Why is Venice sinking?

Venice was built on wooden piles driven into mud and clay in a lagoon, and these sediments naturally compress over time. In the 20th century, pumping of groundwater for industry greatly sped up subsidence until it was banned in the 1970s. Today the city sinks only a few millimetres a year, but rising seas make flooding, known as acqua alta, more frequent. In November 2019 a tide of 187 cm caused severe flooding. The MOSE system of 78 mobile flood barriers at the lagoon inlets began operating in 2020 and has since protected the city from many high tides.