Natural disasters Group3
Published on: Mar 3, 2016
Transcripts - Natural disasters Group3
Natural disasters connected with water
A natural disaster is a major adverse event
resulting from natural processes of the Earth;
examples include floods, volcanic eruptions,
earthquakes, tsunamis, and other geologic
processes. A natural disaster can cause loss of
life or property damage.
Natural disasters include
Meteorological phenomenon occurring over areas
of the seas and oceans in the form of strong,
gusty wind not less than 8 ° on the Beaufort
scale. Stormy weather is usually accompanied by
high water waves. Often there are also some
nasty showers of rain which limit the visibility.
Flooding may occur as an overflow of water from water bodies, such as a river or lake,
in which the water overtops or breaks levees, resulting in some of that water escaping
its usual boundaries, or it may occur due to an accumulation of rainwater on saturated
ground in an areal flood.
Types of floods:
Areal (rainfall-related) Floods can happen on flat or low-lying areas when the ground is
saturated and water either cannot run off or cannot run off quickly enough to stop
Riverine - river flows may rise to flood levels at different rates, from a few minutes to
several weeks, depending on the type of river and the source of the increased flow.
Estuarine and coastal - flooding in estuaries is commonly caused by a combination of
sea tidal surges caused by winds and low barometric pressure, and they may be
exacerbated by high upstream river flow.
a series of waves in a body of water caused by the displacement of a large volume
of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions
and other underwater explosions (including detonations of underwater
nuclear devices), landslides, glacier calvings, meteorite impacts and other
disturbances above or below water all have the potential to generate a
There are three types of tsunamis:
Local - the epicentre is close to the coast, and the time of the wave arrival is
estimated to half an hour,
Regional - waves could threaten greater coastal areas. The time of arrival of
the wave is estimated to 5 hours since the start,
trans-regional (Pacific) - can cover many areas on both sides of the Pacific.
Time that the wave needs to reach the area ranges from few to several hours
depending on the epicentre.
It is liquid water in the form of droplets that have
condensed from atmospheric water vapor and then
precipitated—that is, become heavy enough to fall
under gravity. Raindrops impact at their terminal
velocity, which is greater for larger drops due to their
larger mass to drag ratio. At sea level and without wind,
0.5 mm drizzle impacts at 2 m/s or 7.2 km/h, while
large 5 mm drops impact at around 9 m/s or 32 km/h.
In certain conditions precipitation may fall from a cloud
but then evaporates or sublimes before reaching the
ground. This is termed virga and is more often seen in
hot and dry climates.
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