MEV 012: Unit 13 - Introduction to Natural Hazards

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 UNIT 13: INTRODUCTION TO NATURAL HAZARDS

13.1 Introduction

Natural hazards are extreme events that occur due to natural processes of the Earth and have the potential to cause significant damage to life, property, and the environment. These hazards can be sudden and violent, like earthquakes and tsunamis, or slow-moving, like droughts and desertification. The study of natural hazards helps in understanding their origins, impacts, and possible mitigation measures.

13.2 Objectives

After studying this unit, you should be able to:

  • Understand what constitutes a hazard and how it differs from a disaster
  • Classify natural hazards based on their origin
  • Analyze the effects and functions of natural hazards
  • Assess the social, economic, and environmental impacts of hazards
  • Explain the concepts of risk and vulnerability
  • Understand international strategies for disaster risk reduction

13.3 Hazards and Disaster

  • Hazard: A potentially damaging physical event or phenomenon that may cause injury, loss of life, property damage, social and economic disruption, or environmental degradation.
  • Disaster: When a hazard leads to a serious disruption that exceeds the ability of the affected community or society to cope using its own resources.

Example: An earthquake in an uninhabited area is a hazard; in a populated city, it becomes a disaster.

13.4 Dimensions of Hazard

Natural hazards can be understood in multiple dimensions:

  • Magnitude: Intensity or energy release (e.g., Richter scale for earthquakes)
  • Frequency: How often a hazard occurs
  • Duration: Length of time the event persists
  • Areal Extent: Spatial coverage of the hazard
  • Speed of Onset: Sudden (earthquake) or gradual (drought)
  • Predictability: Ability to forecast the event

13.5 Hazards Classification

Hazards are classified based on their origin:

Type

Examples

Geophysical

Earthquakes, volcanoes, landslides

Hydrological

Floods, flash floods

Meteorological

Cyclones, storms, heatwaves

Climatological

Drought, wildfire

Biological

Epidemics, locust infestations

Extraterrestrial

Meteorites, space weather

13.6 Types of Natural Hazards

  1. Earthquakes – Ground shaking due to tectonic activity
  2. Volcanic Eruptions – Release of magma, gases, and ash
  3. Tsunamis – Seismic sea waves caused by undersea earthquakes
  4. Floods – Overflow of water beyond normal limits
  5. Cyclones and Hurricanes – Intense storm systems with high wind and rainfall
  6. Droughts – Prolonged shortage of rainfall
  7. Landslides – Downhill movement of soil and rock
  8. Wildfires – Uncontrolled fires in forest or grassland
  9. Heatwaves & Coldwaves – Prolonged periods of extreme temperatures

13.7 Effects and Service Functions of Natural Hazards

13.7.1 Effects of Natural Hazards

  • Loss of human lives
  • Destruction of infrastructure (roads, bridges, homes)
  • Displacement of people
  • Spread of diseases
  • Environmental degradation

13.7.2 Natural Service Functions of Hazards

Despite their destructive nature, natural hazards can also play constructive roles:

  • Volcanic eruptions create fertile soil
  • Floods deposit nutrient-rich sediments on floodplains
  • Forest fires help in seed dispersal and ecological regeneration
  • Earthquakes lead to landform changes and mountain building

13.8 Impacts of Hazards

13.8.1 Social Impacts

  • Loss of lives and displacement
  • Psychological trauma
  • Breakdown of social infrastructure
  • Increase in crime or conflict in refugee camps

13.8.2 Economic Impacts

  • Destruction of productive assets (farms, factories)
  • High cost of relief and rehabilitation
  • Loss in GDP and economic slowdown
  • Disruption of trade and tourism

13.8.3 Environmental Impacts

  • Deforestation and habitat destruction
  • Water and soil contamination
  • Coastal erosion due to cyclones and tsunamis
  • Loss of biodiversity

13.9 Concept of Risk and Vulnerability

Risk = Hazard × Vulnerability

A hazard may be natural, but risk depends on the vulnerability of the population exposed to it.

13.9.1 Factors of Vulnerability

  • Physical: Fragile housing, unsafe location
  • Social: Poor, elderly, or marginalized groups
  • Economic: Poverty, lack of insurance
  • Environmental: Deforestation, poor land use planning
  • Institutional: Weak governance and preparedness

13.9.2 Impact Assessment

  • Identifies who and what is at risk
  • Uses tools like hazard mapping, GIS, and vulnerability indicators
  • Helps plan mitigation and emergency response

13.9.3 Human Intervention and Response to Hazards

  • Urbanization in floodplains increases flood risk
  • Deforestation makes landslides more frequent
  • Building codes and early warning systems reduce disaster impact
  • Disaster preparedness and education improve resilience

13.10 International Strategies

13.10.1 The Sendai Framework for Disaster Risk Reduction (2015–2030)

An international strategy adopted by the UN to:

  • Reduce disaster risk and losses in lives, livelihoods, and health
  • Promote risk-informed development
  • Emphasize resilience-building in infrastructure
  • Focus on prevention, preparedness, and early warning
  • Encourage local, national, and international cooperation

The framework replaced the Hyogo Framework for Action and focuses on "Building Back Better" in recovery and reconstruction.

13.11 Let Us Sum Up

Natural hazards are inevitable, but disasters are not. With proper risk assessment, planning, and resilience-building, the damage can be mitigated. The study of hazards is essential for developing effective disaster risk reduction (DRR) strategies. This includes understanding hazard types, vulnerability factors, socio-economic impacts, and international efforts like the Sendai Framework. A proactive approach involving science, governance, and community participation is vital for sustainable disaster management.

13.12 Keywords

·         Natural Hazard-A naturally occurring physical phenomenon that may cause damage

·         Disaster-A serious disruption from a hazard causing widespread loss

·         Vulnerability-Conditions that increase susceptibility to hazards

·         Risk-The probability of harmful consequences due to hazards

·         Geophysical Hazard-Earth-originated events (e.g., earthquakes, volcanoes)

·         Hydrological Hazard-Water-related (e.g., floods, flash floods)

·         Mitigation-Measures to reduce risk and impact of hazards

·         Sendai Framework-Global UN strategy for disaster risk reduction

·         Resilience-Capacity to recover from hazards quickly and effectively

·         Hazard Mapping-Identification of areas at risk using GIS and other tools

 

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