Geoscience Reference
In-Depth Information
g
Dyked or reclaimed land
Subject to storm surge flooding
Bangladesh
Dacca
India
Kolkata
Bay of Bengal
0
100
200km
Path of 13 November 1970 cyclone in the Bay of Bengal and location of embankments protecting low-lying islands in Bangladesh.
Fig. 3.10
event. In the 1985 event, 100 000 people lost their
lives.
The response in Bangladesh to tropical cyclones
appears to be one of ignorance and acceptance of
the disaster as the 'will of God'. Cyclones cannot be
avoided and one must simply wait out the storm and
see what happens. With a bit of luck a family that has
experienced one cyclone storm surge in its lifetime will
not experience another. In 1970, only 5 per cent of the
people who survived had evacuated to specific shelters
while 38 per cent had climbed trees to survive. Many
view evacuation as unwise because homes could be
looted. Even if evacuation had been possible, religious
taboos in 1970 would have prevented Moslem women
from leaving their houses because the cyclone struck
during a month when women were forbidden by estab-
lished religious convention from going outside. Since
1970, 1841 cyclone shelters have been built by Caritas
Bangladesh and other non-government organizations.
These shelters are built of reinforced concrete and
raised on piers at least 4.6 m above historical storm
surge levels. They can double as schools, family welfare
centers, mosques, markets, and food stores during
normal times. Each shelter is designed to give a person
0.5 m
2
of floor space, which is sufficient to allow them
to sit comfortably on the floor during storms. When
filled to capacity with people standing shoulder-to-
shoulder, this personal space decreases to 0.14 m
2
.
Toilet facilities and potable water supplies pose
problems under these latter circumstances. A shelter
can hold 1000-1500 people and some livestock. Up to
50 per cent of the population can now be accommo-
dated in cyclone shelters. Their effectiveness was
proven on 28 May 1997 when tropical cyclone Helen
hit the Chittagong region. A million people took refuge
in 700 cyclone shelters for up to 20 hours. Winds of up
to 230 km hr
-1
damaged 600 000 houses in south-east
Bangladesh. Instead of a death toll in the tens of
thousands, only 106 people were killed.
EXTRA-TROPICAL CYCLONES
Extra-tropical cyclones or depressions are low-
pressure cells that develop along the polar front. They
also can develop over warm bodies of water outside the
tropics, usually off the east coast of Australia, Japan,
and the United States. This section will describe the
formation of low-pressure storms due to upward
forcing of warm air along the polar front, and the
formation of
east-coast lows
that develop or intensify
over bodies of warm water along limited sections of the
world's coastline.
