Coupled ground uplift and groundwater rebound in the metropolitan city of Naples (southern Italy)

Subsidence and ground uplift are phenomena that may have natural or anthropogenic origin and cause strong socioeconomic and environmental impacts, especially in urban areas. In this paper, the coupling between ground uplift and groundwater rebound in a complex multi-layered aquifer system in the metropolitan city of Naples (southern Italy) has been investigated. By an integrated use of hydrogeological and DInSAR monitoring data covering the periods 1989–2013 and 1993–2010, respectively, the spatio-temporal evolution of natural ground deformation following the strong reduction and interruption of groundwater pumping has been analysed. Hydrogeological monitoring data have shown large-scale groundwater rebound, with the highest amplitude of approximately 16m and a groundwater rising velocity up to approximately 1.0 m/yr. DInSAR data show a general ground uplift with a magnitude of approximately 40mm on average, except for the southern sector of the study area where some local natural and human-induced subsidence has been identified. A comparison between trends of groundwater level and ground displacement indicates that the ground uplift is linked to a poro-elastic rebound mechanism in the porous aquifer system, which is triggered by the increase of pore pressure, while the rate of ground displacement is controlled by the hydrostratigraphic characteristics of the multilayered aquifer system. The results improve the knowledge of man-induced deformation in complex urban aquifers affected by groundwater rebound and highlight that the implementation of an appropriate hydro-mechanical deformation model is a necessary step to correctly model and manage a new geohazard in a highly urbanized environment.