Defining a multi-hazard index in territorial planning framework: application on the Coimbra municipality (western-central Portugal)

In order to support a more integrated approach in the early phases of Risk Management Process, a multi-hazard index was defined to assess the spatial and temporal interaction between natural hazards affecting the same area in a specific timeframe. The Coimbra municipality (western-central Portugal) was used as case study. This territory is an example of the persistent occurrence of potentially dangerous natural events: e.g., floods, landslides and forest fires. Using weighting methodologies, numerical values were assigned to each hazard-related factor (weights) and their categories (ratings). To minimize subjectivity/bias in weighting and rating-assignment processes, several quantitative methods were applied, including probabilistic frequency distribution, multi-criteria analysis and artificial neural networks. Monothematic hazard index quantification and subsequently multi-hazard assessment were implemented in a geographic information system. In few hotspots, the relationship between the observed multi-hazard manifestations and the predicted multi-hazard occurrences was recognized. A framework containing the main hazardous processes and most of the complex relationships/interconnections between them was established. The different degree of multi-hazard zones was mapped. This map can be used to support the implementation of actions to mitigate exposure and vulnerability to these hazards, as well as to promote the territorial management and the development of a resilient municipal system.