154 Sea Level Processes and Effects of Sea Level Change
Fig. 5.23. The flooding of San Marcus Square by more than I m in November 1966.
[Photo courtesy A. Stefanon. Venice]
In the last 20 years the groundwater level was lowered by 5 m in and around
Venice , by 20 m in the industrial zone of Marghera. During this period, subsidence
accelerated markedly. Perhaps this factor alone can account for the high sinking
rates.
5. For the last 100 years the sea level has been rising globally globally by I to 2 mm
per years as mentioned in Section 5.3.1 and illustrated in Fig. 5.22.
6. The normal tidal range is about 1 m at Venice. Storms can increase a high tide
level considerably. On November 4, 1966, a storm tide reached + 1.9 m, flooding
the San Marcus Square (Fig. 5.23). Normally, the lagoon would act as a buffer
receiving the incoming water from the Adriatic Sea. However, large parts of the
lagoon were filled above sea level to gain land for industrial purposes. The lagoonal area therefore is only about 70 % of what it was some 200 years ago.
Shipping channels were deepened partly to more than 12 m. The concern that
these actions will increase the influence of storms and storm tides appears justified.