Flood risk: a new approach for roads vulnerability assessment

A new approach to assess roads vulnerability in flood events is here presented. The main results of a case study, the road networks in Tiber floodplain, are also discussed. The new analytical model is based on Multi-Criteria Analysis (MCA) that assigns a vulnerability value to each road element (embankments, viaducts,..) depending on its structural and functional characteristics. Thanks to the specific framework of the model, also vulnerability causes can be easily determined enabling decisions makers to create meaningful future scenarios and to explore different strategies for an efficient vulnerability, and so risk, mitigation. Showing the effects of strategic alternatives in the long-term, this model allows a new wider and sustainable approach in flood risk management. Here the new approach has been used to assess roads vulnerability and risk, and then, to draw out vulnerability and risk maps. These maps are fundamental in emergency planning. The study also shows how the model could represents a useful decision support tool enabling decisions makers to determine evacuation possibilities and potential shelters, as shown in the Monterodondo case here presented. Using the maps, points of weakness in the area have been pointed out: these are especially viaducts crossing the river. On the other hand, using the model as a checking tool, different vulnerability mitigation measures have been planned and checked for critical elements, as shown in the example of the SP18a ‘Via Traversa del Grillo’ viaduct.