Venice underwater amid seasonal 'high water'
Tourists wade across Saint Mark's square in first 'acqua alta'15 October, 14:44
Known as 'acqua alta', or high water, the flooding reached the first level of alarm, or "code yellow", meaning about 8-9% of the city's surface was under water.
Autumn marks the beginning of the high-tide season, when water routinely spills over the city's banks, flooding its streets and squares.
The causes are both natural and man-made.
Decades of pumping groundwater caused significant damage to the delicate foundation before the practice was called off.
Weather experts say the high-water threat has been increasing in recent years as heavier rains have hit northern Italy.
Other possible explanations for the phenomenon include the sea floor rising as a result of incoming silt and gas extraction in the sea off Venice undermining the islands.
According to a recent study, plate tectonics are also to blame as the Adriatic plate is sliding beneath the Apennine Mountains, causing the area to drop in elevation.
Scientists have conceived various ways of warding off the waters since a catastrophic flood in 1966 and a system of moveable flood barriers called MOSE is near completion after years of controversy.