Natural hazards, environmental impacts and risk management
This domain links natural processes to human consequences. The PAU expects the risk equation, a specific Spanish hazard example, and a management strategy that distinguishes prediction, prevention and mitigation.
Core concepts
Risk = hazard × vulnerability × exposure, where hazard is the probability of a damaging event. Vulnerability covers physical, social and economic fragility; exposure is the value located in the hazardous zone. A hazard becomes a disaster only when it meets vulnerable, exposed populations.
Hazards in Spain
- Seismic: the Betic cordillera and the Pyrenees; the 2011 Lorca earthquake (magnitude 5.1) caused nine deaths through vulnerable masonry.
- Volcanic: the Canary Islands, including the 2021 Tajogaite eruption on La Palma.
- Floods: Mediterranean torrents and ramblas, flash floods in the Júcar and Segura basins.
- Mass movements: landslides in steep marl and flysch terrain.
- Karst collapse and sinkholes in evaporite and limestone areas of the Ebro and La Mancha basins.
- Drought, coastal erosion and desertification in the southeast.
Impacts and management
Environmental impact assessment predicts effects and proposes corrective measures, often using Leopold-type matrices. Mitigation includes land-use zoning, building codes, early-warning networks, reforestation of headwaters, check dams and the flood-risk maps required by the EU Floods Directive.
Worked example
Two towns face the same 1-in-100-year flood. Town A has floodplain housing and no warning system; Town B is built above flood level with a warning plan. Reasoning: the hazard is identical, but exposure and vulnerability differ, so risk is far higher in A; reducing exposure through zoning cuts risk more than any measure aimed at changing the hazard itself.
Traps that cost marks
- Using hazard and risk as synonyms.
- Claiming zero risk is achievable, or that a 100-year event occurs exactly once a century.
- Blaming a hazard for a disaster without discussing vulnerability.
- Confusing prevention (avoid exposure), prediction (forecast) and mitigation (reduce damage).