An Integrated Model for the Assessment of Subsidence Risk in the Area of Bologna (Italy)

The rapid and uncontrolled evolution of urban and industrial settlements often turns to be unsustainable for the natural and anthropic system. A prominent example is the subsidence induced by intensive groundwater exploitation. Assessing the risk produced on urban agglomerations by the groundwater table drawdown enables to visualize the impact and to undertake policies that protects structures, infrastructures and, more generally, the sociohistorical- cultural environment of the cities. This task implies to assemble hydrological, hydrogeological and geotechnical factors into comprehensive models that lead to compute free field deformation. Interfacing this effect with the mechanical characteristics of buildings or infrastructures allows to quantify damage severity. The present paper reports a study carried out for the city of Bologna, one of the most emblematic examples in Italy, whose old town and suburbs have undergone an extensive and continuous subsidence from the early seventies. An integrated risk assessment methodology is implemented defining the paramount factors, intensity measures, engineering demand parameters, vulnerability and exposure and building an interpretative model based on observation.