Performance‐Based Planning to Reduce Flooding Vulnerability. Insights from the Case of Turin (North‐West Italy)

Climate change is impacting urban areas with greater frequency and exposing continental cities located on floodplains to extreme short-duration rainfall events (cloudbursts). This scenario requires the development of site-specific flooding vulnerability mitigation strategies that improve local knowledge of flood-prone areas at the urban scale and supersede the traditional hazard approach based on the classification of riverine buffers with a predicted return-period. Moreover, decision-makers need to adopt performance-based strategies for contrasting climate changes and increasing the resilience of territories based on spatially explicit vulnerability assessment. The research develops and tests the recent Flooding Risk Mitigation model of InVEST (Integrated Evaluation of Ecosystem Services and Trade-off) created by the Natural Capital Project where cloudburst vulnerability is the result of interaction between land use and soil hydrological conductivity. It is based on the assumption that during cloudburst events all saturated soils have the potential for flooding which creates water streams regardless of the distance to rivers or channels, causing damage and in the worst cases victims among the population. The output of the model gives the run-off retention index evaluated in the catchment area of Turin (Italy) and its neighbourhoods. We evaluated the output to gain specific insight on potential land use adaptation strategies. The index is the first experimental GIS biophysical assessment developed in this area and it can prove useful in the revision process of the General Town Plan underway.