The leading expert on hydraulic engineering speaks in commission on the issue of maintaining buildings: “The situation is dramatic”
By Eugenio Pendolini
12 October 2022
It was 1992 when Luigi D’Alpaos, professor of hydrodynamics in the Dept. of Engineering at Padova, released a report denouncing the risks of moto ondoso (waves from boats) in Venice and the possible solutions, starting with the reduction of speeds.
Thirty years later, D’Alpaos returned to a conciliar commission, the fourth and fifth convened by Deborah Onisto, to speak about the same unresolved problems.
“The fundamental parameter is speed,” D’Alpaos told the commission, “the damage produced, we have established following some experiments, travels at the cube of velocity, so if a boat is going two meters per second, the energy of the wave motion will be eight times as much”.
This is the ill of the lagoon. There are other possible useful measures, such as, for example, concerning propellors and the shapes of keels, but the primary solution to the problems that have continued for thirty years is to act on controlling speed, even if “it could annoy certain categories, which is the reason that the studies from 1992 have been put on some high shelf in a few bookstores”.
For D’Alpaos the number one need is for behaviors that are appropriate in the lagoon, both to protect the surrounding environment as well as the foundations of the homes. “They are perforated, the action of the waves is dramatic”, explains D’Alpaos, “because it erodes and extracts sediments with the impacts, and this requires a great deal of maintenance, which we had in the past, but now it seems as if no one cares. Today you can dig when wet, but it had a greater impact to dry the canals for repairs”.
Regarding this point, in the commission councilor Marco Gasparinetti (Terra e Acqua) announced the presentation of a dossier with reports of the city foundations badly reduced and at risk of collapse.
The real problem, however, remains that of controls. “Those who govern the city – today as in the past – do not want to antagonize the categories, and many of these demand traveling fast, perhaps even faster”, attacked Giovanni Andrea Martini (Tutta la Città Insieme).
If the problem of GPS on board the boats regards not so much the instrumentation as the ability to trigger fines, as explained by president Deborah Onisto, for D’Alpaos the necessity is that the controls correspond to definite fines that are safely protected from appeals and annulments. Then there is the need to understand the problems of the lagoon.
“You cannot send technicians to Venice who do not posses an understanding of the lagoon’s problems”, said D’Alpaos, “adequate preparation is required. The tradition of the Magistrato alle Acque was that the best inspectors, who had spent their lives within the structure, would become president”.
Finally, a comment on the Canale dei Petroli and cruise ships: “We risk the silting of the canal, erosion of shallow water areas and the loss of a fraction of the lagoon”.
Source: La Nuova di Venezia e Mestre