Figure 118: Flooding at + 8 cm above sea level (light blue) and at + 10 cm (dark blue.)
Venice is a city of dramatic variability of environmental conditions, both tidal and topographical. The architecture of Venice has developed in response to these environmental contingencies. Piles allow construction on earth with low bearing capacity, as do lighter Venetian bricks, 2 inches thinner than Roman brick, and special Venetian techniques of light roof construction. The traditional Venetian house is composed of two or three bays, the narrow width of these bays limited to a few standard dimensions by the low carrying capacity of the sandy or silty soil beneath. Light brick walls were protected from moisture erosion with a facing of marble reaching just above the highest expected tide level at time of construction.
Figures 108-110: Typical wall sections of canal and residence. In blue, the highest expected water level at time of construction as evidenced by the height of the marble facing.
Figure 105: 18th century design proposal for Venetian abbatoir, note highly specific program and soil contingent arrangement of foundation piles.
Figures 111-114: Ca’ d’Oro: a typical 2 bay residence. Facade; plan of ground floor and levels 1 and 2.
Figure 107: Ca’ d’Oro: section showing thin, closely spaced floor beams typical of traditional Venetian residential construction.
Figure 106, 107: Typical Venetian residential roof construction, note thin purlins and plaster cieling to reduce weight of structure.
Figure 103: Map of Venice, 1346. Settlement of Venice began on areas of soil of high bearing capacity. Architecture built at this time utilized conventional foundations. By the end of the 14th century, settlement advanced over soils with poor bearing capacity, and from this time on, pile or raft foundations were utilized.
Figure 104: Soil types, Venice lagoon
The existing architecture of Venice has reached a limit condition wherein strategies utilized to manage environmental variability can no longer effectively accomodate the increasing rate of change brought on by global warming. Lagoon water now routinely rises above the marble facing protecting building and canal walls, causing bricks to erode. Piazza San Marco has been repaved, stacking layer upon layer, as sea levels rise, but now paving has been installed at a level where it has begun to interfere with the thresholds of Saint Mark's. The paving cannot be raised again, yet the piazza is flooded an ever increasing number of days each year.
Figure 120: Erosion and sedimentation patterns in Venice lagoon. Erosion is occuring at an ever increasing rate each year.
Figure 119: Remaining stands of sea grass, Venice lagoon. Poisioning of sea grass by industrial pollutants has increased the rate of erosion.
Top left to bottom right: Flooding pattern at current sea level, at +1 M, +2 M, and +3M. Greater Venice is located on an enormous flood plane which could become entirely submerged if the polar icecaps continue to melt.
Figure 122: MOSES flood gate. The MOSES rests at the bottom of the ocean near the lagoon inlet and is raised pneumatically during high tides. It is estimated that within 25 years, it will be raised so many days per year that it will interfere with the natural tidal flushing of the lagoon, allowing a dangerous level of bacteria and pollutants to concentrate in the canals.
Figure 121: Current velocity at lagoon inlet. The reconfiguring of the inlets of the Venice lagoon have increased the current velocity, thus increasing rates of erosion.
Figures 115-117: Flooding in Venice