The canals, which form much of its transport infrastructure and carry thousands of gondolas, launches, barges and water buses, are tidal and therefore constantly changing. High tide levels mean reduced headroom under bridges and the city's transportation may need to re-route. When pavements and other pedestrian areas disappear under water, raised walkways may need to be erected. The city's population and its large number of commuters are used to this, but accurate, timely information about the tides is important so that changes are made to keep daily life on track.
Technology is used in a number of ways to inform the city about water levels, including a website, a toll-free phone line and even a smartphone app. There are also a number of touchscreen information points at newspaper kiosks around the city. An old siren-based audio system had also been used for many years but it was increasingly less reliable, due to mechanical deterioration, and it could only broadcast one alert signal.
The Previsioni E Segnalazioni Maree (Tidal Forecasting and Signalling Centre) is the local government department charged with monitoring and predicting the water levels and communicating them to the city. They identified four different tidal bands: the lowest, 110-120cm above normal sea level, affects 12% of the population, while the highest at 140cm and above affects as much as 90%. If the water rises beyond 190cm it impacts the city's entire population. This banding defined a multi-level requirement for the warning system.
The new multi-tone audio system uses a specially developed version of Community's R.5 loudspeaker, designed precisely for the power, frequency response and dispersion required. Size was also critical in being able to deliver and mount the loudspeakers in some of the ancient towers where they were to be deployed. Located in fifteen bell-towers in central Venice and at a further fifteen locations on outlying islands, the loudspeakers play a series of alert and musical tones that inform residents of the coming tidal levels.
(Jim Evans)
