Natural Disasters - Tsunami: Causes, Effects and response

Natural disasters have inflicted a terrible toll on vulnerable communities around the world. The past few decades have seen an alarming increase in the occurrence of natural disasters and the magnitude of their impact on social, economic and environmental aspects.

The recurring floods in Assam and Bihar, frequent drought in Rajasthan and Gujarat coupled with the 2001 earthquake in Gujarat have disrupted the normal life of people across the country.

Disasters are as old as human history. Natural hazards such as cyclones; floods,

droughts and earthquakes have been analyzed technically and scientifically within scientific disciplines. Disasters can no longer be seen as ‘acts of God’ or ‘acts of nature’ over which we have little control nor can we leave disasters to be understood by natural scientists. We should behave as responsible future citizens of our country think of it and get ourselves prepared for a safer tomorrow.

The term ‘Tsunami’ has been coined from the Japanese term Tsu meaning ‘harbour’ and nami meaning ‘waves’. Tsunamis are waves generated by earthquakes, volcanic eruptions, or underwater landslides and can reach 15m or more in height devastating coastal communities. Tsunamis caused by nearby earthquakes may reach the coast within minutes. When the waves enter shallow water, they may rise to several feet or, in rare cases, tens of feet, striking the coast with devastating force. The Tsunami danger period can continue for many hours after a major earthquake.

Tsunamis are nearly always created by movement of the sea floor associated with earthquakes which occur beneath the sea floor or near the ocean. Tsunamis may also be generated by very large earthquakes far away in other areas of the Ocean. Waves caused by these travel at hundreds of kilometers per hour, reaching the coast several hours after the earthquake. Unlike ordinary tides, which are short, frequent and surface level, tsunami, are barely noticeable in their deep-sea formation stage. At this point despite a wavelength up to 100 km, they are shallow in depth and move at hundreds of

 Kilometer per hour.

Tsunamis can be very large. In coastal areas their height can be as great as 10m or more (30m in extreme cases), and they can move inland several hundred meters.All low-lying coastal areas can be struck by tsunamis.

A tsunami consists of a series of waves. Often the first wave may not be the largest. The danger from subsequent tsunami waves can last for several hours after the arrival of the first wave.

Sometimes a tsunami causes the water near the shore to recede, exposing the ocean floor. This is nature’s Tsunami warning.

The force of some tsunamis is enormous. Large rocks weighing several tons along with boats and other debris can be moved inland several meters by tsunami wave activity. Homes and other buildings are destroyed. All floating material and water move with great force and causing mortality or injuries to people.

Tsunamis can occur at any time of day or night.

Tsunamis can travel up rivers and streams that lead to the ocean thereby polluting them.

Tsunamis may also be generated by very large earthquakes far away in other areas of the Ocean. Waves caused by these travel at hundreds of kilometers per hour, reaching the coast several hours after the earthquake. Unlike ordinary tides, which are short, frequent and surface level, tsunami, are barely noticeable in their deep-sea formation stage. At this point despite a wavelength up to 100 km, they are shallow in depth and move at hundreds of kilometer per hour.

Detecting Tsunamis

1. With the use of satellite technology it is possible to provide nearly immediate warning of potentially tsunami-genic earthquakes. Warning time depends upon the distance of the epicenter from the coast line. The warning includes predicted times at selected coastal communities where the tsunami could travel in a few hours.
2. Coastal tidal gauges can warn of tsunamis close to the shore, but they are useless in deep oceans.
3. Tsunami detectors, linked to land by submarine cables, are deployed at a distance greater than 50 kms out at sea.
4. ‘Tsunameters’ transmit warnings of buoys on the sea surface, which relay it to satellites.

What to do BEFORE a Tsunami

1. Find out if your frequently visited locations are in tsunami hazard prone areas.
2. Know the height of your street above sea level and the distance of your street from the coast or other high-risk waters.
3. Plan evacuation routes from your home, school, workplace or any other place you could be where tsunamis present a risk.
4. Practice your evacuation routes
5. Have disaster supplies on hand.
6. Discuss tsunamis with your family
7. Develop an emergency communication plan. In case family members are separated from one another during a tsunami have a plan for getting back together.
8. Ask an out-of-state relative or friend to serve as the family contact (After a disaster, it is often easier to call long distance).

If you are at risk from tsunamis, you should:

1. Avoid building or living in buildings within several hundred feet of the coastline.
2. Make a list of items to bring inside in the event of a tsunami.
3. Elevate coastal homes. Most tsunami waves are less than 10 feet (3 meters). Elevating your house will help reduce damage to your property from most tsunamis.
4. Take precautions to prevent flooding.

1. Have an engineer check your home and advise about ways to make it more resistant to tsunami water.
2. Use a local radio or television station for updated emergency information.
3. Follow instructions issued by local authorities.

What to do DURING a Tsunami

1. If you are at home and hear there is a tsunami warning, you should make sure your entire family is aware of the warning. Your family should evacuate the house if you live in a tsunami prone area. Evacuate to a safe elevated area and move in an orderly, calm and safe manner to the evacuation site.
2. Take your Disaster Supplies Kit.
3. If you evacuate, take your animals with you.
4. If you are at the beach or near the ocean and you feel the earth shake, move immediately to higher ground.
5. Stay away from rivers and streams that lead to the oceans.
6. High multi-storey, reinforced concrete buildings (like hotels etc.) are located in many low-lying coastal areas. The upper floors of these buildings can provide a safe place.
7. Offshore reefs and shallow areas may help break the forces of tsunami waves, but large and dangerous waves can still be a threat to coastal residents in these areas. Staying away from low-lying coastal areas is the safest advice when there is a tsunami warning.
8. Update yourself on emergency information or warning announced on radio and television from time to time.

If you are on a boat or ship

1. Since tsunami wave activity is imperceptible in the open ocean, do not return to port if you are at sea and a tsunami warning has been issued for your area. Tsunami can cause rapid changes in water level and unpredictable dangerous currents in harbors and ports.
2. If there is time to move your boat or ship from port to deep water (after you know a tsunami warning has been issued), you should weigh the following considerations:

Most large harbors and ports are under the control of a harbor/port authority. These authorities direct operations during periods of increased readiness. Keep in contact with the authorities should a forced movement of vessels is directed.

Smaller ports may not be under the control of a port authority. If you are aware there is a tsunami warning and you have time to move your vessel to deep water, then you may do so in an orderly manner. Owners of small boats may find it safest to leave their boat at the pier and physically move to higher grounds.

Damaging wave activity and unpredictable currents can affect harbors for a period of time following the initial tsunami impact on the coast. Contact the harbor authority before returning to port.

After a tsunami, you should:

1. Continue using a radio or television for updated emergency information. The tsunami may have damaged roads, bridges, or other places that may be unsafe.
2. Check yourself for injuries and get first aid if necessary before helping injured or trapped persons. If someone needs to be rescued, call professionals with the right equipment to help.
3. Help people who require special assistance-infants, elderly people, those without transportation, large families who may need additional help in an emergency situation, people with disabilities, and the people who care for them.
4. Avoid disaster areas.
5. Use the telephone only for emergency calls.
6. Stay out of a building if water remains around it. Tsunami water, like floodwater, can undermine foundations, causing buildings to sink, floors to crack, or walls to collapse.
7. When re-entering buildings or homes, be very careful.
8. Wear long pants, a long-sleeved shirt, and sturdy shoes. The most common injury following a disaster is cut feet.
9. Use battery-powered lanterns or flashlights when examining buildings. DO NOT USE CANDLES
10. Examine walls, floors, doors, staircases, and windows to make sure that the building is not in danger of collapsing.
11. Inspect foundations for cracks or other damage. Cracks and damage to a foundation can render a building uninhabitable.
12. Check for gas leaks. Look for fire hazards. Fire is the most frequent hazard following floods.
13. Look for electrical system damage. Electrical equipment should be checked and dried before being returned to service.
14. Check for damage to sewage and water lines. Use tap water only if local health officials advise it is safe.
15. Watch out for wild animals, especially poisonous snakes. Tsunami floodwater flushes snakes and animals out of their homes.
16. Open the windows and doors to help dry the building.
17. Shovel mud before it solidifies.

The Orissa super cyclone of 1999 offers several lessons in disaster management. It hit the landfall point near Paradip coast on October 29 with a wind velocity of 270 to 300 km per hour. That cyclone and the one that preceded it on October 17-18 together affected over 19 million people, including 3.5 million children.

Whenever and where ever disasters strike the first responder for search and rescue always begins at the local levels: individual and neighborhood. Disasters or emergencies disrupt normal life. People living in highly vulnerable pockets cope up with frequent disasters on the basis of their acumen, accumulated knowledge, accumulated skills and resources of the community. In a post disaster scenario Search and Rescue has always played a major role in disaster management.

Search and rescue is a technical activity rendered by an individual or a group of specially trained personnel, who rescue and attend to the casualties under adverse conditions, where life is at threat.

Search and rescue activities are undertaken in two manners:

1. Community as Local Rescuers: With adequate safety measures, rescue activities are taken up immediately by the community after any disaster.
2. Outside Community Resources: Circumstances where the situation is grave and the local rescuers do not have required skills and equipments then specialist assistance from outside the community is required.

The main Objectives of a Search and Rescue Team are to:

1. Rescue the survivors trapped under the debris, from the damaged buildings or from a cyclonic storm surge.
2. Provide First Aid services to the trapped survivors and to dispatch them for medical care.
3. Take immediate necessary actions, as for temporary support and protection to dangerous collapsed buildings to structures.
4. Hand-over, recover and dispose-off the bodies of the deceased.
5. Train, demonstrate and raise awareness on how to use the local materials for rescuing the community people.

Rescue is a team effort that needs coordination and planning amongst the members for an optimum response operation. After the assessment, the Rescue Team would be in a position to adequately plan the Rescue Operation based on the following specifications:

Manpower       The Rescuers can use the skilled manpower if available and also take the help of the local community if required.

Equipment       Ropes, ladders, bamboos or stick, stretchers, boats etc are essential to rescue the affected victims. Sometimes these rescue materials are not available to the rescue team at the site of emergency. Therefore the rescuers use locally available resources like barrels, tinned cans, tubes etc.

Method            There are various other methods, which would be useful for rescuing the victims. The adequate method of rescue is to be determined depending upon the nature of the casualty, the nature of the injuries and the position in which the casualty is found.

Infra red cameras help in locating people under the rubble by detecting the body heat of the victim.

Acoustic devices can detect faint noises from the rubble

Bio radars are equipments used for the location of marooned victims in flood-affected areas.

First Aid has the following main objectives:

(i) To preserve life

(ii) To prevent the victim's condition from worsening

(iii) To promote recovery

A First Aid Kit consists of the following:

● Cotton wool

● Adhesive tape

● Crepe bandage

● Sterile Dressing

● Triangular Bandage

● Thermometer

● Scissors

● Glove

● Soap

● Pain reliever

● Antacid

● ORS Packets

Fainting or losing consciousness

Fainting is a brief loss of consciousness and is the result of an interference with the function of the brain.

There are many causes of unconsciousness, the most common of which are: fainting, head injury, epilepsy, stroke, poisoning, diabetes and conditions associated with lack of oxygen. If you have seen a person fainting then:

Do’s

❑ Catch the person before he/she falls

❑ Pinch the person and see if she moves or opens her eyes

❑ Examine the injuries and causes of unconsciousness

❑ Tilt head back and keep arms at right angle to body

❑ Raise the legs 8 – 12 inches. This promotes blood flow to the brain.

❑ Loosen any tight clothing

❑ Keep the victim warm if it is cold outside

❑ Keep a record of the casualty’s condition

Don’ts

❑ Don’t give the patient anything to eat or drink

❑ Don’t allow the person who has just fainted to get up until the victim is fully conscious

❑ If the area is warm, don’t crowd around the victim

COMMUNICATIONS DURING DISASTERS

The most popular means of communication is the public wired telephone, which is known as Public Switched TelephoneNetwork (PSTN) line. This is the prime network connecting all Government and Private offices, police stations, fire stations, hospitals and majority of homes and business places by transmitting and receiving voice, fax and data.

At the time of major natural disasters such as earthquake, cyclone, flood and landslide, the regular telecommunication infrastructure of public wired and wireless (mobile) telephones get severely damaged and become nonfunctional.

This mainly happens because of the damaged cables and cellular transmission towers or disrupted power supply that operate the telephone exchanges and cellular transmission towers.

The wireless radio communication network of Police and Civil authorities also gets affected due to damaged transmission towers. During this emergency situation, the communication traffic goes beyond its capacity which leads to congestion of the network or in worst case, complete failure of network.

At the time of any major disaster or emergency situation, it is extremely necessary to have the communication links operational among Government authorities at various levels and the people and volunteers working in the disaster affected areas to help the affected population.

Communication is essential in order to ensure the rapid movement of the right resources to the right place at the right time. It may also happen that some severely affected areas get completely disconnected from other parts of the world.

NIC: National Informatics Centre (NIC) is a premiere Science & Technology organization of the Government of India in this field. It functions through a nationwide information and communication technology (ICT) network called NICNET.

Modes for Emergency Communication

RADIO COMMUNICATIONS

A radio wave is an electromagnetic wave propagated by an antenna. Radio waves have different frequencies, and by tuning a radio receiver to a specific frequency you can pick up a specific signal. Hand held wireless sets (walky talky) are considered to be more suitable for local communication in case of such emergencies.

Amateur (Ham) Radio

In the event of major disasters/emergencies, it has been experienced that Amateur Radios have worked successfully when no other communications worked. Amateur radio, also known as ‘Ham radio’, does not refer to special kind of radio but to a special set of rules which apply to certain frequencies as defined by the International Telecommunications Union (ITU) and regulated in India by Wireless Planning and Coordination Wing, Ministry of Communications. The laid down rules allow these frequencies to be used only for research, education and personal purpose only. Amateur Radio operation does not use the ground based infrastructure, and has limited power requirements which can be easily met by batteries and generators and thus work successfully in emergencies. Amateur volunteers provided commendable services during the Orissa super cyclone in 1999 and Gujarat earthquake in 2001.

Satellite communication

Satellite based Communication systems mean communication systems intended for users on the Earth but which have some equipment in space. Communications satellites are essentially radio relay stations in space and are sometimes referred to as COMSATs. SATCOMS stands for satellite communications in general and SATPHONE for a satellite phone terminal. The most important feature of a communications satellite is the transponder - a radio that receives a conversation at one frequency and then amplifies it and re-transmits it back to Earth on another frequency.

A satellite normally contains hundreds or thousands of transponders. Telephone transmissions are routinely received and re-broadcasted by these transponders of communication satellites.

Currently, telephone transmissions are routinely received and re-broadcasted by these transponders of communication satellites.

Present operational Indian space systems include Indian National Satellite

(INSAT) for telecommunication, television broadcasting, meteorology and disaster warning and Indian Remote Sensing Satellite (IRS) for resources monitoring and

management.

                                     

This mode of communication is most reliable as Communications satellites are in space and not at all vulnerable to any natural disasters on the earth thus global communications links can be established with very small, portable and easy to install satellite antennas.

Most widely used means of satellite communications in disaster management is ‘satellite phone’. For these phones the satellite works as a telephone exchange.

These phones provide very reliable voice and data communication and are very handy and can be transported to any location.

Government of India is equipping the Disaster/Emergency managers in multi-hazard prone Districts/States with portable Satellite phones so that proper communication among the administrations at local and State level can be maintained in-case the main communication lines fail.

Radio communications and satellite based communication system are highly reliable and widely used.

The most successful way to mitigate loss of life and property, is to construct buildings that are disaster resistant.

GROUND MOVEMENTS

The ground movements caused by earthquakes can have several types of damaging effects. Some of the major effects are:

1. Ground shaking, i.e. back-and-forth motion of the ground, caused by the passing vibratory waves through the ground.

2. Soil failures, such as liquefaction and landslides, caused by shaking;

3. Surface fault ruptures, such as cracks, vertical shifts, etc.

4. Tidal waves (tsunamis), i.e. large waves on the surface of bodies of water that can cause major damage to shoreline areas.

EFFECT ON BUILDINGS

As the vibrations and waves continue to move through the earth, buildings on the earth’s surface are set in motion. Each building responds differently, depending on its construction. When the waves strike, the earth begins to move backward and forward long the same line. The lower part of a building on the earth’s surface immediately moves with the earth. The upper portion, however, initially remains at rest; thus the building is stretched out of shape. Gradually the upper portion tries to catch up with the bottom, but as it does so, the earth moves in the other direction, causing a “whiplash” effect. The vibration can cause structural failure in the building itself, or to an adjacent building having different response characteristics.

Taller buildings also tend to shake longer than short buildings, which can make them relatively more susceptible to damage. The primary objective of earthquake resistant design is to prevent collapse during earthquakes thus minimizing the risk of death or injury to people in or around the buildings.

The features to be taken into consideration at the stage of architectural planning and structural design of buildings for improved performance during earthquakes are listed below:

Building configuration

1. The building should have a simple rectangular plan.
2. Long walls should be supported by Reinforced Concrete columns
3. Large buildings having plans with shapes like T, L, U and X should preferably be separated into rectangular blocks by providing gaps in between.

Foundation

Buildings which are structurally strong to withstand earthquakes sometimes fail due to inadequate foundation design. Tilting, cracking and failure of structure may result from soil liquefaction.

Soil liquefaction refers to transformation of soil from a solid state to a liquid state as a consequence of increased pressure.

Control on openings in walls

Door and window openings in walls should preferably be small and more centrally located. Too many or large openings will make the wall vulnerable to collapse during earthquakes. The location of openings should not be too close to the edge of the wall.

Reinforced concrete bands in masonry buildings

For integrating the walls of an enclosure to perform together like a rigid box reinforced concrete bands are provided which run continuously on all external and internal walls including fixed partition walls. One or more of the following bands may be necessary in a building. Plinth band, lintel band, roof band, and gable band are names used for the band depending on the level of the building where the band is provided.

Vertical reinforcement

Vertical reinforcement should be provided at corners and junction of walls. It shall be passing through the lintel bands and floor slabs or floor level bands in all storeys. Earthquake doesn’t kill people. It is the badly designed buildings that kill the people. So to prevent an earthquake hazard from becoming a disaster our buildings should be properly designed incorporating the earthquake resistant design features into it.

Landslides

Landslides are among the major natural disasters or calamities in the world. In hilly terrains of India, including Himalayan mountains landslides have been a major and widely spread natural disasters that strike life and property almost perennially and occupy a position of major concern. These landslides, year after year, bring about untold misery to human settlements apart from causing devastating damages to transportation and communication network. Landslides, debris fall, debris slide, debris flow, rock toppling etc. cause destruction of slope and ground surface, initiating the change of uncontrolled erosion in the mountain terrains.

FACTORS THAT CAUSE LANDSLIDES

Landslides occur because of the interplay of several factors.

Natural factors

★ Intensity of rainfall

★ Steep slopes

★ Stiffness of slopes

★ Highly weathered rock layers

★ Soil layers formed under gravity

★ Seismic activity

★ Poor drainage

Man made factors

★ Deforestation leading to soil erosion

★ Non-engineered excavation

★ Mining and quarrying

★ Non-engineered construction

★ Land use pattern

MOST VULNERABLE HOMES

Vulnerable houses are those which are situated on:

1. Existing landslides area.
2. Steep natural slopes.
3. Areas in or at the mouths of drainages (such as canyons).
4. Houses constructed near foothills.

PROTECTION MEASURES FROM DAMAGE TO BUILDINGS

Site Selection

Landslides generally happen where they have occurred in the past, and in identifiable hazard locations. Areas that are typically considered safe from landslides include areas that have not moved in the past; relatively flat areas away from sudden changes in slope; and areas at the top of or along ridges. Houses built at the toe of steep slopes are often vulnerable to slides and debris flows.

Signs and Warnings

A house located on a hill can detect possible slope failure by watching for these signs:

1. Doors or windows stick or jam for the first time.
2. New Cracks appear on plaster, tile, brick or foundations.
3. Outside walls, walks or stairs begin pulling away from the building.
4. Slowly developing, widening cracks appear on the ground or on paved areas such as streets or driveways.
5. Underground utility lines break.
6. Fences, retaining walls, utility poles or trees tilt or move.
7. Water or bulging ground appears at the base of a slope.

The potential for landslides and destructive erosion can be greatly reduced or prevented with proper development, sound construction techniques, seasonal inspections and regular maintenance of drainage facilities.