Hydrogeology and its effect on slope stability along the coastal aquifer of Nice, France

► We monitor pore pressure in a submarine landslide area (Nice, France) over years. ► Seasonal pressure transients are driven by the hydrology of the coastal aquifer. ► High pore pressure transients cause hydrofracture and seepage. ► Fresh water detected in cored sediments may weaken clayey deposits of the slope. ► Seepage and pore pressure fluctuations favour shear zones and progressive failure.