The NWS Louisville Flash Flood Hotspot Program

According to statistics from the National Weather Service (NWS), over a 30-year period from 1984-2013, flooding/flash flooding was the leading cause of death from weather-related hazards in the United States. However, effective warnings for flash flooding can be difficult. It depends not only on rainfall intensity and amount, but also on antecedent ground wetness, terrain, and road conditions. Small-scale terrain variations and road conditions like low-water crossings can be particularly challenging given forecaster unfamiliarity with these factors. To mitigate such challenges, a project was begun in the late 1990s at NWS Louisville, Kentucky to identify flash-flood-prone locations in each of the 59 counties served by the office.

Extensive collaboration between NWS Louisville and emergency managers and road departments in each county allowed identification of many areas prone to flash flooding. These locations were mapped and classified on a low-medium-high scale depending on the propensity for flooding. With the advancement of Geographic Information System (GIS) programs in the 2000s, the maps were converted to GIS shapefiles and incorporated into webpages and the NWS's Advanced Weather Interactive Processing System (AWIPS) for easy access by warning forecasters. Recently, past flood fatalities at hotspots were incorporated into the dataset.

The next step will be to work with emergency managers and road departments to identify changes to hotspot locations that have occurred in the years since the project's inception. This presentation will discuss the evolution of the flash flood hotspot project and how NWS Louisville forecasters incorporate critical data to more effectively communicate flash flood risks to customers.