Today’s topic during this Flood Safety and Wildfire Awareness Week is flash floods.
Flash floods are no strangers to
Colorado. Since the year 1900 nearly 300 people have been killed in flash
floods across the Centennial State.
Flash Flood History
In terms of lives lost the worst
flash flood occurred on July 31, 1976 in the Big Thompson Canyon between Estes Park
and Loveland. A nearly stationary storm
produced around 12 inches of rain in four hours claiming 144 lives.
Three other notable flash floods
in Colorado were:
- In 1904 just north of Pueblo a bridge failed and around 100 people drowned when a passenger train plunged into Fountain Creek.
- Last year nine people drowned during the historic September rain episode, which was a combination of flash floods and river floods. These floods were much more extensive than the Big Thompson Canyon flood of 1976, but because of timely and accurate warnings many lives were saved.
- The 1997 Fort Collins episode killed five people and caused $200 million of property damage.
Flash Flood
A flash flood is defined as a
rapid rise in water levels generally occurring in less than six hours along large
creeks, normally dry washes, arroyos or over normally dry land area and can
occur with little advanced notice.
Flash floods frequently result
from high rainfall rates and infrequently result from dam failures, levee
failures or sudden breaks in river ice jams.
Flash floods are very destructive due to the force of the moving water and
the accompanying debris. This tremendous force can easily damage or destroy
roadways, bridges and buildings.
In recent years Colorado has seen
major flooding and damage when heavy rains have occurred on wildfire burn scar
areas. If you are in or near a burn scar
area you need to plan ahead. Be aware of
general flash flood plans and procedures that have been developed and
implemented by your local emergency management officials. You should know your
flash flood risks and make your plans to save your life and those around you.
The National Weather Service
forecast offices will discuss flash flood potential in Daily Hazardous Weather
Outlooks and in Graphical Weather Stories on National Weather Service forecast
office web sites.
During days when flash flooding
is possible a flash flood watch will be issued.
During days when flash flooding
is likely or occurring a flash flood warning will be issued.
When a flash flood warning is
issued for your area you need to act quickly if you are in a drainage area or
in other low spots. Know your escape
routes to higher ground and act as quickly as possible. It may be just a short
walk or climb to that higher ground.
Many flash flood deaths occur in
vehicles. Do not drive through a flooded
roadway. The water may be much deeper
than you think because the roadway may be damaged or washed away. One to two
feet of water will carry away most vehicles. Instead turn around, don’t
drown.
For more information on flood
safety go to Http://www.floodsafety.noaa.gov.
Flood Safety and Wildfire Awareness Week continues through this Saturday.
This blog written by Tom Magnuson,
Warning Coordination Meteorologist, National Weather Service Pueblo
