Forces of Nature: Floods
Some more
A flood may also occur when volcanic eruptions melt a large amount of
ice and snow quickly.
 Undersea earthquakes, eruptions of island volcanoes that form a large
crater called Caldera (such as Thera or Krakatau), and marine landslips
on continental shelves may all engender tsunamis.
Under some rare conditions associated with heat waves, flash floods from
quickly melting mountain snow have caused loss of property and life.
Above all
There is one major cause apart from geology or weather: Human. The
distribution of human populations near water is a major cause for
concern. We have built cities and communities by the sea and rivers for
easy access to cheap transportation and for food sources and trade. The
fertile soil has attracted agriculture and other developments throughout
the ages.
But, this fertile soil in a river delta is subject to regular flooding
due to variation in precipitation or rainfall. Floods happen when soil
and vegetation cannot absorb all the water.
Even the extensive and elaborate protection systems fail to prevent
floods. They may result in much greater flooding downstream and in
locations where they break, as they increase the difference between the
water level during flood and the surface of the inland.
 Dikes and Levees: Earthen dams,
such as dikes, dunes or buffs, are embankments of earth and rock built
across rivers to dam them up. Levees are made alongside rivers to keep
them from overflowing. However, both can fail because of heavy rainfall,
earthquake, internal erosion, engineering and construction faults, or
avalanches.
Concrete dams:
Concrete dams holdback water in man-made lakes called
reservoirs. The water is released through floodgates at a regular pace
so it doesn’t overflow the rivers below the dams. But, engineering and
construction faults, and the location of the dam may result in failures.
Say, building a dam in an area that experiences frequent earth movements
may cause disasters.
Destruction
Rushing water is extremely powerful. Imagine gallons of water crashing
through the streets at 80 miles per hour! The water also carries along
mud, earth, boulders, and other debris… actually, anything not firmly
attached to the ground. In 1955, a flood in the US carried away a
wooden, four-story hotel!!!
The water sometimes mixes with oil and sewage, destroying buildings and
objects. Roads, railroads and bridges
are often broken or washed away. Communication is difficult. Even after
the water drains away, a lot of destruction is left behind. In 1887 in
China, more than a million residents starved to death because a flood
ruined crops, leaving no other source of food!
Floodwater is also polluted, spreading diseases such as typhoid fever,
cholera, hepatitis-A, malaria, dengue and yellow fever.
Conclusion
Floods are the most frequent type of disaster worldwide. Floods are
already wreaking havoc in many states of India. Nowadays, strategies to
deal with floods also include evacuation strategies.
Although nature is generally blamed, most often it is the direct or
indirect effect of human action that triggers a flood. Can we then
prevent this catastrophe? Think about it and tell us ‘how’? |
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