The 2019 PMP Study was a peer-reviewed, regionally coordinated effort to update extreme precipitation estimates for Arkansas, Louisiana, and Mississippi. The study used modern methodologies and existing science to develop improved data, tools, and procedures for estimating Probable Maximum Precipitation (PMP)—critical information for evaluating spillway adequacy in dam design and safety.
Historically, PMP estimates were based on outdated Hydrometeorological Reports (HMRs) 51, 52, and 55A from the National Oceanic and Atmospheric Administration (NOAA). However, the reliability and relevance of these reports have diminished over time, prompting Arkansas and neighboring states to prioritize the development of new tools better suited for today’s regulatory and technical needs.
Recognizing their shared meteorological and geographic characteristics, Arkansas, Louisiana, and Mississippi partnered on a regional approach. The result: a GIS-based PMP Evaluation Tool for estimating precipitation depth, area, and duration relationships tailored to individual basins in the region.
PMP Evaluation Tool
The PMP Evaluation Tool is a Python-based script that runs within the ESRI ArcGIS environment (ArcGIS Desktop Basic, version 1.4 or later required). The tool allows users to:
- Define a drainage basin or area of interest
- Select desired precipitation durations
- Access gridded PMP values (90 arc-seconds spatial resolution)
- Generate basin-averaged PMP depths
- View temporally distributed precipitation accumulations
Users should be familiar with ArcGIS software basics to operate the tool effectively.