Impact on the Environment:

Cyclones are quite common in the Bay of Bengal and often cause much damage in Bangladesh and coastal areas of West Bengal, Orissa, Andhra Pradesh and Tamil Nadu. Bangladesh has been devastated by cyclones a number of times. In November 1970, a severe cyclone caused a 6 m rise in sea-level and the consequent flooding killed approximately three lakh people.

Another cyclone in 1971 killed more than one lakh people. The cyclone that hit Orissa in 1999, is the worst recorded natural disaster in India. Even an advanced country like America recorded more than 10,000 deaths and huge financial losses when New Orleans was hit by a hurricane named Katrina, during August 2005. Cyclones cause devastation when they hit the landmass in the form of very strong winds, heavy rains and storm tides.

The impact on the environment is severe, some of which are as under (Fig. 18.5):

1. The coastal low lying areas are most affected.

2. The affected areas are inundated both with rainfall and the surge of seawater.

3. Devastation is also increased due to the accompanying high velocity winds.

4. Widespread damage in the form of uprooted trees, blown-off roof tops, standing crops, injuries and death to humans and animals.

5. Many shipwrecks occur during cyclonic storms.

6. The affected areas are impoverished and are followed by spread of epidemic and diseases.

Prevention, Control and Mitigation:

The occurrence of cyclones is a natural phenomenon, over which humans have no control, hence it cannot be prevented. However, some scientists have speculated that rise in global warming may cause an increased occurrences of cyclones. The devastating effects of cyclones can only be controlled and mitigated through some effective policies such as use of advanced technology, hazard reduction initiatives and relief measures.

Use of Advanced Technology:

1. Satellites can easily forecast the origin of cyclones in advance.

2. Satellite images can track the movement and intensity of cyclones.

3. Installation of early warning systems in the coastal areas.

Hazard reduction initiatives:

1. Increasing public awareness regarding cyclones.

2. Increasing the public response to cyclone warnings through training.

3. Development of underground shelter belts in the cyclone prone areas.

Relief measures:

1. Rushing relief to the affected areas in the form of medicines, food, clothes, etc.

2. Checking the spread of epidemic water borne diseases as cyclones are generally accompanied by flooding.

Landslides:

Landslides refer to a rapid down-slope movement of rocks or soil mass under the force of gravity. It is also known as slope failure and mass wasting. Landslides may be typed as mudflow where there is down-slope movement of soil and debris flow, which is the down-slope movement of coarse material and rocks. Landslides may occur when water from rain and melting snow, seeps through the earth on a sloppy surface and encounters a layer of loose, unstable material such as clay.

Landslides mostly occur on unstable hillsides by the action of rain or snow that seep through the soils and rocks (Figs. 18.6 and 18.7). This results in the sliding of earth and rock masses down the hill slopes. These are further triggered due to deforestation and human encroachment on unstable slopes. All the hilly regions of our country are prone to landslides.

The important factors responsible for landslide occurrence are as follows:

1. Stability of slopes

2. The type of earth and rock material

3. The type of vegetation

4. The role of ground water conditions and precipitation

5. Presence of streams, etc.

Avalanche:

It is a type of landslide involving a large mass of snow, ice and rock debris that slides and fall rapidly down a mountainside. Avalanches are initiated when a mass of snow and ice begins to rapidly move downhill because of the overload caused due to a large volume of new snowfall. This result in internal changes of the snow pack, producing zones of weakness along which fissure occurs.