Understanding Geological Hazards and Risk Management
Erosion Risks and Impacts
Erosion is the starting and removal of materials from an area due to eroding agents involved in external geological processes, such as surface water, glaciers, wind, etc.
Erosion risk can constitute a threat for two main reasons:
Loss of Vital Resources
The most significant impact is the loss of soil, a vital resource for the development of vegetation, ecosystems, and crops, which can lead to desertification.
Impact of Mobilized Materials
When surface water starts and carries large amounts of sediment, these materials pose a significant risk. They can clog dams or block hydro turbines, increase sedimentation rates in littoral areas, and alter coastal dynamics and human activities.
Gravitational Process Risks
The movements of materials on sloping hillsides occur relatively frequently and may be due to natural causes or human activity in the field. This phenomenon can often be anticipated and effectively avoided. The hazardous nature of gravitational displacement stems from two main points:
Direct Impact and Burial
The possibility of moving materials hitting, devastating, or burying people, buildings, or crops.
Displacement of Structures
The fact that the ground on which people, infrastructure, etc., are settled moves down the slope.
Gravitational movements include rockfalls, landslides, mudslides, or mass flows.
Preventing Gravitational Hazards
Key actions to prevent risks due to gravitational processes include:
- Reducing the inclination of the slope.
- Eliminating excess weight at the head and foot of the slope.
- Strengthening and adding weight to the foot of the slope.
- Implementing effective drainage systems.
- Reinforcing with anchors.
Underground Geological Risks
The main underground risks include:
Land Subsidence and Sinking
Subsidence is a slow-moving process of land sinking that typically does not cause direct casualties but leads to significant economic losses. It can damage constructions and roads, cause flooding in downstream areas, alter land slopes, and lead to groundwater contamination if fissures occur in sewer systems.
Expansive Soil Hazards
Expansive soils swell due to increased water volume, which can destabilize building foundations.
Karst Formation Risks
The unique dynamics and morphology of limestone (karst) soils can generate sudden subsidence or sinking of land portions and even small earthquakes.
Cold Climate and Glacier Risks
Changes in phase (freezing/thawing) cause volume changes in groundwater and rocks, leading to swelling, cracking, landslides, descaling, and disaggregation of blocks or grains. The risks associated with these processes include:
- Snow avalanches
- Soil or rock avalanches
- Landslides
- Collapse of materials
- Changes in volume, porosity, or density of materials
Specific Glacier Hazards
The presence of stable or unstable ice masses largely determines the nature of risks in glacier areas. The most prominent hazards are ice block avalanches and snow avalanches.
Snow and Ice Risks in Spain
In Spain, these risks are prevalent in medium and high mountain areas, and certain low-lying areas with specific latitudes or during very cold winters.
Mitigation and Safeguards
Effective safeguards include:
- Territory planning to avoid structures and activities in high-risk areas.
- Clear signage in identified risk zones.
- Artificially causing controlled avalanches to reduce natural build-up.