1. Flash flood
From Wikipedia, the free encyclopedia
Jump to:navigation, search
Driving through a flash flooded road
A flash flood after a thunderstorm in the Gobi, Mongolia
A flash flood is a rapid flooding of geomorphic low-lying areas - washes, rivers, dry
lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or
tropical storm or meltwater from ice or snow flowing over icesheets or snowfields. Flash
floods can also occur after the collapse of an ice dam, debris dam or a human structure,
such as a dam, for example, the Johnstown Flood of 1889. Flash floods are distinguished
from a regular flood by a timescale less than six hours. The temporary availability of
water is often utilised by plants with rapid germination and short growth cycle, and by
specially adapted animal life.It is so that flash floods are dangerous because the flood can
carry any thing in its way such as sharp items that can cause injuries. [1]
Contents
[hide]
• 1 Causes
• 2 Hazards
• 3 Historical examples
• 4 See also

2. • 5 Further reading
• 6 References
• 7 External links
[edit] Causes
Flash flooding occurs when a barrier holding back water fails or when water falls too
quickly on saturated soil or dry soil that has poor absorption ability. 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.
In areas on or near volcanoes, flash floods have also occurred after eruptions, when
glaciers have been melted by the intense heat. Flash floods mainly occur in the highest
mountain ranges of the United States.
[edit] 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. Many people tend to underestimate the
dangers of flash floods. What makes flash floods most dangerous is 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.[2]
As little as two feet of water (60 cm) can be enough to carry away
most SUV-sized vehicles.[3]
The U.S. National Weather Service 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).[4]
In deserts, flash floods can be particularly deadly for several reasons. First, storms in arid
regions are infrequent, but they can deliver an enormous amount of rain in a very short
time. Second, these rains often fall on poorly-absorbent and often clay-like soil, which
greatly increase the amount of runoff that rivers and other water channels have to handle.
In addition, these regions may not have the infrastructure that wetter regions have to
divert water from structures and roads, such as storm drains and retention basins, either
because of sparse population, poverty or because residents believe the risk flash floods
pose is not high enough to justify the expense. In fact, in some areas, desert 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.[5]
Finally, the lack of regular rain to clear water channels
may cause flash floods in deserts to be headed by large amounts of debris, such as rocks,
branches and logs.

3. 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.
[edit] Historical examples
• 1952 The Lynmouth disaster.
• 1967 Flash flood in Lisbon, Portugal. 464 dead.
• 1971 Kuala Lumpur floods, Malaysia.
• 1976 The Big Thompson River flood, which killed 143 people in Colorado.
• 1990 June 14, Shadyside, Ohio flooding.[6]
• 1990 The Quad Cities Duck Creek Floods of 1990.[7]
• 1997 Flash flood kills eleven in Antelope Canyon.
• 1998 Flash flooding in San Marcos, Texas resulted from rains totaling from 15 to
30 inches (760 mm).
• 2004 Boscastle flood.
• 2006 Mount Rainier National Park Flooding.[8]
• 2006 Flash flooding kills 125 in Ethiopia.[9]
• 2007 Sudan floods.
• 2008 The June 12–13, 2008 Floods around Duck Creek in Davenport, Iowa.[10]
• 2009 The 2009 Kentuckiana Flood resulted from 20-30 inches of rain falling in 75
minutes.
• 2009 Turkish flash floods.
• 2009 September 21–22 in 9 Georgia Counties, Killing 10 people
• 2009 September 26 in Metro Manila primarily Marikina city, Taguig City, and
Pasig City; and many municipalities of the provinces of Rizal, Bulacan and
Laguna taking more than a hundred lives and leaving thousands of affected
residents homeless. It also submerged several municipalities under feet deep of
water for several weeks.
• 2009 October 10–13 in Northern Luzon causing major landslides in Cordillera
Mountains, and submerging 80% of the Province of Pangasinan.
• 2009 In late October, a rainy nor'easter caused several flash floods in Southeast
Virginia and injured over 100 people.
• 2009 On the 25th of November, more than 100 people died in flash floods that
swept away highways and neighborhoods in the city of Jeddah, Saudi Arabia,
which was caused by heavy rains.[11]