Acqua Alta is a Venetian tidal phenomenon that happens mostly in winter but can happen at any time of year. It is tidal because it reaches it’s peak at a certain time and then goes down. The water comes in and it goes out. It is affected by a variety of factors including winds coming from a certain direction that do not allow the tidal water to flow back out to sea, barometric pressure, moon phases, storms etc. Some of my “facts” can be a little simplistic because I am not an expert. Rain is not the cause and it is not flooding like a storm surge or like when rivers overflow their banks and the water stays for days. It tends to be high for a few hours and then goes back down.
This webcam in Piazza San Marco (one of the lowest areas of the city) shows that at 9:50 am there is still some water in the Piazza.
http://www.hotelconcordia.com/webcam-en/
No water even attempted to enter my apartment. I know because I think I was up every hour checking. The pictures I took at 4:30 am did not turn out but here are a few later in morning.
1 and 2: 6:34 AM
3 and 4. 7:41 am
No boats have attempted to go under that bridge. And yes, it’s still pretty dark here at that time of the morning.
5, 6, 7 and 8…8:30 ish
9, 10, 11, and 12 between 8:53 and 9:19
This is the metal gate or as Sebastiano called it when he installed it in the door last evening “high tide guard”…don’t know what it is called in Italian. I should have asked him.
As you can see over the course of about three hours it has not gone down much. The next high tide is 90 cm at 17:00…or 5 pm.
I think I’ll check and see if I have the strength to unscrew the “gate” and put it away.
Meandering with Misha 
The “gate” has been removed and stored for next time. I had no trouble doing it myself.
Glad to hear you’re safe and sound. Thanks for the great explanation about the tides. This is somethng that seems quite often insufficiently explained by the media when they report about the flooding in Venice. Maybe I am wrong.
Wish you a nice and restful day if you need it.
Ciao from Vienna
Liz
Ciao Liz,
Yes, a lot of the media reports make it sound like all of Venice is under water for days.For the most part it is only the very low lying areas that get significant water in the calles. I know that is how they depict it in the US and use pictures that are at least a week old and show people attempting to swim in San Marco. It is hard if you are only here for a few days and have limited time to sight see and part of that time is several hours of acqua alta. But as I have said before….the Venetians have been dealing with this for centuries.
Needless to say I did not sleep straight through the night…just getting up every now and then to make sure everything was okay. I may have a nap this afternoon, but then again just may go to bed early tonight.
M