How much do flash flooding events outside an Excessive Rainfall Outlook (ERO) matter?

Authors: Meirah Williamson*, University of Florida, Kevin Ash, University of Florida, Michael J Erickson, Weather Prediction Center, Esther Mullens, University of Florida
Topics: Hazards, Risks, and Disasters, Water Resources and Hydrology, United States
Keywords: flash flooding, floods, hazards
Session Type: Virtual Paper
Day: 4/8/2021
Start / End Time: 3:05 PM / 4:20 PM
Room: Virtual 41
Presentation File: No File Uploaded


Flash flooding is the most damaging and deadly type of flooding in the continental United States (CONUS), and one of the deadliest natural hazards worldwide. The Excessive Rainfall Outlook (ERO) is used by the National Weather Service’s (NWS) Weather Prediction Center (WPC) to highlight regions at risk of flash flooding. This research investigates the geographic distribution and seasonality of flash flooding events missed by EROs across CONUS and their associated monetary damages from 2016-2020. We find that Summer (June-August, JJA) experiences more missed flash flooding events than any season, particularly in the Rocky Mountain region and lower Mississippi River Valley. Winter (December-February, DJF) experiences missed flash flooding events frequently in the Cascade Mountain region and Sierra Nevada Mountain region. Summer experiences higher damages and more counties with damages than any season. The Southwest US experiences more damages from missed flash flooding events compared to other regions across all seasons. Overall, damages from missed flash flooding events are proportionally small (3.1%) relative to all flash flooding damages recorded for this period. Understanding the geographic distributions of damaging flash flooding events outside of EROs could aid the WPC in improving EROs, giving the public, local weather stations, and emergency managers more confidence in understanding their localized flash flooding risk.

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