Understanding and Mitigating Risks: Natural and Human-Induced Hazards

1. Concept of Risk: Classification of Risks

Risk refers to any condition, process, or event that could cause injury, disease, economic loss, or environmental damage. This excludes wars and natural disasters, which are reaching greater magnitudes, especially hurricanes, floods, and earthquakes. Broadly speaking, we can classify risks into three groups:

a) Technological and Cultural Risks

These occur as a result of human error (e.g., oil spills) or dangerous lifestyles (e.g., assaults, drugs, alcoholism).

b) Natural Hazards

These are due to natural causes and may include:

  • Biological: Diseases caused by microorganisms such as parasites (bacteria, viruses), pollen, or animals like wasps or poisonous snakes (e.g., the Black Death, AIDS, locust plagues).
  • Chemical: Resulting from hazardous chemicals in food, air, water, or soil.
  • Physical: This includes risks such as ionizing radiation, noise, fire, and the following:
    • Climate/Weather: Tornadoes, hurricanes.
    • Geological: Due to internal and external geological processes, involving the hydrosphere and geosphere.
    • Cosmic: Originating from space, such as meteorite impacts.

c) Mixed Risks

These result from the induction or enhancement of natural hazards caused by human action.

2. Risk Factors

Vulnerability

Vulnerability (V) represents the percentage (or proportion) of total exposure to casualties or loss of tangible property caused by a specific event. Measures exist to reduce this factor, such as design techniques or the use of appropriate materials.

Danger

Danger is the probability of a phenomenon occurring whose intensity or severity makes it potentially harmful in a given time and space. First, its geographical distribution must be studied, as it often increases the extent of damage. Second, the recurrence interval must be known. Finally, its extent or degree of danger must be determined in degrees of intensity variables from the historical record.

Exposure

Exposure is the total number of persons or property subject to the risk. It can be reduced through the design of emergency strategies, such as civil protection and the installation of surveillance, control, and alert systems.

3. Prevention and Prediction of Volcanic and Seismic Hazards

The plan aims to develop measures to address all hazards.

Prediction

Prediction (forecasting is to announce in advance) has three components: spatial (where it will happen), temporal (when it will happen), and intensity.

Prevention

Prevention (to prepare in advance) involves applying measures to mitigate damage or eliminate the effects caused by different types of risks. These can be:

  • Structural: Changes in structures or the type of geological buildings suitable to prevent damage (reducing vulnerability).
  • Non-structural: Such as risk mapping to facilitate land use planning designed to find appropriate solutions for the location of future buildings.

Therefore, it is necessary to conduct risk maps, cartographic representations aimed at identifying risk areas for the following purposes:

  • Establishment of preventive measures, such as civil protection.
  • Establishment of corrective measures to avoid, as much as possible, disasters caused by them.

For the preparation of these maps, the following factors can be considered:

  • Hazard Maps: Widespread, often confused with risk.
  • Exposure Maps: Useful, as overcrowding increases risk.
  • Vulnerability Maps: Reflect social or economic losses, previously studied by geological cost index.
  • Risk Maps: Constructed using models developed from the previous three.

Each year, there are about 30,000 earthquakes worldwide, of which only about 75 are perceived by the population. The causes of earthquakes are varied: tectonic, volcanic eruptions, meteorite impacts.

Prediction of Earthquakes

The prediction of earthquakes in the short term is an unsolved problem, as it is currently impossible to announce the exact time they will occur.

Risks Arising from Earthquakes

The effects of an earthquake involve a number of risks, including:

  • Damage to buildings by cracking or collapse.
  • Instability of slopes, causing landslides, avalanches, or mudslides.
  • Rupture of dams and gas or water pipelines, with the consequent risk of flooding or fire.
  • Liquefaction, which is the effect on certain unconsolidated sediments like loose sand and silt, becoming fluid depending on their nature, interstitial water content, or the intensity or duration of seismic waves.
  • Tsunamis (tidal waves caused by a seismic event) and seiches (waves induced in inland waters).
  • Disappearance of groundwater and diversion of river channels.
  • Submarine landslides and collapse of sediments across the slope or dragging of deltaic deposits, causing turbidity currents.

Prevention of Damage Caused by Earthquakes

To prevent seismic effects, a series of measures are implemented, including seismic-resistant construction standards.