Integrated spatial flood risk assessment: The case of Zaragoza

Flood-risk prevention measures are designed to reduce the adverse consequences associated with floods for humans, the environment, cultural heritage and economic activity, as per the EU Floods Directive (2007/60/EC). An economic assessment of the risk provides advantages for the identification of single hazards. Policy makers thus receive relevant information on the sectors and places at risk. This article provides an integrated spatial assessment of the flood risk for human beings and for the residential, non-residential, agricultural and environmental sectors. The methodology used is applied to the city of Zaragoza and downstream municipalities in the Ebro river basin (Spain). The analysis emphasises that flood-risk assessment must account for two measures of risk. The first is the expected annual damage, which is used to prioritise locations and sectors for prevention. The second comprises damage-probability curves, which provide information on the distribution of the risks, taking into account whether they originate from frequent floods with slight consequences or from exceptional floods with major consequences. The spatial assessment of risk reveals how the risk is distributed between upstream and downstream cities. This opens up a discussion on the issue of equity in flood risk-sharing in spatially integrated analysis.