24 NATURAL HAZARDS AND DISASTERS

Sushmitha Baskar

Structure

 

1.0 Objectives

 

1.1 Introduction

 

1.2 Definitions: Hazard and disaster

 

1.3 Dimensions of disaster

 

1.4 Classification of natural hazards

 

1.5 Effects of hazards

 

1.6 Natural service functions of natural hazards

 

1.7 Vulnerability

 

1.8 Natural hazards and human intervention

 

1.9 Hazard assessment

 

1.10 National and International attention: Hazard Mitigation

 

1.11 Summary

 

1.12 Key Words

 

1.13 References and Suggested Further Readings

 

1.0 OBJECTIVE

 

  • After reading this unit, you should be able to:
  • define the term natural hazards and disaster;
  • explain the types of natural hazards and their effects; and list the measures for hazard mitigation.

1.1 INTRODUCTION

 

Hazards originate from the interplay of physical, biological and social systems. India is prone to natural disasters such as earthquakes, floods, cyclones and droughts. Environmental degradation is accelerating the vulnerability to natural disasters. Some major natural hazards that India as  experienced include: the Kashmir floods in 2014, the Uttarakhand flash floods in 2013, the Indian Ocean Tsunami in 2004, the Bhuj earthquake in Gujarat in 2001, the Odisha Super cyclone in 1999 and the earthquake in Latur, Maharashtra in 1993. These hazards are considered most hazardous and have lead to serious economic loss and loss of lives.

 

Our planet earth is an ever dynamic, evolving system with complex interactions of internal and external processes. The movement of plates, earthquakes, volcanic activities is due to the internal processes. Floods, hurricanes, tornadoes and droughts are caused as a result of external processes. The source of energy for the internal process is radioactivity, and the source of energy for the external process is the sun. Natural hazards can be extreme event can lead to several other disasters which can be hazardous. For example, earthquakes result in landslides and in the destruction of buildings. This in turn can contaminate water sources resulting in water borne diseases i.e. cholera outbreak after the 2010 Haiti earthquake.

 

1.2 DEFINITIONS: HAZARD AND DISASTER

 

Earth processes are natural events that occur within the lithosphere, hydrosphere or atmosphere. They become hazardous only when they affect life or property. These life or property threatening processes is called natural hazards. For example the earthquake that occurred in Kobe, Japan in 1995 witnessed 5000 deaths and 200 billion dollars loss. This was a deadly earthquake and costly in a developed country. Human activities play an important role in how severe a hazard can be.

 

 

Hazard: A hazard can be defined as: “The elements of the physical environment, harmful to man and are caused by forces extraneous to him” (Burton et al. 1978). A hazard has the potential to cause harm to: people, human activity, property and the environment. Disaster: A disaster is the realization of the hazard.

Hazard Event: They are physical parameters of the hazards which cause harm to humans and society. Environmental events can become hazards when they cause adverse effects to the society and the environment. Volcanic eruptions mostly do not cause harm to humans. Hence it is termed a natural phenomenon. Such natural phenomenon events that occur in a populated region are referred to as hazardous events.

 

Natural disaster: A Hazard event that causes a very large number of fatalities and damage to property is known as a natural disaster. In order to understand natural hazards and to predict and prepare ourselves for the same let us now learn in detail about the dimensions of a hazard and hazard classification.

1.3 DIMENSIONS OF HAZARD

In order to understand the impact of a hazard; the magnitude, the frequency and the intensity at the impact point is of importance. Further, some other factors like climate, geology, vegetation, population and land use is equally important. Most hazards have return periods on a human time-scale. For example, there are five-year floods, fifty-year floods etc. This gives an estimate of how often the hazard event of a given magnitude and intensity will reoccur.

 

1.4 CLASSIFICATION OF NATURAL HAZARDS

 

Natural hazards can be classified as: geological, hydrological, meteorological and biological hazards.

 

 

1.4.1 Natural Hazards

 

(a) Geological

 

Geological hazards are caused due to earth processes. Earthquakes, volcanic eruptions, landslides, avalanches, subsidence, and impacts with space objects are some examples of geological hazards. Among all these, earthquakes release maximum energy in a short duration. Earthquakes cause large scale loss of life and property and disrupt most essential services such as water supply, communication, power and transport.

(b) Hydrological

The natural hazards that are triggered exclusively by hydrological extreme-event phenomena of nature are called “hydrological hazards” or simply “water hazard. They include floods, droughts, mudslides and tsunamis. Among these floods are the most frequent and cause damage to life and property.

 

(c) Meteorological

 

Meteorological hazards are those hazards caused due to weather/ metereological processes. They include: cyclones, hurricanes, tornadoes, droughts, lightening thunderstorms, heavy rain and flooding, heatwaves and bushfires. A number of other hazards such as hail, flooding or wind can also occur as a result of more than one of these meteorological phenomena.

The above hazards are primary hazards. Natural Hazards can also be termed as catastrophic hazards when they have devastating consequences to large numbers of people.

 

 

(d) Biological Hazards

 

Biological hazards are caused by biological agents. They include disease infestations such as the outbreak of bubonic plague in the 1300s which killed 100 million people, and the 1918 “Spanish” flu pandemic. Epidemic is defined as the occurrence of an illness or other health catastrophes which affect large number of people. Epidemic outbreaks of communicable diseases are potentially high after a disaster. It may be due to poor environmental conditions leading to water contamination and subsequent breeding of the disease vectors. Epidemics cause mass illness and/or death. Epidemics may be the consequence of primary disasters such as cyclones, floods, earthquakes etc. Epidemics can also affect animals leading to economic disasters.

The vulnerability is high among those who are poorly nourished, people living in unhygienic in sanitary conditions, poor quality of water supply, lack of access to health services. Some examples of biological hazards include Dengue, Avian flu, Swine flu, Cholera, Chikungunya and Bubonic plague.

 

1.4.2 Secondary hazards: They occur as a result of other primary hazards. For example a primary hazard is the earthquake. Dam failures, building collapse, ruptured power and water lines, landslides, tsunami etc. are some types of secondary hazards that can result due to an earthquake.

1.4.3 Chronic hazards: These are referred to as chronic because they are a group of hazards that do not originate from one event. They occur due to continuous hazardous conditions such as pollution, toxic contamination that accumulate over time and so on.

 

 

Natural hazards can also further be classified into rapid onset hazards and slow onset hazards. Examples of rapid onset hazards include volcanic eruptions, earthquakes, floods, landslides, severe thunderstorms that strike rapidly. Examples of slow onset hazards include drought and disease epidemics that are slow and take years to form. Therefore the speed of onset of a hazard is an important factor. Spatial dispersion is the distribution pattern of a hazard over the geographic area where hazard can occur. Temporal spacing refers to the sequencing and seasonality of events. Hazard scape refers to the landscape of numerous hazards. These hazards affect people and the places they live in with the interaction on nature, society, and technology at a variety of spatial scales. This term is generally used in reference to a specific region. Every hazard has a different space and time characteristic (Table. 1.1; Navalgund, R.R. 2001).

 

 

India has been affected by many natural hazards which resulted in the loss of many lives and property.The decade (1990-99) was the International Decade for Natural Disaster Reduction (1990-99).

 

 

1.4.4 Man-made hazards

 

These hazards are also referred to as technological hazards. They include: exposure to hazardous substances, such as radon, mercury, asbestos fibres, acid rain or contaminated waters. They also include chemical disasters and fires.

 

 

(a) Chemical Disasters

 

Industrial disasters are an example of man-made disasters. There was an increase in the growth of the chemical industry after the Second World War. This led to a number of chemical disasters. In these disasters there are uncontrolled events involving fires, explosions or releases of toxic substances that result in the death/ injury of people and extensive environmental and economic damage. In India, the Bhopal gas tragedy that occurred in Bhopal, 1984 was a major worst chemical disaster.

(b) Slow-Onset Disasters

This type occurs when humans are exposed to environmental toxic substances released due to man-made pollution activities. An example is the “Minamata disease”. A factory discharged its effluent containing inorganic mercury into Minamata Bay, Japan. The bacteria converted this into organic methyl mercury which was consumed by the fishes in the bay. In 1953 it was observed that the fishes in the bay were lethargic and the humans who had consumed these fishes had unusual neurological disorders. The disease was named kibyo, the “mystery illness”. The victims complained with polyneuritis, cerebellar ataxia, cortical blindness which was due to mercury poisoning.

 

 

(c) Fires

 

Fires can cause environmental pollution and are a threat to human life, property and wild life. They can spread rapidly and cause extensive damage in a short time. Man-made causes of fires include: trashing burning matchsticks, during cooking from LPG gas or kerosene, short circuits in electrical wirings, forest fires and during transportation of inflammable material or explosive chemicals. These are some types of man-made disasters.

 

 

SAQ1

 

  1. Define hazard and disaster.
  2. How are hazards classified?

1.5 Effects of Hazards

 

Natural hazards cause a number of primary, secondary and tertiary effects. The severity of the secondary effects produced varies with the type of event. Tropical cyclones bring strong winds and heavy rains which cause secondary hazards such as flood, storm tide, landslides and water pollution. Flood inundates areas, which in turn may lead to landslide, erosion, water quality deterioration or turbidity, as well as sediment deposition. Earthquakes may also bring fire, flood, water pollution, landslide, tsunami and soil liquefaction, which can be as devastating as the primary hazard.

Primary effects: These occur due to the process itself. Examples include: building collapse as a result of an earthquake or a landslide.

Secondary effects: These occur since a primary event has caused them. Examples include: fires ignited due to volcanic eruptions; power and water service disruptions due to earthquakes.

 

Tertiary effects: These are long term effects which are normally set off due to primary events. Some examples include: crop failures caused due to volcanic eruptions and loss of habitats due to severe floods.

 

 

1.6 Natural Service functions of natural hazards

 

Natural hazards also have some important natural service functions for the biosphere and people. For example, volcanic activities have been responsible for producing the hydrosphere and the atmosphere. Soil is replenished as a result of floods and landslides. Further, in rivers water flows over the riverbanks and the floodplain. So water and nutrients are stored on the floodplain and the floodplain has nutrient rich soils. Therefore the physical processes linked to the biological environment produce varied landscapes. It is only because of the disturbances from natural processes, such as earthquakes, floods and so on there is water availability and the soils are fertile.

 

 

1.7 Vulnerability

 

Vulnerability refers to not only the possible physical effects of a natural hazard, but the way it can affect the human life and to property. Vulnerability to natural hazards depends on a number of factors. They include the following:

 

  • Ø Proximity to a possible hazardous event
  • Ø Population density, construction styles and building codes
  • Ø Understanding and awareness of the nature of the hazard
  • Ø Early-warning systems, lines of communication and emergency infrastructure

 

Generally, developing nations are more vulnerable to natural hazards than the developed ones. This is because of lack of understanding, education, infrastructure, and poor building codes.

1.8 Natural hazards and human intervention

Human beings can do nothing about the incidence or intensity of most natural phenomena. They can however help in changing their behavior and action to the environment, so that natural events do not turn into disasters. Human intervention can increase the frequency natural hazards. For example, when the toe of a landslide is removed for a settlement, there can be disasters. This is human-induced.

 

Volcanic eruptions occur periodically. But when the fertile soils formed on their surface are occupied by humans for farms, they can be hazardous. Therefore, human intervention in such natural processes can increases vulnerability by the following:

 

Development and habitation of lands susceptible to hazards Human interventions reduce the mitigating effect of natural ecosystems. The destruction of coral reefs, (which protects from storm surge and ocean currents) cause disturbances to the natural coastal ecosystem.

 

 

1.9 Assessing Hazards

 

Hazard Assessment is also known as Hazard Evaluation or Hazard Analysis (UNDRO, 1991). It is the process of estimating the probabilities of the occurrence of a disaster of a given magnitude within a specified period of time. The probability of a hazard occurrence differs from each place. The use of mapping to understand natural hazards data improves to network among people in the hazard management process and between planners and decision-makers. Hazard assessment process consists of answering the different hazardous processes that have occurred in the past, the magnitude and frequency of the past hazardous processes and the socio-economic impacts of a hazardous event. It also involves the analyses of locations, buildings and highways that are subject to hazards. The above information is collected and presented to the concerned public officials, scientists and decision makers for making decisions and mitigation steps in event of a disaster.

1.10 National and International Attention: Hazard Mitigation

The year 1990’s was designated as the International Decade for Natural Disaster Reduction (IDNDR) by the United Nations with primary goal to reduce the loss of life, property, socio-economic disruption caused by natural disasters. Within this context the IDNDR advised the UN-member states to establish National Platforms which would facilitate the adjustment of general disaster risk reduction objectives to national/local conditions implement the agreed policies and expand the understanding and perception of the importance of disaster risk reduction on national levels. The (international strategy for disaster reduction) ISDR aims to push the initiatives and cooperation agreed on during the IDNDR, and developing new mechanisms as well as ensuring for further commitments from policy-makers.

 

The ultimate goal is to reduce human, social, economic and environmental losses due to natural hazards.

 

The Yokohama conference, 1994 underlined the need for shift in the strategy for disaster mitigation. In this conference, it was stressed that disaster prevention, mitigation, preparedness and relief are fundamental to sustainable development policies. Hence all nations should incorporate disaster management in their development plans and ensure follow up measures at the national and international levels. The Yokohama conference also discussed that disaster prevention, mitigation and preparedness are essential to integrated disaster management. The Government of India has adopted mitigation and prevention as essential components of their development strategy. The Tenth Five Year Plan has a detailed chapter on Disaster Management. This plan emphasizes that development cannot be sustainable without mitigation institutionalized into developmental process.

Hazards are an integral part of life and no one can live in an environment totally free of hazards and disasters. Each hazard varies in dimensions and assessing hazards is the first important step for adopting the strategies. Policies play an important role in influencing the impact of natural disasters, in emergency management, land use planning and construction standards.

 

 

SAQ 2

 

  1. Explain the effects of hazards.
  2. Describe vulnerability and human intervention.

 

 

1.11 Summary

 

In this unit we have studied about natural hazards and disasters, their types, effects, impacts, vulnerability, human intervention and an overview of assessing hazards. By understanding the consequences of hazards and disasters we increase our awareness and help protect communities, infrastructure and our economy. Natural hazards will continue, but with scientific understanding and effective preparedness, the devastation can be reduced to a great extent. Further, past events are learning strategies and with innovative research and technology we can build more resilient and safer communities on our planet.

 

1.12 Key words

 

Hazard: It can be defined as a potential threat to humans and their welfare and risk as the probability of hazard occurrence. Disaster: It can be defined as the realization of the hazard.

 

 

1.13 References and Suggested further readings

 

 

  • Baskar, S and Baskar, R. 2009. Natural Disasters. Unicorn books, Pustak Mahal, India. 159p.
  • Bryant, E. 2005. Natural Hazards. 2nd Edition, Cambridge university press, 330p.
  • Burton, I. And Kates, R.W. (1964). The perception of natural hazards in resource management, Natural Resources Journal 3, 412-41.
  • Burton, I., Kates, R.W., and White, G.F. (1978) The Environment as Hazard New York: Oxford University Press.
  • Hewitt, K. and Burton, I. (1971). The Hazardousness of a Place: A Regional Ecology of Damage Events, University of Toronto.
  • Keller, E.A. 2010. Environmental Geology, 9th Edition, Pearson publication, 624 p.
  • United Nations Disaster Relief Organization.       (1991). Mitigating Natural Disasters:       Phenomena,
  • Effects and Options:  A Manual for Policy makers and Planners. New York: United Nations.