1. And their effect on the built environment
They are known as Hurricanes in the Caribbean, Typhoons in the China Sea, Cyclones in the
Indian Ocean and most commonly called Tropical Cyclones. You can call them what you want but
they all have one thing in common: they are extremely destructive when they hit cities and towns.
A cyclone is a huge mass of air moving in a spiral with winds that can reach up to 250 km/h. A
cyclone starts off in the sea where the winds are calm and the water temperature is at least 240.
Warm air pushes upwards at a fast rate while cold air is sucked in below. The warm air gains
moisture and starts producing thunderclouds. Spinning in a clockwise direction (anticlockwise in
the Northern Hemisphere), the cyclone gradually picks up speed. Driven by the fast winds, the
Cyclone can move at up to 50km/h. While all this is happening a distinct "eye" is forming in the
centre of the Cyclone. This "eye" unlike the rest of the Cyclone is completely calm and is not
windy at all.
Cyclone Tracy was the most destructive cyclone recorded to hit Australia since white settlement
in 1788 (the Bathurst Bay cyclones killed 300 people but didn't reach land). Cyclone Tracy hit the
coastal city of Darwin on Christmas Day 1974. Although people had warning on New Year's Day
about Cyclone Tracy, they were busy preparing for Christmas and thought that the cyclone would
pass away just like Cyclone Selma had done three weeks before. Cyclone Tracy came roaring
down the Arafura Sea (where most the cyclones develop in that area) and was on track to bypass
Darwin but changed direction 900 past Melville Island and straight towards the city. At this time
most people were asleep or partying. By 1:00 AM, the city of Darwin felt the full effect of the
cyclone. Some people were outside when it hit but most people got to a safe place for shelter.
The cyclone had passed by 4:00 AM. Nearly 90% of the houses in the city had been damage...
Cyclone is a natural calamity. Wind blows in violent speed with ferocious sound. Heavy rain, thunder and
lightning are some other features of cyclone.
Abrupt change in atmospheric pressure is the reason of cyclone. If the pressure of atmosphere in a big area
comes down suddenly, Wind begins to blow from all around violently. We call it cyclone. Cyclone occurs very
often in the coastal regions of Orissa, Andhra Pradesh, Tamil Nadu and West Bengal. It also occurs in the
coastal regions of Bangladesh.
When cyclone occurs, wind blows at great speed, often beyond 150 kilometers per hour. Tall trees, electric
poles and towers are uprooted. Roofs are also blown away. It often causes high sea waves which rush at the
sea shore. These sea waves often pass over many villages about 20 kms. Away from the sea. Houses are

2. drowned. People are washed away and killed. Domestic animals and property are also washed away. Crops
are completely damaged. In 1996 and 1997, a terrible cyclone occurred in Andhra Pradesh. Some villages
were completely smashed in it.
In Orissa, cyclone very often affects Balasore, Kendrapara, Jajpur, Jagatsingpur, Konark, Puri, Gopalpur and
other few areas of Ganjam. Sea waves come over villages and agricultural land. Terrible wind creates large
scale damage. Massive deforestation near the sea shores the chief reason of this calamity. However, we can
to so extent control the cyclone by creating forests on sea shore.
1. Introduction: India is highly vulnerable to natural hazards especially earthquakes, floods, drought, cyclones and
landslides. Studies indicate that natural disaster losses equate to up to 2% of India’s Gross Domestic Product (GDP) and
up to 12% of Central government revenue. The cyclones that occur between Tropics of Cancer and Capricorn are known
as Tropical Cyclones. Tropical cyclones are weather systems in which winds equal or exceed gale force (minimum of 34
knot, i.e., 62 kmph).
Indian sub-continent is the worst affected region of the world, having a coast line of 7516 kms. (5400 kms along the
mainland, 132 kms in Lakshadweep and 1900 kms in Andaman and Nicobar Islands) is exposed to nearly 10% of the
world’s Tropical Cyclones. There are 13 coastal states/UTs encompassing 84 coastal districts which are affected by
cyclones (Fig. 1). Four States (Andhra Pradesh, Odisha, Tamil Nadu and West Bengal) and one UT (Pondicherry) on the
East Coast and One State (Gujarat) on the West Coast are more vulnerable to cyclone disasters. 40% of the total
population lives within 100 km of coastline. Analysed data for the period 1980-2000 shows that on an average, annually
370 million people are exposed to cyclones in India. Cyclones occur in the month of May-June and October-November,
with primary peak in November and secondary peak in May.
Although cyclones affect the entire coast of India the East Coast is more prone compared to the West Coast. An analysis
of the frequencies of cyclones on the East and West coasts of India during 1891-2000 show that nearly 308 cyclones (out
of which 103 were severe) affected the East Coast. During the same period 48 tropical cyclones crossed the West Coast,
of which 24 were severe cyclonic storms. Out of the cyclones that develop in the Bay of Bengal, over 58 percent approach
and cross the East Coast in October and November. Only 25 % of the cyclones that develop over the Arabian Sea
approach the West Coast. In the pre-monsoon season, corresponding figures are 25 percent over Arabian sea and 30
percent over Bay of Bengal.
Recurring cyclones account for large number of deaths, loss of livelihood opportunities, loss of public and private property
and severe damage to infrastructure, thus seriously reversing the developmental gains at regular intervals. Broad scale
assessment of population at risk suggests that an estimated 32 crore people, which accounts for almost third of the
country’s total population, are vulnerable to cyclone related hazards. Climate change and its resultant sea-level rises can
significantly increase the vulnerability of coastal population.