, this presentation will provide results of various approaches for determining spillway rehabilitation design capacity. While the discussion will focus on the comparison of HMR 52 and the Virginia statewide PMP study results, findings from the Maryland and Pennsylvania statewide PMP studies and their applicability to the site will be presented. Impacts to the proposed rehabilitation design as a result of the newer approach to site-specific modeling and future climate change will be discussed, as well as implications of the statewide methodology on dam regulation.Author Bio
Daniel Papa: Mr. Papa has experience on a variety of water resource projects including dam safety engineering, H&H modeling, BMP design, and master planning. He has a strong understanding of HEC-RAS, utilizing both 1D and 2D models, HEC-HMS, GIS, and Civil3D. More recently, Mr. Papa has started to get more involved in active dam design and rehabilitation projects. In his free time, Daniel enjoys cheering for Boston sports teams and golfing. Jeff Powers: Mr. Powers is a technical project lead with over 300 dam design/rehabilitation projects to his credit along with over 80 dam breach analyses. Mr. Powers specializes in high-hazard dam design and renovation, river and floodplain hydraulic analysis, storm drainage system design, culvert and bridge analysis, and levee rehabilitation.
