Hydro-geotechnical modelling of subsidence in the Como urban area

The urban area of Como (Italy) is particularly susceptible to subsidence. The reason is the particular structure of the subsoil, combined with the anthropic modification of the lakeshore lands linked to the historical evolution of the area. Moreover, this phenomenon exposes the lakefront areas to an increasing risk of flooding. The primary purpose of this study was to develop an effective methodology for the assessment of subsidence in urban areas, to be used as a support in groundwater management. The development of a coupled hydrogeological-geotechnical numerical model for the period 2004-2011 allowed recognizing the shoreline results as most susceptible areas to the phenomenon. Model results were critically evaluated through comparison with time series of PSInSAR and high precision levelling data available in the area. The anthropic perturbations of groundwater flow linked to the construction of lake flooding defenses in 2008-2009, enhanced the subsidence phenomenon in a localized area, pointing out the strong inter-dependence of groundwater circulation, lake level oscillations and geotechnical behavior of soils. Thus, the model revealed the most critical zones and geotechnical units, demonstrating to be a potential powerful tool to predict subsidence scenarios (e.g. the future completion of the floods defense works in the shoreline area).