A record year for acqua alta in Venice: high water events doubled compared to 2017

Data show that for the first time in history there were two “exceptional” high levels in the same day, on 29 October. The annual average level (35 cm) is the fourth highest ever.

2018 was a challenging year for high waters, and not only because of the number of events recorded. It’s hard to forget the extraordinary surge of 156 cm recorded on 29 October, during the same days when storms cut down large areas of the Northeast. But in general the levels during the past 12 months were elevated. In Venice there were 121 high water events (between 80 and 110 cm) – almost double those recorded in 2017. Tide levels over 120 cm (but under 140) were recorded 9 times. Then there are the 2 instances of exceptional high levels. These data were released today by the Center for Tide Warnings and Predictions of the City of Venice regarding high water activity in 2018.

Record Numbers

There are still other important numbers: some measures, in fact, have even exceeded those of the terrible flood of 4 November 1966. The records that were recorded: it is the first time in history – since records started being kept in 1872 – that two exceptional tide levels were recorded in the same day, on 29 October with 156 cm at 2:40 PM and 148 cm at 8:25 PM. Again on 29 October the highest low tide in history was recorded with 119 cm at 5:35 PM. Previous high low tide events occurred in 2012 with 117 cm and in 1966 with 116 cm. The highest water level recorded on 29 October, 156 cm, is the fourth highest level ever recorded, and equal to the level recorded at the beginning of December 2008; the others are 194 cm, on 4 November 1966, 166 cm on 22 December 1979, and 159 cm on 1 February of 1986. Again on 29 October, the second highest weather driven sea level rise was recorded, curiously also at 156 cm, the same value that was recorded just hours earlier for the high tide. The highest was in 1966 with 184 cm, the third highest in 1979 with 129 cm.

Annual average level fourth highest ever

The average annual water level was 35 cm over the base level measured at Punta della Salute: a number that is almost 7 cm higher than that of 2017, and is overall the fourth highest in history. As far as meteorological measures go, these reveal that the average annual temperature in the historic center of Venice registered at about 15.9˚C, almost a full degree higher than recorded in 2017, but absolutely among the average of those recorded for the past 10 years. In recent years the average annual temperatures have been recorded as 16.4˚C in 2012 and 16.3˚C in 2014, while 15.9˚C was the average for 2018 as well as 2009, 2011, 2015 and 2016.

The month in 2018 with the highest rainfall was March, the second highest for the past 20 years (or really since the Tide Center has measured rainfall in the city center) both for the cumulative precipitation (the sum of all rainfall in the month) which reached 144mm, and for the number of days of rain, in this case 13.

The strongest gust of wind for the year was also recorded on 29 October, at almost 116 km/h, from the direction of the scirocco, one of the highest values ever recorded in history for winds coming from the southeast.

Source: Venezia Today, 4 January 2019

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