Natural Hazards and Risk Assessment
Natural Hazards and Risk
Natural hazard is defined as the probability, small or large, that the population of an area suffers damage or disaster resulting from a natural process. Risk is the probability of losing human lives, property, or productive capacity due to any natural phenomenon. Natural hazards are physical phenomena of geological, atmospheric, or hydrologic origin that occur slowly or quickly and affect a territory or area at national, regional, or global levels. Geohazards can be endogenous (internal, like earthquakes) or exogenous (external, like heavy rains). If a hazard takes place in a specific area without causing significant change, it is an event. However, if it occurs unexpectedly with great personal and material damage, it is a catastrophe.
Factors for Assessing Risks
The factors for assessing risks are:
- Danger
- Interference (greater or lesser degree of fitness between the natural process that works in a particular area and the social process, that is, the way that people interfere with the process)
- Damage (transformations produced)
- Social catastrophe (costs arising from the catastrophe)
For the assessment of risks, the characteristics of the affected area, the natural process, and the repercussions of this on the population must be taken into account.
Prediction, Anticipation, Prevention, and Mitigation
Prediction, anticipation, and prevention of natural catastrophes involve identifying processes and risk factors that could pose a danger to the population in a given area. Prediction is knowing and announcing the occurrence of a natural phenomenon, including the place and time it will happen. Anticipation delves deeper into risk study because it provides information about its catastrophic potential, probability of occurrence, and frequency. Prevention covers all measures taken based on prediction and forecasting. Mitigation involves a set of decisions and measures to reduce the effects of risk.
Earthquake Risk
Effects of Earthquake Risk:
- Shaking of the ground and buildings
- Ground surface displacements
- Landslides
- Tsunamis
Earthquake Risk Measures:
- Establish areas with restrictions on construction
- Restrict land use on landslide-prone areas
- Strengthen the structures of existing buildings and design new ones to withstand ground shaking
- Promote the acquisition of insurance for large economic losses
Erosion
Erosion is the detachment and removal of materials from one area due to external geological processes such as surface water, glaciers, wind, etc. It may constitute a risk for two reasons: loss of resources (vegetation, crops, etc.) and the impact of the displaced materials.
Factors and Measures for Erosion Prevention:
Factors:
- Steep slopes
- Scarce vegetation
- Terrain materials
Basic Steps for Prevention:
- Determine the most appropriate use of land based on erosion function
Gravity Processes
Gravity processes are those involving material movement on steep slopes due to natural causes or human activity. The danger of these movements is that the materials may bury, drag, or hit buildings, people, infrastructure, etc., as they move down the slope.
Risks Related to the Subsoil
Risks related to the subsoil are:
- Sinking of the ground (usually a slow process that does not cause casualties but can lead to significant economic loss, caused by various factors like earthquake tremors, mine subsidence, etc.)
- Risks due to expansive soils (sinking causes the movement of foundations in buildings)
- Risks associated with karst formations (occurs in calcareous soil with subsidence and low consistency)
Tropical Cyclones
Tropical cyclones are very violent storms caused by the warming of air masses in very hot areas near the Equator, giving rise to strong winds and heavy rains. They are classified as follows:
- Tropical depression: winds of 62 km/h
- Tropical storm: winds of 62 to 118 km/h
- Hurricane: winds over 118 km/h
Catastrophes
Catastrophes are events that result from the interaction of exceptional events (both natural and man-made) with a population vulnerable to them. They cause damage, loss of life, economic ruin to a country, and slow down development. Natural disasters are those produced by natural phenomena.
Purposes of Studying Catastrophes:
- Understand economic and environmental loss
- Analyze loss of life
- Assess the impact on a country’s development
Types of Catastrophes:
- Natural: caused by the action of nature
- Anthropogenic: occur as a result of human activity and development
Factors that Increase the Risks of Disasters:
- Uncontrolled population growth
- Conditions of underdevelopment
- Urbanization and inappropriate use of high-risk technologies
- Environmental degradation and climate change