Hurricane Fatalities: Why Torrential Rainfall Tops the List of Deadly Threats

Hurricane Debby is currently stalling off the Georgia and Carolina coasts as a tropical storm. Experts warn that the region may experience potentially deadly rainfall totals over the next few days.

Debby struck the Big Bend region of Florida as a category 1 hurricane on August 5, 2024. Although it has since weakened into a tropical storm, projections indicate it will have severe impacts on coastal Georgia and the Carolinas. The region could see over 20 inches of rain, leading to hazardous conditions.

Despite its reduced strength, the storm’s impact should not be underestimated. Social media discussions have downplayed Debby’s significance due to its sub-hurricane wind speeds. However, questions on Google reveal public curiosity about the real threats posed by such storms.

Is flooding caused by excessive rainfall the leading cause of hurricane deaths?

Yes, freshwater flooding caused by excessive rainfall is indeed the leading cause of hurricane-related fatalities.

Research shows most direct hurricane deaths result from either freshwater flooding or coastal flooding due to storm surge. Even category 1 hurricanes and tropical storms can produce fatal flooding and storm surges.

According to the American Meteorological Society (AMS), between 2013 and 2022, 57% of all direct hurricane deaths in the U.S. Atlantic basin were attributed to freshwater flooding from rain. During the same period, deaths caused by surf and rip currents accounted for 15%, wind for 12%, and storm surge for 11%.

A study covering 1963 to 2012 found that 49% of deaths were due to storm surge, and 27% from rainfall-triggered freshwater flooding. It noted that no other single factor caused more than 10% of hurricane-related fatalities.

An important finding was that 40% of deaths from the earlier study were from Hurricane Katrina, mainly due to the storm surge that flooded New Orleans. More tropical storms have caused fatalities from rain-induced floods than any other hazard.

Notably, most of the deadliest storms from 2013 to 2022 were category 1 hurricanes or tropical storms. A study highlighted that only three of the ten deadliest storms were category 3 or higher when they made landfall, emphasizing that weaker storms can still be deadly.

Rainfall potential in tropical cyclones is influenced by six factors: storm track, time of day, storm size, topography, wind shear, and nearby storms. Large and slow-moving storms tend to bring heavier rains due to prolonged precipitation over one area.

As Tropical Storm Debby lingers near the Georgia and South Carolina coasts, the region could experience prolonged periods of heavy rain. For instance, Tropical Storm Allison stalled over Houston in 2001, dropping nearly 37 inches of rain and causing 27 flood-related deaths.

Hurricane Harvey produced over 47 inches of rain in some parts of Harris County, Texas, in 2017. The county usually receives around 50 inches annually, illustrating the severe impact a stalling storm can have.

Currently, Debby is expected to produce over 20 inches of rain in areas from Charleston, South Carolina to Wilmington, North Carolina. FEMA advises residents to prepare for flooding by checking if their properties are in flood-prone zones, knowing evacuation routes, clearing rain gutters, and assembling emergency kits.