December 6. 2007
NOAA meteorologists in California are forecasting tomorrow's approaching Pacific storm will drop up to three inches of rain on burned areas that lost trees, shrubs and other vegetation during last month's wildfire. Without vegetation these burn scar areas are vulnerable to flash floods and debris flows (mud slides).
“The potential for flash flood debris flow is very high, even a moderate amount of rain in a short period of time falling on a burn scar can lead to serious problems,” said Jim Purpura, meteorologist in charge of NOAA's National Weather Service office in San Diego. “Rainfall, which is normally absorbed by vegetation, can run off almost instantly, causing creeks and drainage areas to flood much sooner and with more water than normal.”
Soils in a burn scar are highly susceptible to erosion causing floodwaters to contain significant amounts of mud, boulders and remaining vegetation. The powerful force of rushing water, soil and rock downstream can destroy culverts, roadways, structures and bridges, resulting in injury or death.
People should take precautions to protect themselves by moving to higher ground immediately if they should happen to be in a burn area and rain is falling. Nearly half of all flash flood fatalities are auto related. While driving in flood prone areas, be on the look out for flooding at highway dips, bridges and low areas. Never attempt to drive over a flooded road where you could be stranded or trapped by rushing water. If your vehicle stalls leave it immediately and seek higher ground. Rising water can engulf the vehicle and sweep it away. The best advice when you are in a vehicle is to TURN AROUND...DON’T DROWN.
Flood watch and warning information is available on National Weather Service web pages or by calling your local NWS Weather Forecast Office. You may also tune into NOAA Weather Radio. NOAA Weather Radio is a nationwide network of radio stations broadcasting continuous weather and river information direct from nearby National Weather Service offices.