GIS approach for preventive evaluation of roads loss of efficiency in hydrogeological emergencies

The theme of the simulation of hydrogeological risk with GIS technology is analyzed with focus on the modeling of the architecture of a Spatial Data Base to support risk analysis and on the construction of a specialized frame with free and open source software. For this purpose a model of analysis of the vulnerability of roads developed by (Cafiso et al., 2002) has been adopted. The case of study is represented by a seismic land characterized by steep slopes and frequent instability phenomena. In detail, the area of interest is a mountainous land in Sicily with a city, Enna (about 30 000 people), that lies on the top. The access to the city is assured by few and very winding roads which are also highly vulnerable to seismic and hydrogeological hazards. The loss of efficiency of these roads for exceptional rainfall events should compromise timeliness and effectiveness of rescue operations. The data of the sample area have been implemented in the specialized GIS appositely constructed in order to forecast the possible damage to roads and the results of some simulations have been related to the effects registered after some extreme events, obtaining useful indications for the validation of the approach.