🌀NATURAL HAZARDS AND DISASTER

Disaster

Disaster is an undesirable occurrence resulting from forces that are largely outside human control, strikes quickly with little or no warning, which causes or threatens serious disruption of life and property including death and injury to a large number of people, and requires therefore, mobilisation of efforts in excess of that which are normally provided by statutory emergency services.
Natural forces are not only the causes of disasters, but also they can be caused by human activities. There are some other activities of human beings that accelerate or intensity disasters indirectly. Landslides and floods due to deforestation.

1. Difference between Disaster and Natural Hazard

Natural hazards are elements of circumstances in the natural environment that have the potential to cause harm to people or property or both. These may be swift or permanent aspects of the respective environmental setting like currents in the oceans.
As compared to natural hazards, disasters, which are caused by natural forces or activities of human beings, are relatively sudden and cause large scale, widespread death, loss of property and disturbance to social life.
Natural hazards may be swift or permanent aspects of the respective environmental settings like currents in the ocean , steep slope and unstable structural features in the Himalayas or extreme climatic conditions in deserts or glaciated areas.
Any event can be classed as disaster when the magnitude of destruction and damage caused by it is very high.
Every disaster is unique in terms of the local socio-economic factors that control it, the social response it generates and the way each social group negotiates with it. This opinion indicates three important facts. They are: (i). The magnitude, intensity, frequency and damages caused by natural disasters have increased over the years. (ii). There is a growing concern among people the world over to deal with the menace created by these so that the loss of human life and property can be minimised. (iii). Significant changes have taken place in the pattern of natural disasters over the years.

Modern changes in the perception of natural hazards and disasters:

(i). Previously hazards and disasters were seen as two closely associated and interrelated phenomena i.e. areas prone to natural hazards, were more vulnerable to disasters. Hence people avoided intensification of their activities in such areas and that is how disasters were less damaging.
(ii). Technological power has given large capacity to human intervention in nature.
(iii). Consequently, now, human beings tend to intensify their activities into disaster prone areas increasing their vulnerability to disasters.

2. Yokohama Strategy and Plan of Action for a Safer World

All the member states of the United Nations and other states met at the World Conference on Natural Disaster Reduction in the city of Yokohama from May 23rd-27th 1994.
The resolution of the World Conference on Natural Disasters Reduction are:

(i). It will note that each country has the sovereign responsibility to protect its citizens from natural disasters.
(ii). It will give priority attention to the developing countries, particularly the least developed, landlocked countries and small-island developing states.
(iii). It will develop and strengthen national capacities and capabilities and, where appropriate, national legislation for natural and other disaster prevention, mitigation and preparedness, including the mobilisation of non-governmental organisations and participation of local communities.
It will promote and strengthen sub-regional, regional and international cooperation in activities to prevent, reduce and mitigate natural and other disasters, with particular emphasis on:

(a). Human and institutional capacity-building and strengthening.
(b). Technology sharing: The collection, the dissemination and utilisation of information; and
(c). Mobilisation of resources.

(iv). It also declared the decade 1990-2000 as the International Decade for Natural Disaster.

Classification Of Natural Disasters

Human beings the world over have experienced disasters and have faced and lived with them. Now people are becoming aware and various steps have been initiated at different levels for mitigating the effects of disasters.

India is one of those countries which has experienced most of the natural disasters Every year it loses thousands of lives and property worth millions of rupees due to these natural calamities

Atmosphere

Blizzards

Thunderstorms

Lightning

Tornadoes

Tropical Cyclone

Drought

Hailstorm

Frost, Heat Wave or

Loo. Cold Waves, etc.

Terrestrial

Earthquakes

Volcanic Eruptions

Landslides

Avalanches

Subsidence

Soil Erosion

Aquatic

Floods

Tidal Waves

Ocean Currents

Storm Surge

Tsunami

Biological

Plants and Animals as colonisers (Locusts, Etc).

Insects infestation-fungal, bacterial and

viral diseases such as bird flu, dengue, etc.

Natural Disasters and Hazards in India

1. Earthquake

Earthquakes that are of tectonic origin have proved to be the most devastating and their area of influence is also quite large.
These earthquakes result from a series of earth movements brought about by a sudden release of energy during the tectonic activities in the earth‘s crust.
As compared to these, the earthquakes associated with volcanic eruption, rock fall, landslides, subsidence, particularly in the mining areas, impounding of dams and reservoirs, etc. have limited area of influence and the scale of damage.
Indian plate is moving at a speed of one centimetre per year towards the north and north- eastern direction and this movement of plates is being constantly obstructed by the Eurasian plate from the north.
As a result of this, both the plates are said to be locked with each other resulting in accumulation of energy at different points of time.
Excessive accumulation of energy results in building up of stress, which ultimately leads to the breaking up of the lock and the sudden release of energy causes earthquakes along the Himalayan arch.
Some of the most vulnerable states are Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and the Darjeeling and subdivision of West Bengal and all the seven states of the northeast.
Recently, some earth scientists have come up with a theory of emergence of a fault line and energy build-up along the fault line represented by the river Bhima (Krishna) near Latur and Osmanabad (Maharashtra) and the possible breaking down of the Indian plate.
National Geophysical Laboratory, Geological Survey of India, Department of Meteorology, Government of India, along with the recently formed National Institute of Disaster Management, divided the following five earthquake zones:

- Very high damage risk zone
- High damage risk zone
- Moderate damage risk zone
- Low damage risk zone
- Very low damage risk zone.

(a). Socio-Environmental Consequences of Earthquakes

It becomes a calamity when it strikes the areas of high density of population.
It not only damages and destroys the settlements, infrastructure, transport and communication network, industries and other developmental activities but also robs the population of their material and socio-cultural gains that they have preserved over generations.
It renders them homeless, which puts an extra-pressure and stress, particularly on the weak economy of the developing countries.

(b). Effects of Earthquake

Earthquakes also have some serious and far-reaching environment consequences. Earthquakes are also responsible for landslides and often these cause obstruction in the formation of reservoirs.

- On ground are: Fissures, Settlements, Landslides, Liquefaction, Earth Pressure, and Possible Chain-effects.
- On manmade structures are: cracking, sliding, overturning, buck ling, collapse and possible chain effects.
- On water are: waves, hydro-dynamic pressure, tsunami and possible chain effects.

(c). Earthquake Hazard Mitigation

Methods to decrease the effects of Earthquake are:

- Establishing earthquake monitoring centres (seismological centres) for regular monitoring and fast dissemination of information among the people in the vulnerable areas. Use of Geographical Positioning System (GPS) can be of great help in monitoring the movement of tectonic plates.
- Preparing a vulnerability map of the country and dissemination of vulnerability risk information among the people and educating them about the ways and means minimising the adverse impacts of disasters.
- Modifying the house types and building designs in the vulnerable areas and discouraging construction of high-rise buildings, large industrial establishments and big urban centres in such areas.
- Finally, making it mandatory to adopt earthquake-resistant designs and use light materials in major construction activities in the vulnerable areas.

2. Tsunami

Earthquakes and volcanic eruptions that cause the sea-floor to move abruptly resulting in sudden displacement of ocean water in the form of high vertical waves are called tsunamis (harbour waves) or seismic sea waves.
Normally, the seismic waves cause only one instantaneous vertical wave; but, after the initial disturbance, a series of after waves are created in the water that oscillate between high crest and low trough in order to restore the water level.
Formation of Tsunami : The speed of wave in the ocean depends upon the depth of water. It is more in the shallow water than in the ocean deep. As a result of this, the impact of tsunami is less over the ocean and more near the coast where they cause large-scale devastations. Therefore, a ship at sea is not much affected by tsunami and it is difficult to detect a tsunami in the deeper parts of sea. Thus, these are also called Shallow Water Waves.
Regions affected by Tsunami : Tsunamis are frequently observed along the Pacific ring of fire, particularly along the coast of Alaska, Japan, Philippines, and other islands of South- east Asia, Indonesia, Malaysia, Myanmar, Sri Lanka, and India etc.
Effects of Tsunami : After reaching the coast, the tsunami waves release enormous energy stored in them and water flows turbulently onto the land destroying port cities and towns, structures, buildings and other settlements. The effect of tsunami is more along the coast because the density of population is high.
Mitigation : It is beyond the capacity of individual state or government to mitigate the damage. Hence, combined efforts at the international levels are the possible ways of dealing with these disasters. India has volunteered to join the International Tsunami Warning System after the December 2004 tsunami disaster.

3. Tropical Cyclone

Tropical cyclones are intense low-pressure areas confined to the area lying between 30° N and 30° S latitudes, in the atmosphere around which high velocity winds blow.
Horizontally, it extends up to 500-1,000 km and vertically from surface to 12-14 km.
A tropical cyclone or hurricane is like a heat engine that is energised by the release of latent heat on account of the condensation of moisture that the wind gathers after moving over the oceans and seas.
Some initial conditions for the emergence of a tropical cyclone are:

- Large and continuous supply of warm and moist air that can release enormous latent heat.
- Strong Coriolis force that can prevent filling of low pressure at the centre (absence of Coriolis force near the equator prohibits the formation of tropical cyclone between (0°-5°latitude).
Unstable condition through the troposphere that creates local disturbances around which a cyclone develops.
Finally, absence of strong vertical wind wedge, which disturbs the vertical transport of latent heat.

(a). Structure of Tropical cyclone

Tropical cyclones are characterised by large pressure gradients. The centre of the cyclone is mostly a warm and low-pressure, cloudless core known as the eye of the storm.
Generally, the isobars are closely placed to each other showing high-pressure gradients.

(b). Spatio-temporal Distribution of Tropical Cyclone in India

The tropical cyclones in India originate in the Bay of Bengal in the east and the Arabian Sea in the west.
Though most of the cyclones originate between 10°-15° north latitudes during the monsoon season, yet in case of the Bay of Bengal, cyclones mostly develop during the months of October and November.
Originate between 16°-2° N latitudes and to the west of 92° E.
By July the place of origin of these storms shifts to around 18°N latitude and west of 90°E near the Sunder ban Delta.

(c). Consequences of Tropical Cyclones

The energy to the tropical cyclone comes from the latent heat released by the warm moist air.
In India, the force of the cyclone decreases with increase in distance from the Bay of Bengal and the Arabian Sea. So, the coastal areas are often struck by severe cyclonic storms with an average velocity of 180 km/h. Often, this results in abnormal rise in the sea level known as Storm Surge which causes destruction.

4. Floods

Floods occur commonly when water in the form of surface run-off exceeds the carrying capacity of the river channels and streams and flows into the neighbouring low-lying flood plains.
Causes of Floods : Floods occur when a river bursts its banks and the water spills onto the floodplain. Flooding tends to be caused by heavy rain- the faster the rainwater reaches the river channel, the more likely it is to flood.
Regions affected by Floods are South, Southeast and East Asian countries, particularly in China, India and Bangladesh are frequent and equally disastrous.
Rashtriya Barh Ayog (National Flood Commission) identified 40 million hectares of land as flood prone in India. Areas of India frequently affected by floods are Assam, West Bengal and Bihar are among the high flood prone states of India. Apart from these, most of the rivers in the northern states like Punjab and Uttar Pradesh are also vulnerable to occasional floods.
States like Rajasthan, Gujarat, Haryana and Punjab are also getting inundated in recent decades due to flash floods. Tamil Nadu experiences flooding during November- January due to the retreating monsoon.

(i). Consequences and Control of Floods

Floods have serious consequences on the national economy and society.
Floods do not only destroy valuable crops every year but these also damage physical infrastructure such as roads, rails, bridges and human settlements.
Spread of diseases like cholera, gastro-enteritis, hepatitis and other water-borne diseases spread in the flood-affected areas.
Majuli (Assam), the largest riverine island in the world, is the best example of good paddy crops after the annual floods in Brahmaputra. But these are insignificant benefits in comparison to the grave losses.
Methods to control the floods : Construction of flood protection embankments in the flood-prone areas, construction of dams, afforestation and discouraging major construction activities in the upper reaches of most of the flood-creating rivers, etc. Removal of human encroachment from the river channels and depopulating the flood plains can be the other steps. Cyclone centres may provide relief in coastal areas which are hit by a storm surge.

5. Droughts

The term 'drought‘ is applied to an extended period when there is a shortage of water availability due to inadequate precipitation, excessive rate of evaporation and over-utilisation of water from the reservoirs and other storages, including the groundwater.
Drought is a complex phenomenon as it involves elements of meteorology like precipitation, evaporation, evapo-transpiration, ground water, soil moisture, storage and surface run-off, agricultural practices, particularly the types of crops grown, socio-economic practices and ecological conditions

Types of Droughts

Meteorological Drought : It is a situation when there is a prolonged period of inadequate rainfall marked with mal-distribution of the same over time and space.
Agricultural Drought : It is also known as soil moisture drought, characterized by low soil moisture that is necessary to support the crops, thereby resulting in crop failures. Moreover, if an area has more than 30 percent of its gross cropped area under irrigation, the area is excluded from the drought-prone category.
Hydrological Drought : It results when the availability of water in different storages and reservoirs like aquifers, lakes, reservoirs, etc. falls below what the precipitation can replenish.
Ecological Drought : When the productivity of a natural ecosystem fails due to shortage of water and as a consequence of ecological distress, damages are induced in the ecosystem.

Drought Prone Areas In India

Droughts and floods are the two accompanying features of Indian climate.
About 30 percent of the country’s total area is identified as drought prone affecting around 50 million people.
It is a common sight to witness that one region suffers due to floods in one season and experiences drought in the other. This is mainly because of the large-scale variations and unpredictability in the behaviour of the monsoon in India.
On the basis of severity of droughts, India can be divided into the following regions:

(a) Extreme drought affected areas: Most parts of Rajasthan, particularly areas to the west of the Aravali hills, i.e. Marusthali and Kachchh regions of Gujarat fall in this category. Included here are also the districts like Jaisalmer and Barmer from the Indian desert that receive less than 90mm average annual rainfall.
(b) Severe drought prone areas: Parts of eastern Rajasthan, most parts of Madhya Pradesh, eastern parts of Maharashtra, interior parts of Andhra Pradesh and Karnataka Plateau, northern parts of interior Tamil Nadu and southern parts of Jharkhand and interior Orissa are included in this category.
(c) Moderate drought affected area: Northern parts of Rajasthan, Haryana, southern districts of Uttar Pradesh, the remaining parts of Gujarat, Maharashtra except Konkan, Jharkhand and Coimbatore plateau of Tamil Nadu and interior Karnataka are included.

Consequences of Drought

Crop failure leading to scarcity of food and often shortage in all the three (trikal) is most devastating.
Large-scale death of cattle and other animals, migration of humans and livestock are commonly seen in the drought affected areas.
Scarcity of water compels people to consume contaminated water resulting in spread of many waterborne diseases like gastro-enteritis, cholera, hepatitis, etc.
Droughts have both immediate as well as long-term disastrous consequences on the social and physical environments.
Planning for drought: Provision for the distribution of safe drinking water, medicines for the victims and availability of fodder and water for the cattle and shifting of the people and their livestock to safer places, Identification of groundwater potential in the form of aquifers, transfer of river water from the surplus to the deficit areas, and particularly planning for inter-linking of rivers and construction of reservoirs and dams, etc.
Remote sensing and satellite imageries can be useful in identifying the possible river-basins that can be interlinked and in identifying the ground water potential.
Dissemination of knowledge about drought-resistant crops and proper training to practise the same can be some of the long-term measures that will be helpful in drought-mitigation.
Rainwater harvesting can also be an effective method in minimising the effects of drought.

6. Landslides

Landslides are largely controlled by highly localised factors. Hence, gathering information and monitoring the possibilities of landslide is not only difficult but also immensely cost-intensive.
Controlling factors of landslide are: Geology, geomorphic agents, slope, land-use, vegetation cover, human activities.

(I). Landslide Vulnerability Zones of India

Very high vulnerability zone : Highly unstable, relatively young mountainous areas in the Himalayas and Andaman and Nicobar, high rainfall regions with steep slopes in the Western Ghats and Nilgiris, the north-eastern regions, along with areas that experience frequent ground-shaking due to earthquakes, etc. and areas of intense human activities, particularly those related to construction of roads, dams, etc. are included in this zone.
High vulnerability zone : Areas that have almost similar conditions to those included in the very high vulnerability zone are also included in this category. The only difference between these two is the combination, intensity and frequency of the controlling factors. All the Himalayan states and the states from the north-eastern regions except the plains of Assam are included in the high vulnerability zones.
Moderate to low vulnerability zone : Areas that receive less precipitation such as Trans- Himalayan areas of Ladakh and Spiti (Himachal Pradesh), undulated yet stable relief and low precipitation areas in the Aravali, rain shadow areas in the Western and Eastern Ghats and Deccan plateau also experience occasional landslides. Landslides due to mining and subsidence are most common in states like Jharkhand, Orissa, Chhattisgarh, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Tamil Nadu, Goa and Kerala.

(II). Consequences of Landslides

Landslides have relatively small and localized area of direct influence, but roadblock, destruction of railway lines and channel- blocking due to rock-falls have far-reaching consequences.
Diversion of river courses due to landslides can also lead to flood and loss of life and property.

(III). Mitigation

Restriction on the construction and other developmental activities such as roads and dams, limiting agriculture to valleys and areas with moderate slopes, and control on the development of large settlements in the high vulnerability zones, should be enforced.
Promoting large-scale afforestation programmes, terrace farming and construction of bunds to reduce the flow of water in these area.

Disaster Management

The Disaster Management Bill, 2005, defines disaster as a catastrophe, mishap, calamity or grave occurrence affecting any area, arising from natural or man-made causes, or by accident or negligence which results insubstantial loss of life or human suffering or damage to, and destruction of, environment, and is of such nature or magnitude as to be beyond the coping capacity of the community of the affected area.

Mitigation and Preparedness

There are three stages involved in disaster mitigation and management:
(i) Pre-disaster management : It involves generating data and information about the disasters, preparing vulnerability zoning maps, spreading awareness among the people about the disasters, disaster planning, preparedness and preventive measures are other steps that need to be taken in the vulnerable areas.
(ii). During disasters : Rescue and relief operations such as evacuation, construction of shelters, relief camps, supplying of water, food, clothing and medical aids etc. should be done on an emergency basis.
(iii). Post-disaster operations : It should involve rehabilitation, recovery of victims, concentrate on capacity building in order to cope up with future disasters.

& Comment

Writiy

Wednesday, 15 December 2021

Natural Hazards and Disasters