'Flood Inundation Mapping: A New Paradigm of Hydrologic Impact-Based Decision Support Services'

In late April and early May 2024, multiple heavy rainfall events occurred across southeast Texas, especially over portions of the Brazos Valley and Piney Woods regions. Rainfall totals exceeded 20” for portions of Walker, Trinity, Polk, San Jacinto, and Montgomery counties over five days. These rounds of excessive rainfall led to widespread moderate to major, and isolated record river flooding especially along the Trinity, San Jacinto, and portions of the Brazos Rivers. While many tried to compare this event to Hurricane Harvey back in 2017, there were stark differences in the atmospheric conditions, location of the maximum rainfall, and tools used for issuing advisories, watches, and warnings. The new Flood Inundation Mapping (FIM) services, provided by the Office of Water Prediction, also provided an enhanced level of Impact-based Decision Support Services (IDSS) by showing detailed maps of current and forecast flooding during this recent event. Over the course of the multi-day flood event, over 150 targeted inundation maps were used to pinpoint areas of ongoing and potential riverine flooding that aided partner decisions in planning, response, and recovery. This set the stage for a new paradigm of hydro IDSS in southeast Texas. An After Action Review (AAR) was conducted with core partners to review the new service and gather necessary feedback in FIM accuracy and service delivery. The lessons learned and best practices have been captured and are being evaluated for use in local operational plans to improve services in future events. This talk will review the findings from the AAR, as well as recommendations for enhancing the new hydro IDSS paradigm of the National Weather Service.