Acqua alta hits Venice

(ANSA) - Venice, October 29 - The first high water of the autumn hit Venice Monday and sirens blared across the lagoon city as the 'acqua alta' passed the 110 cm above sea level at which citizens are alerted to the phenomenon.
    The water level was measured at 149 above sea level, a measure at which 70% of the city centre is flooded.
    It is set to hit 160 cm at about 15:00, local officials said.
    Levels of 100-120 cm above sea level are fairly common in the lagoon city and Venice is well-equipped to cope with its rafts of pontoon walkways.
    But anything much above 120cm risks swamping the city and washing the walkways away.
    The high-water threat has been increasing in recent years as heavier rains have hit northern Italy, weather experts say.
    Scientists have conceived various ways of warding off the waters since a dramatic 1966 flood, and a system of moveable flood barriers called MOSE is being installed after years of rows.
    Experts say there are three main reasons for high water in the city: the rising floor in the lagoon caused by incoming silt; the undermining of the islands by the extraction of methane gas in the sea off Venice; and the overall increase in sea levels caused by global warming.