The term 'acqua alta’ (Italian for ‘high water’) commonly refers to the exceptional tidal peaks, which occur periodically in the northern Adriatic Sea, especially in the Venetian Lagoon, and cause flooding. The phenomenon occurs above all in the autumn-spring and with particular meteorological conditions when the sirocco winds coming from the Otranto channel prevent the regular flow of water, or when the bora winds obstruct the outflow of the lagoons and of the rivers of the Veneto coast. The population is alerted when this is forecast.

Surveys and official communications are handled by the ICPSM of the Municipality of Venice (Istituzione Centro Previsione e Segnalazioni Maree).

Based on the updated tide levels received from the ICPSM, AVM/Actv Navigation Operating Center applies an Operative Plan well in advance of the tide levels being reached to guarantee safe waterborne services. In the event of high tide levels, AVM/ACTV will apply changes to the waterborne public transport routes to guarantee a service, except in the case of exceptional tides.  Nevertheless, any assessment to continue the trip safely is always at the discretion of the master of the vessel as well as any consequent restrictions along the route with respect to the rescheduled timetables.

AVM/Actv will inform of any changes to the services through the corporate social media channels @muoversivenezia, the user-info panels at the waterbus stops, through the DIME call center 041 041 and the Infomobilità page.

Tide level above 85 cm

The route from S. Marcuola to Rialto/S. Marco (St. Mark’s) is suspended due to difficulties in reaching the waterbus stop.

Tide level above 95 cm

The routes are divided and rerouted as follows:

Route 2: limited to San Zaccaria "B" - Tronchetto via Canale della Giudecca and San Marco (St. Mark’s) - P.le Roma via Canal Grande, shuttle boat service up to a tide level of +135 cm, then or alternatively with substitute bus service for P.le Roma - Tronchetto. In addition, the People Mover, which runs every 10 minutes can be used for the same route.

Routes 4.1 and 4.2: limited to San Zaccaria "B1" e "G" stop at “B” - Ospedale - F.te Nove - Murano - Tre Archi and vice versa with the omission of the San Zaccaria - Giudecca - P.le Roma - Ferrovia (Railway Station) - Tre Archi service and vice versa. A substitute shuttle bus service will be operating between P.le Roma and Santa Marta and shuttle boat service between Santa Marta and Sacca Fisola

Route 5.1: limited to Lido S.M.E. "A" – Ospedale (Hospital) - F. Nove - Tre Archi and vice versa

Route 5.2: rerouted via Canal Grande and limited to P.le Roma - Lido S.M.E. "A" and vice versa

Route 6: rerouted via Canal Grande and limited to P.le Roma - Lido S.M.E. "B" and vice versa

--> At Ferrovia (Railway Station), Routes 51./5.2 stop at waterbus stop the "C" to P.le Roma and waterbus stop "D" to Lido

Route 3: SUSPENDED

all the other routes are normal

The night services from 08:00 pm to 07:00 am running from Murano Colonna waterbus stops "A" and "B" will be suspended.

Tide level above 120 cm

In addition to the previous provisions for tide levels above 105 cm, Zattere will be suspended in the San Marco (St. Mark’s) - Lido direction as there will be no connecting gangplanks.

Tide level above 125 cm

In addition to the previous provisions for tide levels above 120 cm, the entry gangplanks to the structures and the point of sale in Rialto Route 2 (waterbus stops "C" and "D") will no longer be accessible. Access to the structures from the exits up to 140 cm will be maintained.

Tide level above 135 cm

Transit under the Vivarini bridge of Murano is prohibited and therefore connection of routes 4.1 / 4.2 in the Colonna-Venier section (Via Serenella) will be suspended. This plan will be maintained up to a tide level of +140 cm

Tide level above 140 cm

The public transport service will be suspended as a whole and connection to the islands will only be possible from the structures that remain accessible.