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❶As a result of all these factors, the silt load of many rivers has increased greatly. Relief food donation and distribution to the people is also necessary.

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The IMD has published the tracks of the cyclones since and updates them every year in its quarterly scientific journal, Mausam. As 90 per cent of the deaths in severe cyclones all over the world occur in high storm surges accompanying them, the only feasible method to save the lives of human beings and animals is to evacuate them to safe inland cyclone shelters as early as possible after the receipt of advance cyclone warnings from the IMD.

The evacuation of people is difficult in flat coastal districts as in Bangladesh where the tides of six to 10 metres above the sea level submerges offshore islands and travels inland for considerable distances. This is a narrow belt at the equator, where the trade winds of the two hemispheres meet. It is a region of high radiation energy which supplies the necessary heat for the vaporisation of sea water into the air.

This moist unstable air rises, generates convective clouds and leads to an atmospheric disturbance with a fall in surface atmospheric pressure. This causes a convergence of surrounding air towards this region of low pressure. The converging mass of air gains a rotary motion because of what is known as the Coriolis force caused by the rotation of the Earth. However, under favourable circumstances, such as high sea-surface temperatures, this low pressure area can get accentuated.

The convective instability builds up into an organised system with high-speed winds circulating around the low pressure interior. The eye has an average radius of 20 to 30 km. It can even be as much as 50 km. Given the existing scientific knowledge about cyclones, it is not yet possible to physically dissipate the buildup of a massive cyclone.

Cures are generally worse than the disease. For example, while seeding by sodium iodide crystals has been attempted in some parts of the world— with marginal success—a more effective prescription proposed sometimes is a nuclear explosion.

Obviously, that would be trading one disaster for an even greater one. Accepted technology, therefore, only provides the capability to detect and track cyclones with sophisticated satellite imagery and ground- based radar systems. But here too the limitations are glaring. Atmospheric science, for example, is not yet in a position to unambiguously predict the motion and behaviour of a cyclone more than 24 hours ahead of its arrival.

So all that is possible in that brief span is to warn the vulnerable sections of the population of the imminent danger and adopt measures to move them to safer cyclone withstanding structures.

The frequency, intensity and coastal impact of cyclones varies from region to region. Interestingly, the frequency of tropical cyclones is the least in the north Indian Ocean regions of the Bay of Bengal and the Arabian Sea; they are also of moderate intensities. But the cyclones are deadliest when they cross the coast bordering North Bay of Bengal coastal areas of Orissa, West Bengal and Bangladesh. This is mainly due to storm surges tidal waves that occur in this region inundating the coastal areas.

Over the last two-and-a-half centuries, 17 of the 22 severe tropical cyclones—each causing loss of more than 10, human lives—took place in the North Bay of Bengal. While gales and strong winds, as well as torrential rain, that usually accompany a cyclone can cause sufficient havoc to property and agriculture, loss of human life and cattle is mainly due to storm surges. If the terrain is shallow and shaped like a funnel, like that of Bangladesh—much of the exposed land is just about at the mean sea level or even less—storm surges get enormously amplified.

Coastal inundation due to a combination of high tide and storm surge can cause the worst disaster. India has an efficient cyclone warning system. Tropical cyclones are tracked with the help of i regular observation from weather network of surface and upper air observation stations, ii ships report, iii cyclone detection radars, iv satellites, and v reports from commercial aircraft.

Ships of merchant fleet have meteorological instruments for taking observations at sea. The range of these radars is km. When the cyclone is beyond the range of coastal radars, its intensity and movement is monitored with weather satellites.

Warnings are issued by the area cyclone warning centres located at Kolkata, Chennai and Mumbai, and cyclone warning centres at Bhubaneswar, Visakhapatnam and Ahmedabad.

This consists of the following elements:. Typically, in a cyclone the maximum devastative effects are within about km from the centre and on the right of the storm track where all the islands lie. Evacuating the population just 24 hours before would require an army of high speed boats, an unfeasible proposition for a resource—poor country.

The obvious solution, therefore, would be to provide a large number of storm shelters in the particularly vulnerable areas.

So inured are we to the annual phenomena of floods in season, that one more village practically washed away by a flash flood causes no more than a ripple. But for the people there it is a traumatic experience. Earlier, it used to be done by a conventional method—gauge to gauge or discharge correlation by which future gauges at forecast points are estimated on the basis of gauge discharge observed at some upstream station. Gradually, other parameters like precipitation, etc. Nowadays, computer-based hydrological models are being used for inflow and flood forecasting.

The basic information required for flood forecasting is rainfall data of the catchment area of the river. Due to poor communication and inaccessibility, complete information is not always available. However, with sophisticated high-powered S-band radars, it is now possible to estimate the rainfall in an area of up to km around the radar site.

This system is used extensively in the US for estimating the rainfall potential in the catchment areas of major rivers an issue of flood forecast warning. The use of radar for the precipitation estimate is based on the principle that the amount of echo return from a volume of cloud depends on the number and size of hydrometeros in it. The empirical relationship between the echo return and the rainfall rates has been developed for various types of rain.

Using fast switching digital circuits, the return video is digitised, integrated, normalised and contoured into standard six or seven rainfall rates. Observations taken every ten minutes can be cumulatively added and averaged to give hour rainfall prediction over the region.

Through appropriate modes, the information from a number of radar sites can be sent to a central office where powerful computers process the data and yield the overall rainfall potential of the weather system. The advantage of using radars for hydrological work lies in the fact that the information over the inaccessible region is available without actual human intervention. Of course, there are many assumptions which do not always hold good, thereby introducing large errors in the result.

But with suitable calibration with actual gauge measurements correction factors could be applied. This has not helped much as population has moved into areas where flooding used to occur and has been controlled due to structure. Whenever flooding level is higher than what the structure can hold, the result is devastating. The non-structural approach calls for removing populations from the flood plains.

Another important aspect is to reduce the silting of rivers. Afforestation in the catchment areas, along the river banks, helps in maintaining the effective river volume.

But it is evident that, over the last four decades or so, flood control efforts have proved counter-productive because they have not included adequate planning for conservation of watersheds.

As a result the increasing siltation of rivers is accelerating their rate of flow in flood, eventually forcing even well built embankments to give way. As is well known, embankments increase the force of the river by channelling it over a narrow area instead of permitting it to spread.

The danger of relying too heavily on the system of embankments for flood control has been well documented. Apart from the depletion in forest cover, overgrazing contributes greatly to soil loss in the catchment areas.

Even in the mountainous areas, where efforts have been made to plant trees on steep slopes to reduce the soil loss during rains, mountain goats have impeded the process of regeneration. Cattle and goats also destroy the plant cover that springs up after the rain which is crucial for holding down the soil. Human activity is yet another factor. Quarrying, road construction, and other building activity in sensitive catchment areas add to the soil loss.

As a result of all these factors, the silt load of many rivers has increased greatly. The siltation level of dams, which has generally been underestimated at the time of construction has had to be revised by 50 to per cent in some cases. Siltation reduces the capacity of reservoirs. Consequently in order to save the dam, unscheduled and panic releases of water are resorted to often without giving adequate warning to people downstream who live in the path of the released water.

Thus ironically dams built partly to assist in flood control, are today contributing to the devastation caused by floods. The phenomenon that really ought to engage the minds of planners is how and why the flood-prone area in the country is increasing each year. Even areas which have never known floods in the past are now affected. The NFC estimates that 40 million hectares are flood-prone of which 32 million hectares can be protected.

Some such Centrally-sponsored schemes are: The Central government provides special assistance to the Border States and north eastern states for taking up some special priority works. A tsunami is a series of travelling ocean waves which are set off by geological disturbances near the floor of the ocean. The waves of very, very long wavelengths and period rush across the ocean and increase their momentum over a stretch of thousands of kilometers.

Some tsunamis may appear as a tide but they are not tidal waves in reality. While tides are caused by gravitational influences of the moon, sun and the planets, tsunamis are seismic sea waves. That is, they are related to an earthquake- related mechanism of generation. Tsunamis are usually a result of earthquakes, but may be at times caused by landslides or volcanic eruption or, very rarely, a large meteorite impact on the ocean. The tsunami can be understood at the basic level by looking at the series of concentric ripples formed in a lake when a stone is thrown into it.

A tsunami is like those ripples but caused by a disturbance much greater in magnitude. Tsunamis are shallow-water waves different from the wind-generated waves which usually have a period of five to twenty seconds which refers to the time between two successional waves of about to metres. They have a period in the range of ten minutes to two hours and a wavelength exceeding km. The rate of energy loss of a wave is inversely related to its wavelength. So tsunamis lose little energy as they propagate as they have a very large wavelength.

So they will travel at high speeds in deep waters and travel great distances as well losing little energy. A tsunami that occurs metres deep in water has a speed of km per hour. At m, it travels at Ion per hour. It travels at different speeds in water: As an average ocean depth of m is assumed, one talks of tsunamis as having an average speed of about km per hour.

The long gravity tsunami waves are caused by two interacting processes. There is the slope of the sea surface which creates a horizontal pressure force. Then there is the piling up or lowering of sea surface as water moves in varying speeds in the direction that the wave form is moving. These processes together create propagating waves.

A tsunami can be caused by any disturbance that displaces a large water mass from its equilibrium position. An undersea earthquake causes buckling of the sea floor, something that occurs at subduction zones, places where drifting plates that constitute the outer shell of the earth converge and the heavier oceanic plate dips below the lighter continents.

As a plate plunges into the interior of the earth it gets stuck against the edge of a continental plate for a while, when stresses build up, then the locked zone gives way. Parts of the ocean floor then snap upward and other areas sink downward. In the instant after the quake, the sea surface shape resembles the contours of the seafloor. But then gravity acts to return the sea surface to its original shape. The ripples then race outward and a tsunami is caused.

There were 17 tsunamis in the Pacific from to which resulted in 1, deaths. During a submarine landslide, the equilibrium sea-level is altered by sediment moving along the floor of the sea. Gravitational forces then propagate a tsunami. Again, a marine volcanic eruption can generate an impulsive force that displaces the water column and gives birth to a tsunami.

Above water landslides and objects in space are capable of disturbing the water when the falling debris, like meteorites, displace the water from its equilibrium position. As a tsunami leaves deep waters and propagates into the shallow waters, it transforms.

This is because as the depth of the water decreases, the speed of the tsunami reduces. But the change of total energy of the tsunami remains constant. With decrease in speed, height of the tsunami wave grows. Tsunami attacks can come in different forms depending upon the geometry of the seafloor warping that first caused the waves. Sometimes, the sea seems to at first draw a breath but then this withdrawal is followed by arrival of the crest of a tsunami wave.

Tsunamis have been known to occur suddenly without warning. The water level on the shore rises to many metres: Waves can be large and violent in one coastal area while another is not affected. Areas can be flooded inland to metres or more; when tsunami waves retreat, they carry things and people out to sea. Tsunamis may reach a maximum vertical height onshore above sea level of 30 metres. The size of the tsunami waves is determined by the quantum of deformation of the sea floor.

Greater the vertical displacement, greater will be the wave size. For tsunamis to occur, earthquakes must happen underneath or near the ocean. They must be large and create movements in the ocean floor. Subduction zones off Chile, Nicaragua, Mexico and Indonesia have created killer tsunamis. The Pacific among the oceans has witnessed most number of tsunamis over since One of the deadliest tsunamis occurred in Asia on December 26, It was triggered by the most powerful earthquake recorded in the past four decades—one whose magnitude was 8.

A tsunami with a magnitude 9. Tsunamis and earthquakes can cause changes in geography. The Andaman and Nicobar Islands may have moved by about 1. The warning of an oncoming tsunami cannot be obtained by merely detecting an earthquake in the seas; it involves a number of complex steps which have to be completed in a systematic and quick fashion. It was in , that the international warning system was started. Computer systems at the Pacific Tsunami Warning Centre PTWC in Hawaii monitor data from seismic stations in the USA and elsewhere warning is issued when an earthquake is shallow, located under the sea or close to it and has a magnitude that is more than a pre-determined threshold.

Each gauge has a very sensitive pressure recorder on the sea floor in which can detect the change in the height of the ocean it even if it is by just one cm. The data is transmitted acoustically to a surface buoy which then relays it over satellite to the warning centre.

There are seven DART gauges deployed at present and four more are being planned. PTWC has improved its performance rapidly as high-quality seismic data has been made available to it.

The time it needed to issue a warning has fallen from up to 90 minutes some six years ago to 25 minutes or even less today. The Indian Ocean is not prone to tsunamis. Only two have occurred in this ocean including one on December 26, India has been a leader in the initiative to develop a reliable tsunami warning system for the ocean.

It has decided to set up a sophisticated system for detecting deep sea movements and develop a network with the countries in the Indian Ocean region for sharing information on tsunamis. It will have pressure sensors to detect the water movement. The sensors will be linked to the satellite that will relay information to the earth station.

Some more sensors would be installed later and the data buoys would be linked to the system that would record changes in the water level. The Indian government plans to set up a network with Indonesia, Myanmar and Thailand which would calculate the magnitude and intensity of tsunamis from the data available to it. DART-type gauges will be installed by the government and it will join 26 countries in a network that warn each other about tsunamis.

A state-of-the-art National Tsunami Early Warning Centre, which has the capability to detect earthquakes of more than 6 magnitude in the Indian Ocean was inaugurated in in India. The system comprises a real-time network of seismic stations, bottom pressure recorders BPRs , and 30 tide gauges to detect tsunamigenic earthquakes and monitor tsunamis.

Many regions in India are highly vulnerable to natural and other disasters on account of geological conditions. Disaster management has therefore emerged as a high priority.

Going beyond the historical focus on relief and rehabilitation after the catastrophe, there is a need to look ahead and plan for disaster preparedness and mitigation. So, the development process needs to be sensitive towards disaster prevention, preparedness as well as mitigation to ensure that periodic shocks to development efforts are minimised. About 60 per cent of the landmass in India is susceptible to earthquakes and over 8 per cent is prone to floods.

Of the nearly 7, km long coastline, more than 5, km is prone to cyclones. Around 68 per cent area is also susceptible to drought. All this entails huge economic losses and causes developmental setbacks. The Tenth Five Year Plan recognised disaster management as a development issue for the first time. It was prepared in the backdrop of the Orissa super cyclone and the massive Gujarat earthquake Later the Tsunami in the Indian Ocean which devastated coastal communities in Kerala, Tamil Nadu, Andhra Pradesh, Puducherry and Andaman in became the tipping point for initiating a series of steps by the government.

India became one of the first countries to declare a national commitment to set up appropriate institutional mechanisms for more effective disaster management at the national, state and district levels.

The Plan devoted a separate article to disaster management and made a number of important prescriptions to mainstream disaster risk reduction into the process of development.

The prescriptions were broadly divided into three categories:. Policy guidelines at macro level to inform and guide the preparation and implementation of development plans-across sectors. Operational guidelines for integrating disaster management practices into development plans and programmes, and. The significant initiatives on disaster management taken during the Plan period included the following:.

The Disaster Management Act, was enacted for establishing requisite institutional mechanisms for drawing up and monitoring the implementation of disaster management plans, and for undertaking a holistic, coordinated, and prompt response to any disaster situation.

Setting up of the National Disaster Management Authority NDMA as an apex body responsible for laying down of policies, plans and guidelines on disaster management so as to ensure timely and effective response to disasters. The guidelines on management of earthquake, chemical disasters, and chemical industrial disasters were finalised during the Plan period.

The other states and UTs are in the process of constituting the same. An eight battalion-strong National Disaster Response Force NDRF was set up comprising specialised response teams on various types of disasters of which around 72 are for nuclear, biological, and chemical NBC disasters. Revamping of the civil defence set-up to strengthen local efforts for disaster preparedness and effective response. Fire services also strengthened and modernised to a multi-hazard response force.

Inclusion of disaster management in the curriculum of middle and secondary school education. The subject has also been included in the post-induction and in-service training of civil and police officers. Modules have also been identified to include disaster management aspects in the course curriculum for engineering, architecture, and medical degrees. The other flood-prone areas are the north-west region with the rivers Narmada and Tapti, Central India and the Deccan region with rivers like the Mahanadi, Krishna and Kauveri.

The floods in Bihar in were one of the worst the country has seen. Floods in urban areas are rare. Streets do fill up with water, but drainage systems are usually in place to take care of excessive water logging.

The rapid and constant development of the city and the flouting of rules and regulations caused blockage and choking of the Mithi river that flows through a part of the city and used to carry off excess water to the sea. Violations of coastal regulation zone rules, development on green and no- development zones, building on areas marked for parks and open spaces all of this ensured that what little open space the city now had was not enough to absorb heavy rain.

An ancient and badly maintained drainage system added to the problem. In , more than eight states suffered the impact of severe drought. The states most exposed to cyclone-related hazards, including strong winds, floods and storm surges, are West Bengal, Orissa, Andhra Pradesh and Tamil Nadu along the Bay of Bengal. The impact of these cyclones is confined to the coastal districts, the maximum destruction being within km from the centre of the cyclone and on either side of the storm track.

The worst devastation takes place when and where the peak surge occurs at the time of the high tide. The population density in some of the coastal districts is as high as persons per square km. Cyclones have a devastating effect on the economy and lives of the people in the affected districts.

A very large population in the affected districts loose its source of livelihood. Public infrastructure suffers extensive damage. The economy of the state suffers a serious setback. This has an adverse impact on the development of the state. Some of the most devastating earthquakes in India in the past include the Kashmir earthquake in , the Kutch earthquakes and , the Shillong earthquake of , the Kangra earthquake of , the Bihar-Nepal earthquake of , the North-East and Assam earthquake of , the Anjar earthquake in Gujarat of, etc.

What made the earthquake more tragic was that many parts of the state were reeling under a drought for the second successive year.

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Natural disasters happen all over the world, and they can be utterly devastating for people’s lives and the environments in which they live. Although natural disasters are caused by nature and there is nothing that we can do to prevent them happening, there are many different natural causes that lead to natural disasters, and being aware of .

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- Natural Disasters can occur anywhere at anytime. Some are more predictable than others, but they all bring hardship to everyone’s life. Examples of natural disasters are Earthquakes (Haiti ), Tornadoes, Tsunami, Hurricanes, Wild Fires, Winter Storms, Heat waves, Mudslides and Floods. The responses to natural disasters have been to invest in early warning systems that tend to protect lives and properties (FEMA, Disasters ). People should manage natural disasters by bringing new emphasis to research, preparedness, response, and recovery. Agencies and systems have researched natural disasters for years.

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Natural Hazards and Natural Disasters A natural hazard is a threat of a naturally occurring event will have a negative effect on humans. This negative effect is what we call a . Essay on The Effect of Natural Disaster on a Society Words 5 Pages Even though it is currently possible to predict most natural disasters and minimize their consequences, major social impacts still have been seen over recent decades.