Understanding Erosion, Natural Risks, and Landslides
Erosion and Geological Activity
Erosion is identified as one of the principal external geological activities on Earth. Generally, it is considered responsible for the leveling of landforms over time, causing spectacular modifications in the geographical landscape. Various external geological agents exist, leading to different types of erosion. Key examples include:
- Wind erosion
- Glacier erosion
- River erosion
- Marine erosion
Prevention of Structural Damage from Floods
Structural Measures include:
- Building dikes
- Diversion channels
- Dredging channels
- Reforestation and soil conservation measures
- Rolling dams
Non-structural Measures include:
- Spatial planning
- Civil protection plans
- Flood risk simulation models
Understanding Natural Risks
Risk is any condition, process, or event that can cause personal damage (injury, illness, or death), economic loss, or environmental damage. It is estimated by multiplying the hazard (the probability of an event) by the vulnerability (the probability of damage) and the total exposure of persons or property at risk.
Types of Risks:
Natural Risks:
- Physical: Climatic, Geological (internal and external), Cosmic
- Chemical: Hazardous products in food, air, water, soil
- Biological: Diseases, pests, pollens, animals
Technological Risks:
- Risks associated with machines, accidents, and other human failings, including nuclear incidents
Mixed Risks:
- Alteration of natural processes by human action
Volcano Prediction and Prevention
Prediction:
- Return period and type of eruption
- Volcanic tremors
- Topographical changes
- Electro-magnetic and gravity anomalies
- Gas emissions
- Changes detected by satellite
- Risk mapping
Note: Explosive volcanism is difficult to predict.
Prevention:
- Divert lava flows
- Water discharge tunnels in filled craters
- Restrict construction in high-risk areas
- Reduce the level of reservoirs
- Planning evacuations
- Build houses with sloping roofs
- Fireproof shelters against hot clouds
Earthquake Prediction and Prevention
Prediction:
- Return period
- Seismic risk maps (P and E)
- Localization of active faults (satellite and radar)
Prevention:
Structural Measures:
- Earthquake-resistant buildings
- Avoid cramming buildings
- Build on rocky terrain
- Make buildings symmetrical and rigid with diagonal buttresses and insulating foundations
- Use flexible materials like rubber
- For soft soils, build low and not extensive buildings
- Secure water and gas facilities
Non-structural Measures:
- Flexible planning
- Evacuation plans
- Risk education
- Insurance
Note: Geodynamic processes affecting the Earth’s surface give rise to ground motion of different characteristics, size, and speed. These measures may not be effective in poor soil conditions.
Landslides and Ground Motion
The most common ground motions are frequent landslides, generally encompassing gravitational processes that occur on hillsides. Another type, although less widespread, is subsidence, associated with certain types of materials and conditions.
Types of Landslides:
- Landslides (deslizamientos): Gravitational mass movements of soil and/or rocks that affect natural slopes.
- Erosive processes: Widespread, causing destruction in any climatic region, affecting all types of materials and morphology.
- Flows: Mass movements of soils where the material is broken up and behaves like a “fluid,” undergoing continuous deformation without defined fracture surfaces. Examples include clay flows (fast) and solifluction (slow).
- Falls: Sudden free falls of blocks or masses of rock separated by pre-existing discontinuities, common in steep mountain slopes, cliffs, and rock walls. (Free Fall, rolling and tipping)
- Creep: Very slow crawling movement that occurs in the upper layers of clay slopes, resulting from expansion, contraction, and subsidence.
- Sinkholes: Characterized by vertical component movements, generally differing between subsidence (sudden movements) and settlement (slow movements).
Prevention of Landslides
- Risk Maps
- Civil protection measures
- Changing slopes
- Drainage on the slopes (gutters, ditches, wells, galleries) to prevent flows and landslides
- Containment measures (walls, nets, anchors)
- Plant trees and shrubs on the slopes
- Making the surface unstable anchors
- Marking areas of landslides