How did groundwater extraction and channel deepening increase Venice’s flood risk?

Groundwater extraction and channel deepening have significantly increased Venice’s flood risk by contributing to the lowering of the land level relative to the sea.

• Groundwater Extraction: The overextraction of fresh water from mainland aquifers led to local subsidence of the Earth’s crust. This process caused the islands to sink, effectively reducing their elevation and making them more vulnerable to rising water levels. By the 1970s, the islands were sinking at an estimated rate of 1.2 inches every 10 years; however, efforts to utilize external water supplies have since allowed groundwater pressure to rise, which helped stabilize the sinking.12
• Channel Deepening: The deepening of lagoon channels during the 20th century altered the hydrodynamics of the area. This modification, combined with the geologic sinking of the Po River basin and the rising level of the Adriatic Sea, has exacerbated the city's flooding problem, leading to more frequent acqua alta (high water) events.1

These human-induced changes have compromised the city's natural defenses, leaving Venice increasingly susceptible to inundation during high tides and severe weather.1