A new 3-D non-linear model of the subsidence of Venice
P. Teatini, G. Gambolati
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
L. Tosi
Istituto per lo Studio della Dinamica delle Grandi Masse, CNR, Venezia,
Italy
ABSTRACT
A new quasi 3-D nonlinear finite element model is developed for the simulation and
prediction of land subsidence due to groundwater withdrawal in the Venice Lagoon.
The nonlinearity is accounted for by the use of aquitard hydraulic conductivity
and specific elastic storage related to the effective intergranular stress
and solved by a block successice over-relaxation (SOR) procedure with the optimal
block SOR factor. The hydrologic response is then fed into a nonlinear 1-D
vertical compaction model. The overall modelling approach is applied to the regional
multiaquifer system underlying the Venetian Lagoon where extensive groundwater pumping
from the upper aquifers has caused an alarming land subsidence at Venice over the
period 1950-1970 and a more modest settlement in the southern and northern lagoon
areas thereafter. The 3-D nonlinear flow and the 1-D compaction models have been
calibrated against the past available piezometric and settlement records and
reproduce very satisfactorily the event as was observed from the inception of
pumping until the early seventy when the cone of depression achived the largest
extent. The simulations for later years up to the present time are currently
under way.
