Links between hydrology and sedimentology in the Lagoon of Venice, Italy

Abstract

A textural classification of sediments collected in input channels, shallow lagoon beds and navigation channels of the Lagoon of Venice is presented. Some variables describing both the hydrodynamics and the transport time scales of the Lagoon are compared with bottom sediment distribution inside the basin. A high correlation between residence time (REST) and the silt fraction (4-31 µm) was only found for REST values < 20 days. A good correlation was also found between root mean square velocity (RMSV) and the fine sand fraction (63-105 µm) for RSMV > 10 cms -1 . The distribution of the various sediment types was explained by the use of PCA applied to both grain-size and hydrological parameters, which extracted two principal factors and formed four groups of clustered samples. Groups 1 (clayey silt) and 2 (very silty slightly sandy mud) comprise samples located mainly in the northern and central lagoon and inshore. The samples of group 3 (very silty sandy mud) seem to show stabilisation, reflected in the reduction of sand and the sedimentation of silt with respect to samples in group 4 (slightly silty sand), some of which were collected on a previous seagrass bed which has now disappeared and/or been reduced in size.

Thirty-year changes (1970 to 2000) in bathymetry and sediment texture recorded in the Lagoon of Venice sub-basins, Italy

“…The results confirm a previous study (Molinaroli et al, 2007) in which LV sediments sampled in the period 1997-98 were found to be more similar to back-barrier tidal flats (Danish Wadden Sea) and bays (Minas Basin, Bay of Fundy, Canada) than lagoon sediments (Mugu Lagoon, California).…”

“…In this part of the LV tidal currents and bed shear stress due to wind waves and fetch length increased between 1970 and 2000, mainly in the B and C sub-basins and are the causal explanation of changes in bathymetry (Amos et al, 2004;Umgiesser et al, 2004b;Molinaroli et al, 2007).…”

“…The lagoon varies from relatively high energy on the seaward side, influenced by tidal flow through the three inlets connecting the lagoon to the Adriatic, to quiescent conditions on the landward side (Umgiesser et al, 2004b;Molinaroli et al, 2007).…”

“…Most of these studies lack a detailed description of the spatial distribution and transport mechanisms of the sediments affected by changes in bathymetry, although the general textural trends in the LV are well-known (Basu and Molinaroli,1994;Albani and Serandrei-Barbero, 2001;Molinaroli et al,2007). For example, despite the importance of accretional and erosional trends in estimating particle size/transport processes in lagoonal basins, no references or estimates for the LV ecosystem are available in the literature on bathymetry and grain-size.…”

Assessing hydrological effects of human interventions on coastal systems: numerical applications to the Venice Lagoon

“…Only in few cases, i.e. Aveiro Lagoon (Duck and da Silva, 2012), Venice Lagoon (Molinaroli et al, 2007;Sarretta et al, 2010) and San Pablo Bay (Jaffe et al, Published by Copernicus Publications on behalf of the European Geosciences Union.…”