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.

Natural Disasters - Hydrometeorological based disasters

Tropical cyclones:
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain.
It is known by different names in different parts of the world.
Tropical cyclones have a geographic origin. They form mostly over tropical seas .They are called cyclones as they have winds blowing counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. The opposite direction of winds is due to the "coriolis effect"
Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface. This water vapour condenses as clouds and falls on Earth as rain when it gets saturated.
Cyclones generate high waves, storm surge and very strong winds. Coastal regions are particularly vulnerable to damage from a cyclone. Heavy rains cause flooding inland while storm surges can cause coastal flooding.
The effect of cyclones on human population is devastating. It has caused loss of life and property since time immemorial.
Tropical cyclones are areas of low pressure.The environment near the center of tropical cyclones is warmer than the surroundings and is called as "warm core". The near-surface wind field of a tropical cyclone is characterised by air rotating rapidly around a centre of circulation while also flowing radially inwards. As air flows radially inward, it begins to rotate cyclonically  in order to conserve angular momentum. Towards the centre, the air begins to rise . Wind speeds are low at the centre and begin to increase rapidly moving outwards. The wind speeds decrease gradually with increasing radii.
There are six Regional Specialized Meteorological Centers (RSMCs) worldwide. These organizations are designated by the World Meteorological Organization and are responsible for tracking and issuing bulletins, warnings, and advisories about tropical cyclones in their designated areas of responsibility. In addition, there are six Tropical Cyclone Warning Centers (TCWCs) that provide information to smaller regions
Worldwide, tropical cyclone activity peaks in late summer, when the difference between temperatures aloft and sea surface temperatures is the greatest. However, each particular basin has its own seasonal patterns. On a worldwide scale, May is the least active month, while September is the most active month. November is the only month in which all the tropical cyclone basins are active.
Most tropical cyclones form in a worldwide band of thunderstorm activity near the equator
The 1990 Andhra Pradesh cyclone or the 1990 Machilipatnam Cyclone was the worst disaster to affect Southern India since the 1977 Andhra Pradesh cyclone. It was first noted as a depression on May 4, 1990. It rapidly intensified into a super cyclonic storm (IMD scale, code named BOB 01) on May 8th. It was given a "category 4" storm on the saffir-simpson scale. The highest wind speeds recorded were greater than 200 kmph.
The storm resulted in the death of nearly 1000 people, 1 lakh animals and estimated samage to crops exceeding 600 million USD.
Cyclonic Storm Nilam  (IMD designation: BOB 02) was the deadliest tropical cyclone to directly affect South India since Cyclone Jal in 2010. Originating from an area of low pressure over the Bay of Bengal on October 28, the system began as a weak depression. northeast of Trincomalee, Sri Lanka. Over the following few days, the depression gradually intensified into a deep depression, and subsequently a Cyclonic Storm by October 30. It made landfall near Mahabalipuram on October 31 as a strong Cyclonic Storm with peak winds of 85 km/h.  In Chennai's Marina Beach, strong winds pushed piles of sand ashore and seawater reached nearly a 100 m (330 ft) inland. Schools and colleges in the city remained closed for more than three days.
More than 3000 people were evacuated around Mahabalipuram in the wake of the storm. Schools and colleges in Chennai declared holidays until November 1 as 282 schools had been converted into relief centers. Government offices and private organisations closed their operations early to ease traffic congestion. Cyclone shelters had been arranged in Nagapattinam and Cuddalore districts. Mahabalipuram faced power outages and several trees were uprooted and huts were damaged. While damages to property were considerable, human casualties were very few 

Search for tropical cyclones in google / wikipedia
List of cyclones in India (Phalin, etc)

Floods:



Droughts:

Introduction to Disaster Management

A disaster is a serious disruption of the functioning of a community or a society involving widespread human, material, economic or environmental losses and impacts, which exceeds the ability of the affected community or society to cope using its own resources.

Developing countries suffer the greatest costs when a disaster strikes.
Hazards are broadly divided into natural or human-made disasters.

A Natural Hazard is a natural process or phenomenon that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage. Natural disasters like earthquakes, landslides, volcanic eruptions, floods, hurricanes, tornadoes, blizzards, tsunamis, and cyclones are all natural hazards that kill thousands of people, destroy habitat and property each year.However, the rapid growth of the world's population and its increased concentration often in hazardous environments has escalated both the frequency and severity of disasters. With the tropical climate and unstable land forms, coupled with deforestation, unplanned growth proliferation, non-engineered constructions make the disaster-prone areas more vulnerable, tardy communication, poor or no budgetary allocation for disaster prevention, developing countries suffer more or less chronically by natural disasters. Asia tops the list of casualties caused by natural hazards.

Human-Induced disasters are the consequence of technological hazards. Examples include stampedes, fires, transport accidents, industrial accidents, oil spills and nuclear explosions/radiation. War and deliberate attacks may also be put in this category.

Man-made hazards are events that have not happened, for instance terrorism. Man-made disasters are examples of specific cases where man-made hazards have become reality in an event.

The United Nations General Assembly designated the 1990s as the International Decade for Natural Disaster Reduction (IDNDR).

Its basic objective was to decrease the loss of life, property destruction and social and economic disruption caused by natural disasters, such as earthquakes, tsunamis, floods, landslides, volcanic eruptions, droughts, locust infestations, and other disasters of natural origin.

An International Decade for Natural Disaster Reduction, beginning on 1 January 1990, was launched by the United Nations, following the adoption of Resolution on 22 December 1989. The decade was intended to reduce, through concerted international action, especially in developing countries, loss of life, poverty damage and social and economic disruption caused by natural disasters. To support the activities of the decade, a Secretariat was established at the United Nations Office in Geneva, in close association with UNDRO.

An increase in global industrial activity coupled with population growth and increased fossil fuel consumption has led to the following problems:
-Destruction og green lungs of the earth
-Increased agricultural activity
-Use of toxic pesticides
-Increased green house gases in the atmosphere
-Pollution of air, water and soil
-Acid rain
-Creation of Ozone hole
-Global warming and
-Climate change

There is an increasing trend in the frequency and intensity of both natural & man made disasters. Thic can be attributed to:
-Population explosion
-Rapid industrialization
-Urbanization
-Global warming and
-Environmental pollution