Environmental Impact, Natural Risks and Management
This domain integrates everything else: how impacts are predicted, how risk is quantified, how land-use planning reduces exposure, and what sustainability means in practice. PAU questions are usually decision-based - given a project or a hazard map, argue a position with explicit criteria.
Environmental impact assessment
EIA identifies, predicts and mitigates impacts before authorisation. It covers direct and indirect, cumulative, reversible and irreversible, and temporary and permanent effects on air, water, soil, biota, landscape and heritage. The mitigation hierarchy is strict: avoid, minimise, restore, then compensate. A monitoring programme and public participation are mandatory parts of the process. Environmental impact assessment applies to a project; strategic environmental assessment applies to plans and programmes.
Natural risk
Risk = hazard × exposure × vulnerability. Hazard is the probability and magnitude of the event; exposure is what is in the way; vulnerability is how easily it is damaged. Return period T and annual exceedance probability relate as P = 1/T (a 100-year flood has a 1% annual probability, not a guarantee once per century).
Principal risks in Catalonia
- Floods: torrential coastal floods, Ebro Delta subsidence; mitigation by floodplain zoning, permeable surfaces, green infrastructure, and flood warning.
- Slope instability: Pyrenean and Pre-coastal Range landslides; mitigation by drainage, terracing and vegetation.
- Seismic risk: Pyrenean fault zones; mitigation through building codes rather than prediction.
- Volcanic risk: the Quaternary La Garrotxa field; monitoring of gases and seismicity.
- Coastal erosion: caused by sediment starvation after river damming plus sea-level rise; mitigation by controlled sediment inputs and managed retreat.
- Wildfire: Mediterranean summer drought plus fuel accumulation; mitigation by strategic fuel breaks and prescribed burning.
Planning and sustainability
Land-use planning is the cheapest and most effective prevention tool: keeping housing and industry out of high-risk zones converts a hazard into a manageable event. Sustainability balances extraction and regeneration, uses the circular economy, applies the polluter-pays and precautionary principles, and depends on the SDGs and protected-area networks (PEIN, Natura 2000).
Worked example
A hotel is proposed on an eroding beach at the Ebro Delta. Risk rises because the delta is subsiding and sediment supply is trapped behind dams upstream; hazard (coastal storms, sea-level rise) is increasing, exposure is high, vulnerability is high because of the low platform. Reasoning: this is an avoid case, not a mitigate case. Compensation by sand nourishment would be temporary; managed retreat plus sediment restoration inland is the defensible option, with public participation and monitoring.
Traps that cost marks
Defining risk as hazard alone; stating that a 100-year flood happens every 100 years; using compensation as the first option; confusing prediction of a hazard with prevention through planning.