Hazards & Disasters

Floods: The power of water

September 19, 2011, 6:36 pm
Source: National Oceanic and Atmospheric Administration
Content Cover Image

Source: National Oceanic and Atmospheric Administration.

The deadly and destructive
power of water

Be smart about floods

caption Flooded parking lot. High resolution (Credit: NOAA)

Did you know fast moving water just above your ankles can knock you off your feet? Most people do not! 

That’s why each year, more deaths occur due to flooding than from any other thunderstorm related hazard. Many of the deaths occur in automobiles as they are swept downstream. Of these drownings, many are preventable, but too many people continue to drive around the barriers that warn you the road is flooded. You will not know the depth of the water nor will you know the condition of the road under the water. 

Whether you are driving or walking, if you come to a flooded road, Turn Around Don't Drown!

Most flash floods are caused by slow moving thunderstorms, thunderstorms that move repeatedly over the same area, or heavy rains from tropical storms and hurricanes. These floods can develop within minutes or hours depending on the intensity and duration of the rain, the topography, soil conditions, and ground cover.

caption Flash flood around houses. High resolution (Credit: USGS)

Flash floods can roll boulders, tear out trees, destroy buildings and bridges, and scour out new channels. Rapidly rising water can reach heights of 30 feet or more. Flash flood-producing rains also can trigger catastrophic mud slides.

Occasionally, floating debris or ice can accumulate at a natural or man-made obstruction and restrict the flow of water. Water held back by the ice jam or debris dam can cause flooding upstream. Subsequent flash flooding can occur downstream if the obstruction should suddenly release.

Be flood safe

  • Monitor the NOAA Weather Radio All Hazards, or your favorite news source for vital weather related information.
  • If flooding occurs, get to higher ground. Get out of areas subject to flooding. This includes dips, low spots, canyons, washes etc.
  • Avoid areas already flooded, especially if the water is flowing fast. Do not attempt to cross flowing streams. Turn Around Don't Drown!
  • Road beds may be washed out under flood waters. NEVER drive through flooded roadways. Turn Around Don't Drown! If your vehicle is suddenly caught in rising water, leave it immediately and seek higher ground.
  • Do not camp or park your vehicle along streams and washes, particularly during threatening conditions.
  • Be especially cautious at night when it is harder to recognize flood dangers.

What kinds of flooding alerts does NOAA issue?

caption Flooded road. High resolution (Credit: NOAA)

FLASH FLOOD or FLOOD WATCH: Flash flooding or flooding is possible within the designated watch area — be alert.

FLASH FLOOD or FLOOD WARNING: Flash flooding or flooding has been reported or is imminent — take necessary precautions at once!

URBAN and SMALL STREAM ADVISORY: Flooding of small streams, streets and low-lying areas, such as railroad underpasses and urban storm drains is occurring.

FLASH FLOOD or FLOOD STATEMENT: Follow-up information regarding a flash flood/flood event.

caption NOAA flood safety poster. High resolution (Credit: NOAA)

What is NOAA doing about the flood and flash flood problem?

NOAA scientists are figuring out ways to blend data from radar, satellite, lightning, and rain gauges to improve flash flood monitoring and prediction. This will help overcome significant challenges in estimating precipitation type and amount. These ideas are being tested in projects around the U.S. including California and North Carolina.

Forecasters and researchers are creating a debris flow or mudslide warning system for southern California where homes are frequently destroyed and major highways have been washed out. They are focusing on burn areas that are especially susceptible to flash floods and debris flows during rainstorms because rainfall that is normally absorbed by vegetation can run off almost instantly. 

NOAA's Office of Oceanic and Atmospheric Research is working hard to improve warnings and forecasts of floods and flash floods. By investigating the meteorological causes of flash flooding and working on flash flood and river flood warning decision making tools, we hope to see more lives saved and less property destroyed.

March 14-18 is Flood Safety Awareness Week

For more information about flood watches and warnings in your area, visit the NOAAWatch Flood Warning Web site.

Posted March 17, 2011

Glossary

Citation

(2011). Floods: The power of water. Retrieved from http://www.eoearth.org/view/news/51cbf1f97896bb431f6a7650

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