Acqua Alta, some practical advice.
The phenomenon of high water is a peculiarity of some areas of the Adriatic Sea, but Venice is its global icon. Acqua alta refers to the rising of the water in the lagoon that affects certain areas of the city. It usually occurs between autumn and early spring with peaks in November. This phenomenon lasts on average a couple of hours and resolves naturally.
If you hear sirens, however, then that is the warning of "very sustained" high water, usually above 110 cm. The areas that flood most easily are those in the San Marco district as they are the most exposed to the sirocco winds (south, south east). These winds can reach up to 25 km per hour. High water is monitored daily and can be measured here.
Coping with Venetian high water is not that difficult, you just need waterproof rubber boots, possibly high. If you don't have boots we recommend you to put on plastic bags and tie them with elastic bands. Many Venetians use this ingenious stratagem.
The Venice City Council installs walkways in advance to deal with the problem, so you'll have very few hiccups on your schedule. Even the vaporettos can be affected with small changes to their routes, but nothing impactful. We advise you to avoid the most flooded streets by taking alternative routes or by taking a vaporetto even if only for one stop.
Acqua Alta, some simple theoretical background
Acqua alta is the result of a series of astronomical phenomena, such as the movement of the moon and partly of the sun. The position of the lagoon basin exposes it to the strong scirocco winds, increasing the rising effects. The flooding of the Po and Adige rivers also indirectly creates effects on high water.
Human beings have directly influenced this phenomenon. One example is probably the creation of Porto Marghera and the subsequent loss of the "barena" islands that acted as a limit to high water. The various bridges built in the lagoon did not help Venice either. It is certainly a complex phenomenon and difficult to schematise.
The Venice City Council has tried to contain the problem by creating a system of mobile dams called Mose, which began in 2003. Still not finished. Its function is to stem the excessive inflow of water through inlets in the sandbanks of the lagoon.
The phenomenon of high water is unique and will not be easy to solve. High water will probably always accompany Venice, for better or for worse.
You can get more information regarding high water information by calling the number 0412411996