7-23 Accuracy of flood inundation maps during Helene 2024

Session: Undergraduate Research, Part I (Posters)

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Abstract:

Flooding remains one of the most frequent and destructive natural hazards in the United States, with increasing risk in rapidly urbanizing regions such as Greenville, South Carolina. Accurate inundation maps informing areas of risk clearly marked are essential for effective emergency response and mitigation planning. This study evaluates the performance of a two-dimensional hydraulic model to reconstruct and simulate an extreme event and assess the accuracy of inundation mapping products produced by the Federal Emergency Management Agency (FEMA) and the City of Greenville. The HEC-RAS model was developed using data collected from field work at Unity Park, South Carolina, along with stage data from the United States Geological Survey (USGS), land use data, and topographic data to simulate hydrographs and peak discharge for Hurricane Helene. These outputs were compared against observed streamflow data and existing flood hazard boundaries from FEMA’s Flood Insurance Rate Maps and Greenville’s local inundation mapping. Preliminary results indicate that while FEMA and city maps provide valuable long-term planning options, they may underestimated flood extent in urbanized watersheds where rapid runoff occurs. This research shows how important it is for there to be a constantly updated inundation map that takes into account both climate change and population growth.

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