This page last updated on 07-Nov-2011
Flooding Hazards, Prediction & Human Intervention
Hazards Associated with Flooding
Hazards associated with flooding can be divided into primary hazards that occur due to contact
water, secondary effects that occur because of the flooding, such as disruption of services,
health impacts such as famine and disease, and tertiary effects such as changes in the position of
Throughout the last century flooding has been one of the most costly disasters in
terms of both property damage and human casualties.
Major floods in China, for example, killed
about 2 million people in 1887,
nearly 4 million in 1931, and about 1 million in 1938
flood on the upper Mississippi River and Midwest killed only 47 people, but the U.S. Army Corps
of Engineers estimates the total economic loss at between 15 and 20 billion dollars (Click
for U.S. Army Corps' web site).
Again, the primary effects of floods are those due to direct contact with the flood waters.
in the video last lecture, water velocities tend to be high in floods.
As discharge increases
With higher velocities, streams are able to transport larger particles as suspended load.
Such large particles include not only rocks and sediment, but, during a flood, could include
such large objects as automobiles, houses and bridges.
Massive amounts of erosion can be accomplished by flood waters. Such erosion can
undermine bridge structures, levees, and buildings causing their collapse.
Water entering human built structures cause water damage. Even with minor flooding of
homes, furniture is ruined, floors and walls are damaged, and anything that comes in
contact with the water is likely to be damaged or lost.
Flooding of automobiles usually
results in damage that cannot easily be repaired.
The high velocity of flood waters allows the water to carry more sediment as suspended
When the flood waters retreat, velocity is generally much lower and sediment is
After retreat of the floodwaters everything is usually covered with a thick layer
of stream deposited mud, including the interior of buildings.
Flooding of farmland usually results in crop loss.
Livestock, pets, and other animals are
often carried away and drown.
Humans that get caught in the high velocity flood waters are often drowned by the water.
Floodwaters can concentrate garbage, debris, and toxic pollutants that can cause the
secondary effects of health hazards.
Flood Hazards, Prediction, & Mitigation
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