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## CENAS Project## SURFACE SUBSIDENCE MODEL |

After the Second World War the Romagna coastal stretch between the Po river delta and Cattolica has experienced a dramatic land settlement mainly due to the water withdrawal which has characterized the economic and tourist development of this area since the early 50's.

The transient 3-D finite difference hydrologic model MIKE SHE and a 1-D finite difference consolidation model have been calibrated and used to simulate land subsidence due to groundwater withdrawal from 1950 to present, and to predict the expected land settlement until 2100.

Map of the study area where the hydrologic cycle of the multiaquifer system is simulated

Two evolution scenarios are considered for the future pumping trend. The first `optimistic' scenario assumes that the present pumping will be decreased by 10% before 2015. The second `pessimistic' scenario assumes an increase of 10% of the water demand before 2015. No realistic assumptions can be made for water demand lated than 2015. A theoretical exercise is performed by assuming that the drawdown varies parabolically from the 2015 rate to zero in 2050, and then the piezometric head remains stable from 2050 to 2100.

The outcome of the hydrologic model is used as boundary condition for the subsidence model, which is applied at a few locations of interest where some stratigraphic data are available.

Location of the sites where land subsidence is simulated