Flash Flooding and Thunderstorms -- A Deadly Combination
Severe thunderstorms come with its fair share of hazards like frequent lightning, gusty winds more than 57 mph and tornadoes. However, flash flooding is an often forgotten threat with any robust storm.
The National Weather Service defines a flash flood as flooding witnessed within 6 hours of heavy rainfall. However, flash flooding normally takes place within 3 hours of a heavy downpour. Flash floods occur due to the ground becoming inundated by rain too quickly for it to absorb the excess moisture. This creates the threat known as flash flooding that can sweep away loose objects and render a vehicle immobile.
Homes and business located near streams, rivers, creeks or lakes are more susceptible to flash flooding due to banks filling up and spilling over. The heavy rain could even result in mudslides, causing additional debris to be swept away in flowing water.
Even though an overfilled body of water may increase the risk of flooding, urban areas are also at risk especially if there’s not enough drainage or too much concrete. This will decrease the flowing water’s ability to be absorbed and increase the flash flooding risk.
This version of flooding is so dangerous because of its namesake, heavy rainfall that only gives unsuspecting victims mere moments to act. An example is May 19, 1990, when a wave of thunderstorms swept through Hot Springs, Ark., dropping a massive 13 inches of rainfall in only nine hours. This led to the overflowing of Lake Hamilton and breaching of the Remmel Dam. Neighboring homes, cabins and stores were drenched as flood waters ransacked the region.
According to the Centers for Disease Control and Prevention (CDC), more than half of all flood-related deaths happen when a vehicle has attempted to cross into flood waters. If you ever cross paths with a flooded roadway, “Turn Around, Don’t Drown,” since it only takes 6 inches of flowing water to knock a person over, and 12 inches to render a car useless. Never attempt to cross flood waters.
Source(s): weather.gov, National Weather Service, CDC
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Story Image: Brownsville, TX, July 24, 2008 -- Main roads are unrecognizable and hard to find due to the fast overflow of rain. (Jacinta Quesada/FEMA/Wikimedia Commons)