Hydrogeological effects of dredging navigable canals
through lagoon shallows. A case study in Venice
P. Teatini, S. Nardean, M. Ferronato, A. Mazzia
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
G. Isotton
M3E S.r.l., Padova, Italy
C. Da Lio, L. Zaggia, D. Bellafiore, L. Tosi
Institute of Marine Sciences, CNR, Venezia, Italy
M. Zecchin, L. Baradello
National Institute of Oceanography and Experimental Geophysics (OGS), Sgonico, Italy
F. Cellone
Centro de Investigaciones Geologicas, Consejo Nacional de Investigaciones Cientificas y Tecnicas,
La Plata, Argentina
F. Corami, A. Gambaro, E. Morabilto
Institute of the Dynamics for the Environmental Processes, CNR-IDPA, Mestre-Venice, Italy
G. Libralato
Department of Biology, University of Naples Federico II, Naples, Italy
A. Volpi Ghirardini
Department of Environmental Sciences, Informatics and Statistics, Ca' Foscari University of Venice,
Mestre-Venice, Italy
R. Broglia, S. Zaghi
Marine Technology Research Institute, CNR-INSEAN, Rome, Italy
For the first time a comprehensive investigation
has been carried out to quantify the possible effects of dredging
a navigable canal on the hydrogeological system underlying
a coastal lagoon. The study is focused on the Venice
Lagoon, Italy, where the port authority is planning to open a
new 10m deep and 3 km long canal to connect the city passenger
terminal to the central lagoon inlet, thus avoiding the
passage of large cruise ships through the historic center of
Venice. A modeling study has been developed to evaluate the
short (minutes), medium (months), and long (decades) term
processes of water and pollutant exchange between the shallow
aquifer system and the lagoon, possibly enhanced by the
canal excavation, and ship wakes. An in-depth characterization
of the lagoon subsurface along the channel has supported
the numerical modeling. Piezometer and sea level records,
geophysical acquisitions, laboratory analyses of groundwater
and sediment samples (chemical analyses and ecotoxicity
testing), and the outcome of 3-D hydrodynamic and computational
fluid dynamic (CFD) models have been used to set up
and calibrate the subsurface multi-model approach. The numerical
outcomes allow us to quantify the groundwater volume
and estimate the mass of anthropogenic contaminants
(As, Cd, Cu, Cr, Hg, Pb, Se) likely leaked from the nearby
industrial area over the past decades, and released into the
lagoon from the canal bed by the action of depression waves
generated by ships. Moreover, the model outcomes help to
understand the effect of the hydrogeological layering on the
propagation of the tidal fluctuation and salt concentration
into the shallow brackish aquifers underlying the lagoon bottom.
