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Flash Flooding
What Is Flash Flooding?
Flash Flooding Dangers
Flash Flooding Safety Rules
Flash Flood Watches and Warnings
What Is Flash Flooding?
In addition to tornadoes, lightning, large hail and damaging wind,
thunderstorms also produce flash flooding. A flash flood is a flood
that develops very quickly along a river or creek, low water crossing,
or along a dry streambed due to heavy rain or water releases from dams
upstream.
Flash Flooding Dangers
Flash floods can occur any time of the year and any time of the day
or night. Flooding causes more deaths each year than any other weather
event, accounting for about 140 in the United States each year. As
new construction and concrete cover soils that would have soaked up
rainfall, adding to runoff during rain events, this threat to both
life and property will continue to grow.
Flash floods are very deceptive. They occur most often at night,
when warnings may go unnoticed, and when darkness makes it hard to
find an escape route. The water is almost always deeper than it appears
to be, and moves at a swift pace. A look at flood deaths over the years
show that most flood deaths occur in cars where motorists attempt to
cross flooded roads.
Flash Flooding Safety Rules
Motorists should avoid low water crossings during thunderstorms and
heavy rain events. Use alternate routes to avoid flood prone areas.
Plan several routes to your destination during the months usually associated
with heavy storms.
If your vehicle stalls in flood waters, leave it immediately and
move to higher ground if you can do so safely. Most cars and light
trucks will begin to float in as little as 1½ feet to 2 feet
of water. If the water reaches the doors, electric window and door
systems may short out. Even if they are not shorted, occupants must
now push against the current to open doors. This is extremely difficult,
if not impossible to accomplish.
Be alert for heavy rain reducing visibility for motorists. Be especially
cautious when approaching bridges and low-water crossings. Rapidly
rising water can sweep the vehicle and its occupants away. Do not attempt
to walk through floodwaters, especially where water is above your knees.
When camping, get familiar with the terrain around you and plan an
escape route to high ground if needed. Be aware that many campgrounds
are located in valleys near creeks and rivers. Do not camp in or near
dry creek beds or other natural drainage channels when thunderstorms
are occurring or forecast. Even if thunderstorms do not occur at your
campsite, they could be producing heavy rain upstream that could send
floodwaters downstream.
Everyone, especially children, should stay away from flooded creeks,
streams or drainage ditches. The swift current can quickly sweep away
even the strongest swimmers. Soggy banks along these swiftly moving
waters become unstable after heavy rain and can easily give way, dumping
the victim into the flood waters.
Flash Flood Watches and Warnings
The best way to know when flash flooding threatens is to stay informed
of the latest weather information and warnings. Monitor NOAA weather
radio, cable or commercial television stations, or local radio stations
when thunderstorms approach or when the weather appears to be threatening.
“Flash Flood Watch” means conditions are favorable for rapid
flooding of streams, storm drains, and other low-lying areas. A “Flash
Flood Warning” means that heavy rainfall sufficient for flooding
has occurred, or that flooding has been reported.
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