Groundwater rebound and flooding in the Naples' periurban area (Italy)

Groundwater bodies in the urbanized and densely populated aquifers or coastal floodplains may be subjected to groundwater rebound (GR), often causing serious risks of groundwater flooding (GF) to underground structures and infrastructures. This paper shows the results of a study carried out in the Naples' periurban area (Italy) to: investigate the dynamics and features of GR and GF phenomena, map flooded sites during 2013–2015 period, and provide an interpretative analysis of the factors that control the GF of private buildings and agricultural lands. At the municipality scale, since 1990 and until 2015, a remarkable and widespread GR was observed, with magnitude up to +16.54 m, triggering an unexpected GF of basements of buildings and agricultural soils. Field surveys proved that there is a time delay of the GF, ranging from 17 to 20 years, compared to the start of GR. Moreover, inhomogeneous distribution of flooding episodes is controlled by anthropogenic and natural factors. The obtained results are fundamental to design mitigation measures to GF hazard, and offer new perspectives to make Naples' periurban area more robust, smart and resilient against this new hydrogeological risk, undervalued by Italian legislation and local authorities.