Conceptual and numerical modelling for hydrogeological hazard assessment in the UNESCO site of Castelseprio (Northern Italy)

This paper deals with the evaluation of the hydrogeological hazard in the archaeological site of Castelseprio (northern Italy). Based on the geological, hydrogeological and geomorphological setting of the site, the failure modes and their causative factors were identified, and a proper conceptual model was reconstructed, identifying piping processes as the main phenomena ruling the slopes evolution and the landslides triggering. Afterwards, the hydrogeological hazard was assessed applying numerical modelling both in 2D and in 3D. In particular, the 2D analyses were aimed at simulating the triggering phenomena leading to instability, with particular reference to the influence of piping initiation and propagation. Numerical results in 2D showed a dependence of the stability conditions on the rainfall intensity, whose increase brings about a significant widening of the zones prone to piping. Based on the results of the 2D simulations, a 3D model was implemented in order to evaluate the stability conditions in the different zones of the study area. The results of the 3D simulations allowed mapping the hydrogeological hazard and identifying the best practices for the future development of the UNESCO site, in order to guarantee its unity as well as its safety.