Venice has been hit by its highest winter floods in two years with water rising to 140cm (56in) above sea level and meteorologists are warning that heavier flooding will be the rule rather than the exception in the coming years.

Tourists have had to wade through flooded parts of the city in Wellington boots and cross the landmark St. Mark's Square via wooden walkways after days of torrential rain. The square was said to be under 60cm of water.

The phenomenon, known as "acqua alt" or "high water" is common in Venice at this time of year but levels are higher than last winter and experts say things will get worse in the future. The city experienced its worst flooding in decades only four years ago when 160cm of floodwater was recorded.

Italian news agency Ansa classified the situation as "exceptional", with shops, basements and buildings flooded.

People walk in a flooded street during a period of seasonal high water in Venice
People walk in a flooded street during a period of seasonal high water in Venice (Reuters)

While the canal city is used to high waters, they are putting its fragile infrastructure under heavy stress.

The administration has put in place a system of moveable barriers, the Mose, which will rise from the seabed to protect Venice from high tides. The system will not be operational before 2014, however.

"Italy is currently under a nationwide rainstorm and autumn marks the beginning of the high-water season, which has been particularly severe this year," reported Gazzetta del Sud online.

"The causes are both natural and man-made. Decades of pumping groundwater caused significant damage to the delicate foundations 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.