Geological disasters

Geological disasters

Geological disasters are caused by the transition of rock mass from stable equilibrium to the unstable state. This transition is accompanied by release of large amounts of energy. The disasters of this type are classified as:

1. Earthquake
2. Landslides
3. Tsunami
4. Mining

Earthquake

Earthquakes are one of the most dangerous and instantaneously destructive natural hazards. It is not possible to forecast earthquakes with regard to time and place of occurrence or magnitude. A large portion of our country is vulnerable to earthquake activity of varying magnitudes. The nature and impact of earthquake disaster is dependent on:

• its magnitude
• geological and soil conditions
• location of fault
• construction of major structures and 
• prevailing construction practices in the particular areas.

India has a very long history of earthquakes. A few major earthquakes are listed below:

1. Rann of Kutch (1819) magnitude 8.0
2. Assam (1897) magnitude 8.7
3. Kangra (H.P.) (1905) magnitude 8.0
4. Bihar-Nepal border (1934) magnitude 8.4
5. Andaman Islands (1941) magnitude 8.0 and
6. Assam (1950) magnitude 8.6.

In the recent past, India experienced major earthquakes at 

1. Uttarkashi (1991)
2. Latur (1993) and Jabalpur (1997)
3. Chamoli (1999) 
4. Bhuj (2001).

In the earthquake that occurred at Uttarkashi:

• The affected area had a known history of earthquake occurrence and widespread damage took place due to this earthquake.
• The non-engineered buildings found throughout the rural areas and the old stone buildings in the towns suffered severe damage.
• The engineered buildings faced the earth quake in a very safe manner and suffered no damage, except for minor cracks in the buildings
• There was large scale damage to infrastructural facilities in the earthquake affected area.
• The damage to roads was due to rockfall, landslides and' rock-slides along the road side slopes causing heavy damage
• Services like communication network and power supply system were affected very badly
• The buildings that house health and education facilities suffered damaged the joints in the piped supply lines failed due to ground shaking, resulting in disruption of water supply
• A large number of bridges were located to cross the rivers and deep river valleys throughout the hilly area. 
• The Gawana bridge on the road to Gangotri suffered 'slight to medium damages.

In the earthquake that occurred at Latur:

This earthquake struck the Marathwada region of Maharashtra state on 30th September 1993. The impact of this earthquake was felt in the adjoining states of Andhra Pradesh and Karnataka

also.

• Widespread damage took place due to this earthquake.
• Due to the earthquake most of the houses were destroyed' causing death of people in large numbers as also a wide spread damage to installations and properties
• The entire region had a traditional system of dwelling unit construction which involved heavy stone walls, and a massive roof over the wooden timber sub-structure. 
• During the earthquake most of the houses were destroyed' causing death of people in large numbers along with widespread damage to installations and properties
• Army services were pressed into action for the rescue operation. This involved clearing rubble, rescuing the injured, removal and cremation of dead bodies.
• Provisions were made for temporary relief shelters to the survivors of the earthquake. These
• shelters were made up ofG.1. (galvanized iron) sheeted roofs over the bamboo
• or wooden frames. About 30,000 families were provided the temporary
• shelters in the two worst affected districts of Latur and Osmanabad,

Landslides

• Landslides are simply defined as the mass movement of rock, debris or earth down a slope and have come to include a broad range of motions whereby falling, sliding and flowing under the influence of gravity dislodges earth material. 
• They often take place in conjunction with earthquakes, floods and volcanoes. At times, prolonged rainfall causing heavy block the flow or river for quite some time. 
• The formation of river blocks can cause havoc to the settlements downstream on it's bursting. In the hilly terrain of India including the Himalayas, landslides have been a major and widely spread natural disaster the often strike life and property and occupy a position of major concern.

The two regions most vulnerable to landslides are 

• the Himalayas and 
• the Western Ghats. 

The Himalayas mountain belt comprise of tectonically unstable younger geological formations subjected to severe seismic activity. The Western Ghats and Nilgiris are geologically stable but have uplifted plateau margins influenced by neo- tectonic activity. Compared to Western Ghats region, the slides in the Himalayas region are huge and massive and in most cases the overburden along with the underlying lithology is displaced during sliding particularly due to the seismic factor.

Incidences of landslides in India

Himalayas                                                                       - High to very high

North-eastern Hills                                                         - High

Western Ghats and the Nilgiris                                       - Moderate to high

Vindhayachal                                                                  - Low

Tsunami

• 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 kilometres per hour, reaching the coast several hours after the earthquake.
• 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 kilometres 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 kilometre per hour.

Mining

Disaster Management

 Disaster Management

Disaster management is a process of effectively preparing for and responding to disasters. It involves 

• strategically organizing resources to lessen the caused by disasters. 
• a systematic approach to managing the responsibilities of disaster prevention, preparedness, response, and recovery.

Disaster management efforts aim to reduce or avoid the potential losses from hazards, assure prompt and appropriate assistance to the victims of a disaster, and achieve a rapid and effective recovery.

Disaster and Development

Disaster and Development

Historically it has been seen there has been an apparent increase in the number of natural disasters resulting in increasing losses due to urbanization and population growth. This is a rigid one-sided outlook of development that recognizes only growth aspect, without an eye on sustainability. In the context of definition of a disaster. we recognize only damage and destruction. 

With reference to the tsunami in 2004, Maldives, Sri Lanka, and Thailand suffered from non-ecologically sustainable over-development in coastal areas and India, Sumatra and North East Sri Lanka, suffered because affected pockets were inaccessible due to underdevelopment and impoverishment of the people. Such disastrous events have demonstrated that development has to continue, but with due concern for protection of the environment.

Science and technology should be fruitfully employed to control disasters. Alternatives should be generated by research and development in science and technology with emphasis on science and technology, especially information communication technology (ICT) for better understanding of disasters and better reach of disaster response efforts

Disasters and Development are interrelated, both in positive and negative ways. 

With regard to the relationship between disasters and development we can identify ‘four’

different dimensions to this relation:

1. Disasters can set back development by wiping out decades of economic and social development. Disasters can also limit social development. Disasters worsen poverty in communities.
2. Disasters can provide development opportunities by development policy in the aftermath period. Disasters can elevate the development potential of a society by becoming a catalyst for change in the form of reconstruction and social development as well as upgrading administrative capability and training of personnel involved. Ex: Reforestation programs after landslides and flash floods to check soil erosion, have spin off effects on other sectors, such as improved air quality, better flora and fauna, health and longevity for people, etc. These in-turn work as development programs in the form of more sources of income for the poor, enhanced employment opportunities, etc. Development opportunities often are compromised because of excessive focus on relief assistance. Disasters can also be a major vehicle for carrying out major development programs.
3. Development can increase vulnerability as Social and economic development can increase the vulnerability of the community to disaster risks. It has been shown time and again that economic development increases disaster risk. Rapid urbanisation has increased the vulnerability of the community. Urban development often leads to an influx of relatively low income groups, with large scale settlement of marginal land or in high density, poor quality housing. Marine and coastal zone development leads to population concentrations, exposed to possible storm surge, high wind, flash flood and landslide risks. 
4. Development can reduce vulnerability as demonstrated in the examples given below:
1. Disaster resistant technologies in buildings that are being newly constructed in Malaysia is a good example of development oriented towards risk reduction
2. Social development includes awareness/education to reduce human vulnerability and limit losses in a disaster
3. A literate and better-educated population, including women and girls, is better able to cope up effectively to any disaster by responding effectively to early warnings

Capacity

 Capacity

The International Strategy on Disaster Reduction (ISDR), United Nations (UN), defines Capacity “as a combination of all the strengths and resources available within a community, society or organization that can reduce the level of risk, or the effects of a disaster. This involves managing resources, both in normal times as well as during crisis or adverse conditions. The strengthening of coping capacities usually builds resilience to withstand the effects of natural and induced hazards.”

It is widely believed that vulnerability and capacity should be integrated in all assessments with regard to disaster management. The severity of the impact of a disaster depends on the balance of vulnerability and capacity of a particular community.

As per the FAO directory, "Within the context of disaster management, development is defined as a process that reduces vulnerabilities and increases capacities".

The five categories involving Vulnerability and Capacity Analysis (VCA) are:

1. Economic 
2. Natural
3. Physical
4. Human, and 
5. Social

Risk

Risk

“Risk” usually refers to the probability of loss of a ‘valued resource’. In the context of health and environmental risks, the word “risk”  integrates two ideas:

1. the potential for detrimental consequences and
2. the uncertainty associated with the circumstances

In the context of disaster management, risk implies application of knowledge to forewarn of disasters accurately and anticipate the risks involved with regard to land use management and project planning decisions in hazard prone areas so as to prevent/reduce impact. 

With regard to disaster terminology, Risk is defined as “the likelihood of a specified undesired event occurring within a specified period or in specified circumstances.

Risk = f (frequency or probability, consequence)

Frequency is usually expressed as events per year 

Probability is a number between 0 and 1

Consequence is usually measured in terms of either money or fatalities

Hazard is a potentially dangerous situation

Disaster is a hazard leading to a catastrophe

Vulnerability is the physical, social, economic, cultural or based on inclination to hazards

Risk is the harm likely from anticipated event and may be measured through comparative analysis of data collected over time and scientific simulation studies. Measurement of risk in disaster management is a complex issue.

Hazard

Hazard

According to the United Nations International Strategy for Disaster Reduction (UNISDR), a hazard is a natural process or phenomenon that may pose negative impacts on the economy, society, and ecology. It includes both natural factors and associated human factors.

A hazard can be defined as a potentially damaging physical event, social and economic disruption or environmental degradation. Hazards can be the creation of man or the environment. 

A hazard is always present and it simply acts as a catalyst to bring adverse effects into focus. A hazard is defined as a potential cause which is activated when the right configuration of factors present themselves. A hazard may or may not lead to an event. 

A hazard is defines as “a potentially damaging physical event, phenomenon or human activity that may cause the loss of life or injury, property damage, social and economic disruption or environmental degradation.” Hazards could be, natural (geological, hydro-meteorological and biological) or induced by human processes (environmental degradation and technological hazards).

Hazards can be single, sequential or combined in their origin and effects. Hence, Hazard analysis entails the identification, study and monitoring of a hazard to determine its potential, origin and characteristics. 

Hazards are generally classified as:

• Sudden onset hazards: geological and climatic hazards such as earthquakes, tsunamis, floods, tropical storms, volcanic eruptions, and landslides.
• Slow onset hazards: (environmental hazards) drought, famine, environmental degradation, desertification, deforestation, and pest infestation.
• Industrial/Technological: system failures/accidents, spillages, explosions, and fires.
• Wars and civil strife: armed aggression, insurgency, terrorism, and other actions leading to  displaced persons and refugees.
• Epidemics: water and/or food-born diseases, person-to-person diseases (contact and respiratory spread), vector-born diseases and complications from wounds.

Hazards could also be classified as direct and indirect. 

Examples of "Direct Hazards" include:

• Ground shaking
• Differential ground settlement
• Soil liquefaction
• Immediate landslides or mud slides, ground lurching and avalanches
• Permanent ground displacement along faults
• Floods from tidal waves, sea surges & tsunamis

Examples of "Indirect hazards" include:

• Dam failures
• Pollution from damage to industrial plants
• Delayed landslides.

Site risks in an earthquake prone area include:

• Slope risks
• Natural dams (formed by landslides in irregular topographic areas and are susceptible to collapse when filled leading to catastrophic avalanches after strong seismic shaking)
• Volcanic activity

Hazards can also be classified as long-term of short-term as per the classification proposed by K. Smith

Identification of hazards involves analyses of scientific data to trace the causal path of

events leading to a disaster.