Friday, January 30, 2015

Floods in India

The Indian subcontinent is highly vulnerable to a number of natural disasters.
Droughts, Floods, Cyclones and Earthquakes are natural disasters in the
country though Landslides, Avalanches and bush fire also occur in most of the states of the Himalayan region.

Due to unique and widely varying geographical and geological conditions of the
India, virtually all types of natural disasters take place with various intensities
and in different regions.

Floods occur when large volume of water from heavy rainfall and/or river overflow canals and is not able to drain quickly through normal channels. Floods are the most frequent and widespread natural disasters resulting in death, destruction, degradation and displacement. Whether sudden onset or slow development, floods take long to subside and they leave prolonged damage.

India is the second most flood affected country where flood is a common national disaster especially during the later part of the monsoon period. Severe floods occur almost every year in one part of the country or the other causing loss of life, large scale damage to property and untold misery to millions of people.

Floods are estimated to affect 6.7 million hectares of land annually. The effects of flood on the affected population are:
1. inundation marooning,
2. drowning,
3. loss of habitat, roads, communications,
4. destruction of crops,
5. industrial shutdown,
6. diarrohea diseases, respiratory infections etc.
Most of the affected population is among the poorer sections.

In India the most affected states due to floods are Bihar, Assam, Uttar Pradesh, the states in the northeast, Orrisa & West Bengal. Floods cause serious damage in states like Andhra Pradesh, Gujarat, Haryana, Punjab, Rajasthan & Tamil Nadu.

To control floods:
- Rashtriya Barh Ayog was established in 1976 and
-Task force on flood management & soil erosion was setup in 2004

Primary responsibility of flood control rests with with state Governments.

Structural measures for flood management include:
-Flood embankments
-Dams & Reservoirs
-Natural detention basins
-Channel improvement
-Drainage improvement
-Diversion of flood waters
-Afforestation
-Catchment Area Treatment
-Anti-erosion works

Non-structural measures include:
-Flood plain zoning & flood proofing
-Flood preparedness & community level awareness
-Flood forecasting & early warning system
-Afforestation
-Public relief and flood insurance

Increased vulnerability due to floods occurs due to:
-Indiscriminate encroachment
-Increasing economic and developmental activity in flood plains
-Lack of regulations
-Inadequate maintenance
-Inadequate drainage
-Lack of disaster preparedness

Flood management strategies
Flood forecasting and warning steps involve:
-Data collection of hydrological data including river water level and river discharge
-Data collection of hydrometeorological data including rainfall and other precipitation like hail, snow, etc..
-Wireless. telephone, fax, satellite, telegraph, etc
-Correlation, mathematical models
-Civil authorities, Press, AIR, Doordarshan, other users, local representatives

-Flood plain zoning is an important non-structural resource. It regulates land use in flood plains to restrict damage by floods. It involves demarcation by zones in flood plains compatible with flood risks involved.
-The floor of lowest storey of buildings should be raised above the normal minimum flood level of adjoining land.
-People living in flood banks should be shifted to other places.
-Road side drains should be provided to rain drain water from urban areas.

What is disaster management


Tsunami








Disaster Management Continuum


National Disaster Management Structure


Avalanche

Avalanche is a rapid movement of snow down a slope triggered either naturally or by human activity. This occurs typically in mountain terrain. Avalanches are divided into four classes:
1. Dry powder avalanches
2. Wet new snow avalanches
3. Snow slabs or Wind slabs and
4. Wet old snow avalanches.

Cyclones

Spiral movement of winds towards a low pressure centre is called a cyclone. Storms associated with low pressure and rising winds are called cyclonic storms. The movement of wind in a cyclone is counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere.
if the wind speed exceeds 73 miles/hr, then it is called a cyclone
if the wind speed is less than 39 miles/hr then it is called a tropical depression and if the wind speed lies between 39 and 73 miles/hr it is called a storm.

control measures of a cyclone:
1. meteorological information should be given to people as soon as possible.
2. Development activities should be minimised along the frequently affected areas.
3. Modified construction techniques should be adopted to suit buildings in frequently affected areas.

Cyclone is a type of rotating storm that occurs over the seas and oceans near the tropic. A tropical cyclone is a storm system characterized by a large low pressure centre and numerous thunderstorms that produce strong winds and heavy rains. India has a long coastline and the second highest number of people in the world exposed to tropical cyclones. Cyclones strike India in May-June and October-November coinciding with the onset and retreat of monsoon. Coastal Andhra Pradesh, Odhisha, Tamil Nadu and Sunderbans of West Bengal are the major cyclone prone areas of India.

The Odhisha Super cyclone in october 1999 was one of the worst cyclones with wind velocities as high as 350 kmph. Cyclones are generally associated with sea surges, when sea level rises upto 7m. Cyclones are associated with heavy rains. The following factors lead to formation of cyclones:
1. Location and temperature are vital for the formation of cyclones
2. The location must be 5 to 15 degrees latitude on either side of the equator over oceans or seas.
3. The surface temperature of seas or oceans must be more than 26.5 C or above
4. Depression with convection current starts to gather clouds.

Cyclones are easy to predict. The Indian Meteorological Department (IMD) continuously monitors for any low pressure developing in the atmosphere above the ocean using radar. Advanced technology is used to predict the intensity of the cyclonic storm and the coastal area to be hit by any potential cyclone. The large belt along the east coast of India is prone to cyclones and the west coast is also prone to cyclones.