Dr. J.B. KathiriyaDept. of Veterinary Public Health &

EpidemiologyCollege of Veterinary Science & A.H.,

Junagadh Agricultural University,Junagadh-362001

INTRODUCTIONNatural Calamities like Cyclone, flood, earthquake,

volcanoes and Landslides are normal natural events in the formation of earth, but they are disastrous when they strike human settlements.

In India, natural disasters occur frequently. For example, about 260 million people are being affected by frequent floods which occur in eight major river valleys in 40 million ha..

About ten million people are affected by cyclones in the entire 5700km long coastline of peninsular India in 9 states.

This impact of earthquake is much more than the other disasters because about 400 million people in the seismic zones IV and V (55% of total area of India) are being greatly affected.

About ten million people living along the entire sub Himalayan region and Western Ghats suffer a lot due to landslides.

Since the disasters strike human settlements often in different parts of the world, they have to learn to minimize the effects of disasters.

CYCLONESCyclone is a large scale 

air mass that rotates around a strong center of low atmospheric pressure.

Tropical cyclones in the warm oceans are formed to heat and moisture.

Sea surface temperature should be above 260C. Cyclones move like a spin (120-400 km/hr) with a diameter of 100-1500 km.

Management It is not possible to stop cyclones. But we can

follow certain measures to escape from their devastation. The measures are as follows: Planting of trees along coastal belts. Construction of dams and wind breaks. Installation of wide roads for the people to

evacuate quickly in emergencies. Installation of better working system. Construction of proper drainage. Disaster prediction i.e., announcement of cyclone

warning to people would help in minimizing the impact.  

FLOODSCauses It is caused by natural and human factors. Natural Factors: Heavy and prolonged rainfall,

blocking of free flow of the rivers due to landsides and overflowing of river banks.

Human Factors: Building activities, channel manipulation through diversion of river course, construction of bridges, deforestation,

changes in land use and blockage of water courses by plastics.

Recently in Chennai, the intensity of flooding of roads and residential colonies increased due to the accumulation of plastics in water courses.

Control The impact of flood can be minimized by the

following steps The discharge of waste must be hastened. The flow of water must be diverted. The return runoff water from river must be delayed. The flood situation must be announced to the

people in advance through media.

EARTHQUAKESA sudden movement of Earth’s crust (or) a motion of the

ground surface is known as earthquake. Earth’s crust has many tectonic plates of solid rock which

slowly move along their boundaries. Hypocenter is a point of sudden energy release. Epicenter is the place on the ground surface (fault lines or

planes of weakness) recording seismic waves (first movement) for the first time.

The intensity of energy released by an earthquake is measured by the Richter scale devised by Charles F. Richter.

Sesimometer is an instrument used to measure seismic waves.

Severity of an earthquake

S. No Richter Scale

Severity of Earth quake

1. Less than 4 Insignificant 2. 4-4.9 Minor 3. 5-5.9 Damaging 4. 6-6.9 Destructive 5. 7-7.9 Major 6. More than

8.9 Great

CausesNatural factors: Friction due to moving of

tectonic plates creates stress which leads to fractures and causes earthquakes.

Human factors: Underground nuclear testing causes earth tremor. Collection of huge amount of water behind a dam also

causes earthquake. Pouring liquid wastes into deeper wells creates tremor.

Effects Earthquake causes damage to buildings, roads,

factories, dams and bridges. Water supply and electricity supply and

Telecommunication are completely disrupted. In hilly areas, land slides occur damaging dams

and causing floods

Mitigation of earthquakes By constructing earthquake resistant

buildings or by making pads or floats beneath the buildings we can reduce the impact of earthquake.

By making wooden houses in seismic zones, the effects of earthquake can be mitigated.  

Tusnamis-(High Sea waves) (Japanese word) Severe earthquakes under sea water generate

high sea waves and these are referred to as tsunami in Japanese language.

They travel at a speed up to 1000mk/hr or more. They rise from 15 meters to 65 meters in height

at sea shore, causing vast devastation in coastal areas.

The first Tsunami hit India in 1945, when Indians were engaged in the war of Independence.

At that time, people did not worry about Tsunami much. Even now there is a danger of Tsunami in the Arabian sea.

People are not aware of this danger. But the animals are capable of learning the tsunami strike in advance with the help of their ultrasonic radiation.

Thus, they often escape from the danger. Therefore, it is better to train sea animals as done in China, in order to caution the human beings about tsunami in advance.

A tsunami-warning instrument is to be fixed in the Bay of Bengal to track tsunami in advance.

Generally tsunami strikes during the beginning or towards the end of a month. For example, tsunamis struck on 27th August 1883, 25th November 1945 and 26th December 2004. In some countries, tsunami struck in the beginning of the month.

LANDSLIDESThe moving down of coherent rock of soil mass due to

gravitation is called landslide. The sudden rockslides are more

Causes Human activities like hydroelectric Projects, dams,

construction of roads, railway lines, mines and deforestation cause landslides.

Mitigation Landslides can be minimized by stabilizing the slopes by

adopting the following measures: A forestation in vulnerable areas so that vegetation

consolidates the slope materials and provides cohesion with the help of root and also retards water flow and erosion.

Providing slope supported by wired stone blocks. Providing concrete support at the base of slope. Draining the surface and subsurface water.