Malamocco Marghera Channel in Venice: enhanced traffic, more safety and protection of the Lagoon
The North Adriatic Sea Port Authority presents the results of the international research project “Channeling the Green Deal for Venice”.
Venice, Sept. 21, 2023 – The North Adriatic Sea Port Authority presented today in the context of the first Sustainability Biennial promoted by FVCMS/VSF the conclusions of “Channeling the Green Deal for Venice,” the most important scientific study ever conducted on the effects of navigation along Venice’s main port artery, the Malamocco Marghera Channel.
Two years between preparatory studies analysis and testing, with the construction of dedicated hydrodynamic models and navigation simulations, allowed to reconstruct and evaluate the effects of the operation of Venetian port traffic on the lagoon ecosystem, identifying possible actions that would allow to increase navigation safety, infrastructure operation and environmental sustainability.
The Authority, in order to have a study of unquestionable scientific value, relied, through a European public tender, on some of the most important international consulting firms in the sector – Force Technology, HS Marine, Cetena, Around Water – which acted with the coordination of DHI – Danish Hydraulic Institute, a true authority in the field of hydraulic and environmental research.
The study activities of the “Channeling the Green Deal for Venice” project were funded by the CEF (Connecting Europe Facility) Program to address the critical issues related to the limited nautical accessibility of the port of Venice, while respecting the environmental context of the Venice Lagoon, a UNESCO-protected site.
The study focuses in particular on the physical process that has the greatest impact on the evolutionary trends of the lagoon shallows adjacent to the canal, namely the displacement waves generated by the passage of ships, the effects of which are directly related to the relationship between the width of the canal section, the shape and size of the submerged portion of the ships’ hulls, and the speed at which the ships sail.
On the basis of the results obtained, the study team identified a number of design solutions, which have been validated with subsequent tests, and which would increase channel operation by up to three times in a safer situation, reduce maintenance costs, and limit erosion and sediment suspension phenomena by 50 percent.
Reducing the speed of ships is, first of all, mentioned as a primary goal to be achieved. For example, by reducing the speed from 10 to 8 knots, without affecting the safe “steerability” of the ship, a drastic reduction in the phenomenon of “draw down,” i.e., the rapid and significant lowering of the sea level as the ship passes, potentially related to erosive phenomena of the seabed, has been observed. This measure has already been implemented in a regulation of the Maritime Authority.
The Malamocco Marghera channel, which today has a base, or wedge, of 60 m with widenings up to 100 m and banks with a slope of 1:3, should be brought to the depth envisaged by the Port Master Plan, i.e. -12 m.
There are, in addition, some critical safety issues that would be overcome by rectifying the channel at some points, again within the perimeter of the Port Master Plan, such as at the San Leonardo bend and in the section near the Fusina terminal, to improve the safety of ships entering and leaving the docks, and beyond Fusina and towards Marghera.
The protection of the eastern bank of the channel through the creation of morphological structures similar to natural salt marshes, which could be created with the use of the excavated sediments, would significantly reduce wave propagation in the lagoon.
A total excavation volume of about 1.9 million cubic meters of sediment is expected for the proposed interventions. Excavation of about 2.5 million cubic meters would be required to build the morphological structures. The interventions would amount to about 42 million euros for the dredging component and 58 million euros for the reconstruction of the morphological structures.
“Sustainable growth of the port is already possible in the balance between development of economic activities and protection of the Lagoon,” – says Fulvio Lino Di Blasio, president of the North Adriatic Sea Port Authority. “This is demonstrated by the results of high scientific value produced by the study “Channeling the Green Deal for Venice,” which is based on 24 months of collaboration of the Authority, joined by the Harbour Master, Pilots and Tugs, with some of the world’s leading experts in hydraulic works, coordinated by the Danish Hydraulic System.” “The indications proposed by the research team, which focus on the need to reduce the speed of the ship and the implementation of minimal infrastructural changes along the Malamocco Marghera channel, would allow to triple the operability of the main access route to the port of Venice, improve safety and reduce by 50 percent the phenomena of seabed erosion and sediment suspension caused by the passage of ships.”
The scientific method
The study, which uses a recursive method, moves from an initial phase of characterization and hydrodynamic study of the examined environment. Downstream of a complex and articulated data acquisition and interpretation phase, a 2D model extended to the entire Venice lagoon area was prepared, with the aim of simulating, for a representative year, the spatiotemporal distribution of levels, currents, and the main wave motion parameters. This phase of work also included an activity of acquisition and interpretation of the sedimentological characteristics of the Venice lagoon, the factors influencing the erosion of shallow areas and the “critical” values of tangential stress at the bottom (bed shear stress), i.e., the values exceeded which trigger the suspension of the material constituting the bottom and, consequently, the erosive process. Subsequently, navigability modeling was carried out, with a 3D simulator of the transit of ships of various types and sizes under various weather and sea conditions, usefuli in particular to predict human behavior especially in adverse weather situations.
In the second phase of the study, technicians from the Authority, the Harbor Master’s Office, the Venice Pilot Corps, and the Tugboats were engaged for weeks in navigation simulation sessions at Force Technology’s headquarters in Denmark. The results of this phase, together with work on hydrodynamic and simulation models of displacement waves and Kelvin waves (the secondary waves) generated by the passage of ships along the channel, allowed the potential stress effects on the seabed to be assessed.
In the third phase, design solutions were put forward aimed at making the port’s operations more efficient, improving navigational safety, and containing environmental impacts from the passage of ships, including the creation of new protective sandbanks.
