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Driving through a flash flooded road
Driving through a flash flooded road

A flash flood is a rapid flooding of geomorphic lowlying areas - washes, rivers and streams - caused by the intense rainfall associated with a thunderstorm, or multiple thunderstorms. Flash floods can also occur after the collapse of an ice dam, or a human structure, such as a dam, for example, the Johnstown Flood of 1889. An ice dam (or ice jam) occurs when water builds up behind a blockage of ice The Johnstown Flood disaster (or Great Flood of 1889 as it became known locally occurred on May 31, 1889. Flash floods are distinguished from a regular flood by a timescale less than six hours.

Contents

Causes

Flash flooding occurs when the ground becomes saturated with water that has fallen too quickly to be absorbed. The runoff collects in low-lying areas and rapidly flows downhill. Flash floods most often occur in normally dry areas that have recently received precipitation, but may be seen anywhere downstream from the source of the precipitation - even dozens of miles from the source.

Flash floods may occur after a volcanic eruption as a result of the change in weather such as thunderstorms and the soil getting over soaked.

Hazards

The United States National Weather Service gives the advice "Turn Around, Don't Drown" in reference to flash floods; that is, it recommends that people get out of the area of a flash flood, rather than trying to cross it. Most people tend to underestimate the dangers of flash floods.

Flash floods are extremely dangerous because of their sudden nature. Being in a vehicle provides little to no protection against being swept away; it may make people overconfident and less likely to avoid the flash flood. More than half of the fatalities attributed to flash floods are people swept away in vehicles when trying to cross flooded intersections. [1] As little as two feet of water can be enough to carry away most SUV-sized vehicles. A sport utility vehicle ( SUV) is a generic marketing description for a rugged automotive vehicle similar to a Station wagon but built on a light-truck chassis [2] In the United States, the National Weather Service (part of the National Oceanic and Atmospheric Administration) reported in 2005 that, using a national 30-year average, more people die yearly in floods (127 on average) than by lightning (73), tornadoes (65), or hurricanes (16). The National Oceanic and Atmospheric Administration ( NOAA) is a scientific agency within the United States Department of Commerce focused on the conditions of the Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or A tornado is a violent rotating column of air which is in contact with both the surface of the earth and a Cumulonimbus cloud or in rare cases the base of a Cumulus A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding [3]

The desert southwestern U.S. is especially dangerous for both hikers and vehicles from the sudden onslaught of water from isolated thunderstorms. The Southwestern area of the United States could be defined as the states west of the Mississippi River, with the qualification of a certain northern limit such as the 37 These rains fill poorly-absorbent and often clay-like dry riverbeds. Clay is a naturally occurring material composed primarily of fine-grained Minerals which show plasticity through a variable range of Water content, and A moving flood will usually be headed by a debris pile that may have wood branches and/or logs. Deep slot canyons can be especially dangerous to hikers as they may be flooded by a storm that occurs on a mesa miles away, sweeping through the canyon, making it difficult to climb up and out of the way to avoid the flood. A slot canyon is a narrow Canyon, formed by the wear of water rushing through rock A mesa ( Spanish, Portuguese and Arabic for "table" is an elevated area of land with a flat top and sides that are usually steep cliffs Valley roads frequently cross dry river and creek beds without bridges. From the driver's perspective, there may be clear weather, when unexpectedly a river forms ahead of or around the vehicle in a matter of seconds. [4]

Historical examples

See also

Further reading

References

  1. ^ Watches, Warnings & Advisories—Flash Flood Warning. [[National Weather Service (United States)|]]. Retrieved on 2007-06-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 524 - Battle of Vézeronce, the Franks defeat the Burgundians
  2. ^ A Preparedness Guide to flash floods #1 weather-related killer in the United States. U.S. Department of Commerce, National Oceanic and Atmospheric Administration National Weather Service, FEMA, American Red Cross (July 1992). The United States Department of Commerce is the Cabinet department of the United States government concerned with promoting Economic growth The National Oceanic and Atmospheric Administration ( NOAA) is a scientific agency within the United States Department of Commerce focused on the conditions of the The National Weather Service ( NWS) once known as the Weather Bureau is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration The purpose of FEMA is to coordinate the response to a Disaster which has occurred in the United States and which overwhelms the resources of local and state authorities The American Red Cross (also known as the American National Red Cross) is a humanitarian organization that provides emergency assistance disaster relief and education inside Retrieved on 2007-06-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 524 - Battle of Vézeronce, the Franks defeat the Burgundians
  3. ^ Turn Around Don't Drown. Retrieved on 2007-06-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 524 - Battle of Vézeronce, the Franks defeat the Burgundians
  4. ^ Thomas McGuire. Earth Science: The Physical Setting (PDF) 571. AMSCO School Publications. Retrieved on 2007-06-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 524 - Battle of Vézeronce, the Franks defeat the Burgundians
  5. ^ November 2006 Flooding. NPS. Retrieved on 2008-01-08. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 871 - Battle of Ashdown - Ethelred of Wessex defeats a Danish invasion army
  6. ^ Flash floods kill 125 in Ethiopia. BBC. Retrieved on 2007-07-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 324 - Battle of Adrianople Constantine I defeats Licinius, who flees to Byzantium.

External links

Dictionary

flash flood

-noun

  1. A sudden, rapid flood, usually of short duration and local impact
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