From Floods to FIM: How NWS Flood Inundation Mapping (FIM) Performed During the April 2024 Ohio Valley Floods

The public release of the National Weather Service (NWS) forecast-based Flood Inundation Mapping (FIM) offers exciting new possibilities for enhancing communication about river flood hazards and forecasts. By visually representing flood threats on maps, forecasters and users gain real-time and projected flood insights to support life- and property-saving decisions.

NWS FIM Services were officially launched in the WFO Pittsburgh area in October 2023 as one of the offices in the first 10% (of the population). Leading up to and just after the release, there was little opportunity to test out these services in real-time. However, that changed in April 2024 when the upper Ohio valley experienced its first significant flood event with the FIM services publicly available. Late-winter dryness quickly gave way to early-April rain, resulting in impactful stream and river rises across the upper Ohio Valley, with crests exceeding levels not experienced in nearly 20 years. Numerous requests for hydrologic support were made to NWS Weather Forecast Office Pittsburgh (WFO PBZ). In collaboration with the Ohio River Forecast Center (RFC), FIM reviews were completed through various methods, fulfilling the needs of NWS Core Partners.

Since this was the initial test of NWS FIM in the Ohio Valley, which contains numerous flood control reservoirs and navigational structures, several logistical and data-quality concerns needed to be addressed collaboratively by WFO PBZ, the Ohio RFC, and the National Water Center (NWC). Real-time fixes were also performed by the NWC Geo-Intelligence Division (GID) to address calculation errors that produced over-inundation in the City of Pittsburgh. This presentation highlights ways that WFO PBZ and Ohio RFC incorporated this new dynamic service into NWS flood operations and lessons learned from the event.