Chioggia it was now just after low water at Porto di Lido, what had been the principal entrance to the Lagoon and to Venice when it was commonplace to see 60,000-ton tankers wandering about in St Mark’s Basin. This was until they dredged the deep-water channel from Porto Malamocco to Marghera, using the material brought up from the bottom as infilling for the Third Industrial Zone. About now the flood would be beginning to run through Porto di Lido, Porto di Malamocco, and also through Porto di Chioggia, the three entrances that the Magistrates of the Waters had left open centuries ago, having sealed off the others after years of trial and error, by doing so preserving a delicate balance which allowed Venice to function both as a city and a great seaport. Now, for six hours, the tide would flow into the Lagoon, which is not what it appears to be – a single simple expanse of water – but is made up of three distinct basins, each separated one from the other by watersheds known as the spartiacque, spreading through its main arteries and myriad veins, channels so small that no chart shows them, and scouring and filling the canals of the city itself. Then, at the end of the sixth hour, when it was at the full, the tide would begin to run out, loaded with the effluent of the industrial zones, which sometimes includes dangerous quantities of ammonia and its by-products of oxidation, phenol, cyanide, sulphur, chlorine, naphtha, as well as oil from passing ships and boats, all the liquid sewage of Venice, the peculiarly filthy filth of a city entirely without drains, a large part of the solid ordure produced by its inhabitants, and at least a part of that produced by Mestre and Marghera, together with vast quantities of insoluble domestic detergent. One of the more awful sights in the Lagoon used to be a mud bank at Marghera with mountains of ordure rising from it, preserved, presumably for all eternity, or until they burst, in plastic bags. There they waited for an exceptionally high water, an acqua alta, to distribute them over other distant parts of the Lagoon, with thousands of gulls, apparently unable to penetrate them with their beaks, hanging frustratedly over them. All because a large incineration plant, built in the Second Industrial Zone, failed to work.
Twenty years ago the only fish of any size that was indigenous to the Lagoon and which reproduced itself in it was something called the Gò (Gobius ophocephalus), which nested in the mud on the edge of the deep canals. All the others were caught in the open sea and penned in the valli at the northern and south-western ends of the Lagoon. Mussels were also cultivated. Whether it is safe to eat any of these fish today must be questionable. There is no need any more for the Commune to display the warning against swimming on the door of the crumbling open-air swimming place on the Zattere, the long waterfront in Venice facing the Giudecca Canal. It is only too obvious.
The Adriatic performs this operation of filling and emptying the Lagoon four times every twenty-four hours over an area that used to be roughly thirty-five miles long and up to eight miles wide, but is now much less because of infilling and the construction of new valli. That is except during periods of what Venetians call la Colma or l’acqua alta, high water.
Even though the moon was nearly full there would be no acqua alta on this particular night. Acqua alta is not dependent on the tide itself being exceptionally high, or even high. It occurs when the barometric pressure falls sufficiently low to allow the level of the Adriatic to rise on what is a very low coastline, and when the strong, warm, south-westerly sirocco blows up it. If the barometric pressure is low enough and the sirocco is strong enough at the time when the ebb is beginning in the Lagoon, the water is penned inside it, unable to get out, and when the next tide begins to press in through the three entrances, the Porti, and is added to the high water already there, the natural divisions between the three basins of the Lagoon, the spartiacque, cease to exist and Venice and many other islands, inhabited and uninhabited, are flooded. Other factors can make the acqua alta even higher – heavy rain, a full moon, something called the seiche, the turning of the Adriatic on an imaginary pivot – but the sirocco and a low barometer are the two indispensable conditions.
This is not a new phenomenon. The records of the acqua alta from the thirteenth century onwards are full of entries such as ‘the water rose to the height of a man in the streets’ (on 23 September 1240); ‘the water rose from eight o’clock until midday. Many were drowned inside their houses or died of cold’ (in December 1280); ‘roaring horribly the sea rose up towards the sky, causing a terrible fear … and with such force that it broke the Lido in several places’ (in December 1600).
In 1825, the murazzi, neglected since the fall of the Republic in 1797, were breached during an enormous storm, but were made good again. On a day in 1967, the first year in which accurate measurements were kept, the water rose five feet above the average sea level. In the forty-seven years between 1867 and 1914, only seven exceptionally high waters, those more than three and a half feet above the normal level, submerged the city; but in the fifty years between 1917 and 1967 Venice sank beneath the waves more than forty times, an extraordinary increase, so that looking at a vertical graph of these high waters during the period from 1867 to 1967 the lines representing them appear as eight more or less isolated trees between 1867 and 1920, some thick clumps in the thirties, late forties and early fifties, and a dense, soaring forest in the late fifties and sixties. The longest line of all is the one showing the acqua alta of 4 November 1966.
During the night of 3–4 November, the sirocco blew Force 8, the barometer fell to around 750 mm, there was continual heavy rain and waves twelve feet high roared in over the Litorali, submerging Cavallino, the northernmost one, smashing the elegant bathing establishments on the Lido and hurling aside the outerworks of the murazzi on Pellestrina, the great boulders piled fifteen feet high, then breaching, in ten different places, the walls themselves, composed of huge blocks of marble six feet long, but on which no proper repair work had been done for more than thirty years. This time the water at Venice rose six and a half feet above the average sea level, and the result was spectacular.
It poured under the 450 or so bridges (scarcely any Venetians, let alone outsiders, agree about the number of bridges in the city, or any other of the following figures), overflowing the 177 – some say 150 – canals, the rii, 46 of which are branches off the Canalazzo, the Grand Canal, inundating the 117, or 122, or whatever number of shoals or islands on which the city is said to be built, the 15,000 houses in which large numbers of people were living on the ground floors in the six sestieri, or wards, into which it is divided, and the majority of the 107 churches, of which 80 were still in use. It also inundated 3000 miles of streets and alleys, the various open spaces, the campi, so called because they were once expanses of grass, the campielli and the piazzette, not to speak of the only Piazza, St Mark’s, with an unimaginably vile compound of all the various effluents mentioned previously in connection with the Lagoon. To which was added diesel oil and gas oil which had escaped from the storage tanks, leaving the city without electric light, means of cooking or heating, or any communication with the outside world, not to speak of the awful, immense, much of it irreparable, damage done to innumerable works of art.
The acqua alta persisted for more than twenty hours. The most dangerous moment came at six in the evening, when the water reached the highest level ever recorded. This was the moment that the Venetians call the acqua morta, when it should begin to go down but doesn’t. By this time the glass was down to 744 mm and if at this moment a fresh impulse had been given to the waters by the sirocco, forcing it to yet higher levels, Venice might well have collapsed. As it was, a miracle occurred. The wind changed. It began to blow from the south-west, a wind the people of Venice and the Lagoon call the vento Garbin, and by nine o’clock that night the waters began to fall and the city was saved, at least for the time being.
Long before we stepped ashore from the steamer on to Riva degli Schiavoni, the great expanse of marble quay off which Slavs from the Dalmatian coast used to moor their vessels in St Mark’s Basin, darkness had added itself to the fog, creating the sort of conditions that even Jack the Ripper would have found a bit thick for his work down in nineteenth-century Whitechapel.
The fog dissipated what had seemed a romantic possibility when we left Chioggia but now seemed a crazy dream, that we
