Fig 1.
The white dashed line marks the pattern of the Malamocco˗Marghera channel (MMC), the waterway connecting Malamocco inlet with the Porto Marghera Industrial Zone (PMIZ). The insets in the map show the location of the study area Cassa di Colmata B, CC-B) and the bathymetric profile of the navigation channel in the investigated sector. Data source: open database CIGNO [39].
Fig 2.
Bathymetric map of the Lagoon of Venice.
Colour-shaded bathymetric map of the Lagoon of Venice. The dashed black line identifies the central lagoon area affected by significant erosion and flattening of the morphology, as described in [47]. Data source: open database CIGNO [39].
Fig 3.
Map of the investigated shoreline.
The 15 control sections investigated in the field survey (short term) and in GIS-based analysis (long term) are indicated. Red dots: the location of sampling points for grain-size analysis. Yellow symbols: the location of probe (cross) and pressure sensor (square). Image source: WMS service of The Italian National Geoportal 2012 [48].
Fig 4.
A depression wake originated from the cargo ship Abu Dhabi Star on 1St April 2014 at 03.30 PM in transit along the MMC as measured on the channel side at 70 m (top panel), and over the CC-B shore, at about 190 m (bottom panel) from the channel center.
Fig 5.
Aerial view of a cruise ship transit in the MMC.
The depression wake exposes the collapsed materials of the original rip-rap revetment of the embankment at the southern end of the Cassa di Colmata B (CC-B). Image source: author’s picture.
Fig 6.
Typologies of stratigraphic sequences in the CC-B.
A) northern section, bauxite deposits at the bottom, overlaid by sandy sediments from dredging; B) central section, the bottom is a composite layer, mostly sandy sediments, with lenses of shells and shell fragments overlaid by a silty-sand layer hosting clods of mud deriving from dredging; C) southern section, the bottom layer is a natural sandy sediments from fluvial deposition (former Brenta River) overlaid by dredged mud with a large amount of mud clods.
Fig 7.
Sediment grain size distribution.
Samples collected on the main erosional scarp of the CC-B. T = top of the scarp; B = bottom of the scarp. The numbers correspond to the fifteen control sections investigated in the field survey. Image source: WMS service of the Italian National Geoportal 2012 [39].
Fig 8.
Cumulative retreat of the CC-B shoreline from April 2014 and January 2015.
The fourteen sections have been clustered in the three main groups. Average trend for each group is shown together with the range of variation (grey lines).
Fig 9.
Long-term evolution of the study area.
The outline of the original extension of CC-B is shaded in the three images (A, B, and C); the lower right enlargement (D) shows the system as it appeared in 2012 and the evolution of the shoreline from 1974 to 2015. The MMC margins are marked with white lines. Image source: (A) open database CIGNO [39]; (B) Veneto Region geoportal [50]; (C and enlargement D) WMS service of the Italian National geoportal [48].
Fig 10.
Cumulative change in CC-B shoreline position in the period 1974–2015.
Data are calculated from the shoreline of 1974. The variations of the shoreline were obtained by detailed GIS-based analysis of the fifteen control sections. Grey lines indicate the range of variation.
Fig 11.
Changes in the elevation of CC-B reclaimed area.
The differences in elevation were obtained from 1968 and 2015 DTM. Inset: enlargement of the northern part of the studied area, where the maximum erosion was estimated. Background image source: WMS service of the Italian National Geoportal 2012 [48].
Fig 12.
Annual distribution of high tides ≥1.1 m recorded in Venice from 1872 to 2015 (A). The inset shows the distribution of tides > 0.8 m in the period April 2014-January 2015. (B). Data courtesy Istituzione Centro Previsione e Segnalazione Maree of the Municipality of Venice [55].