An Interdisciplinary Examination of the Johnson County, Texas May 2024 Flash Flood Event

A multi-hazard severe weather event unfolded during the overnight hours of 4 May into 5 May 2024 across North Texas. Heavy rainfall associated with the event resulted in devastating flash flooding across the region, most notably in Johnson County, Texas located south of the DFW Metroplex. Numerous roads were covered with fast-moving water and some roads were washed out or damaged. Nearly 20 swift water rescues were conducted, and water entered nearly a dozen structures across the county.

A multi-faceted approach to surveying the flash flood impacts was conducted by the National Weather Service (NWS) Weather Forecast Office in Fort Worth, Texas and the National Severe Storms Laboratory (NSSL) as part of a collaborative flash flood research project. This study included the use of ground surveys, high-resolution satellite tasking, data collection from broadcast and social media, information from local officials, results from online societal surveys, and traffic mobility data. Each identified impact was assigned a value using the Flash Flood Severity Index (FFSI) to spatially quantify the severity of the event, and the data points and corresponding FFSI values were then gridded for comparison with products from the Flooded Locations and Simulated Hydrographs (FLASH) system to help improve the operational use of FFSI and FLASH. Additionally, this study examines some of the lessons learned from a warning operations perspective, the application of FFSI, and how findings from the survey can help drive new efforts to improve warning operations and messaging.