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CENAS Project

REGIONAL SUBSIDENCE MODEL


We have simulated the evolution of the accreting column at three strategic locations (Venice, Po river delta, Ravenna) along the Northern Adriatic coastline. The geological time covered by the numerical simulation includes the Middle-Upper Pleistocene, the Holocene and the historical are. The prediction is projected until the end of the next century.

Ingression of the Adriatic Sea into the Po river plain around 1 My before present

Maximal extension of the Po river plain during the Wurm glaciation, 20000 years before present

The analysis is performed by a 1-D nonlinear finite element model of soil compaction driven by groundwater flow in an isothermal sedimentary basin subject to a continuous vertical sedimentation process.

Consistent with the available information, the model is run so as to reproduce the present day sediment thickness and a negligible pore pressure in excess of the hydrostatic value along the compacting column. The calibrated uniform vertical permeability Kz assumes the values: 10-10 m/s at PORTO GARIBALDI 2, 6*10-11 m/s at FIUMI UNITI 1, 5*10-10 m/s at GORO 1, and 6*10-11 m/s at LIDO 1.

Length of the accreting column and column compaction versus geological time

Pore pressure in excess of the hydrostatic value along the column length in 2100 AD

Pore pressure in excess of the hydrostatic value versus geological time at the bottom of the accreting column

We have assumed that subsidence is in equilibrium with sedimentation during the time intervals with zero variation of the bathymetry. By distinction, a decrease of the sea depth requires a correspondingly equal increase of the accreting column length

Behavior of column top, bottom and length versus geological time

Behavior of the raising velocity of the column top, settling velocity of the column bottom and depositional rate versus geological time at PORTO GARIBALDI 2

Behavior of the raising velocity of the column top, settling velocity of the column bottom and depositional rate versus geological time at FIUMI UNITI 1

Behavior of the raising velocity of the column top, settling velocity of the column bottom and depositional rate versus geological time at GORO 1

Behavior of the raising velocity of the column top, settling velocity of the column bottom and depositional rate versus geological time at LIDO 1

The predictions obtained from the model are consistent with recent observations of natural land settlement and indicate for the next 100 years expected rates of land subsidence equal to 0.5 mm/y in the Venice lagoon, 2.5 mm/y in the Ravenna area, and 5 mm/y in the Po river delta.

Behavior of the settling velocity of the column bottom and of the column top from 1700 to 2100 AD


Presentation author: Andrea Pellizzon