Saving Venice by seawater

Abstract

[1] The frequency of flooding in Venice has drastically increased over the last 50 years as a major consequence of natural and anthropogenic land subsidence, mean sea level rise, and a more active lagoon hydrodynamics induced partly by deepening of the largest navigation channels. Subsurface fluid injection is a well-established technology that is currently used either to enhance oil recovery from oil fields or to reduce land settlement due to hydrocarbon production. To help mitigate the inundation events in Venice, a numerical study of seawater injection into a 600-800 m deep geologic formation is performed with the aid of advanced numerical fluid dynamic and geomechanical models. A number of parametric scenarios are addressed, consistent with the basic geological configuration derived from the lithostratigraphy of nearby areas in the northern Adriatic basin. Preliminary quite encouraging results show that a set of 12 vertical injection wells, strategically located within the lagoon, may raise Venice from 11 to up to 40 cm over a 10 year period, thus offsetting or mitigating the vast majority of the high tides that occasionally plague the city. Further ad hoc geological and geophysical investigations of the lagoon subsurface are required before the present prefeasibility study can be turned into a design project of anthropogenic Venice uplift.

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“…In an interview released by Courier-Mail World News, an Australian newspaper, a few days later [Falconi, 2005], Jamiolkowski updated his estimate and suggested that 15 centimeters of anthropogenic uplift could be possible. Although this is a smaller amount than that predicted by Comerlati et al [2003Comerlati et al [ , 2004, it is 3 times Jamiolkowski's original estimate, and a 15-centimeter heave would be of great practical interest for Venice.…”

“…In contrast, Jamiolkowski, also one of the chief consultants to CVN (the consortium of enterprises mandated by the Italian government to fund all the investigations and interventions fi nalized to protect Venice from the acqua alta, including the design and construction of MOSE), concluded that any in situ experimentation is premature, and he argued that the injection project would yield an uplift of only a few centimeters. On the basis of his own experience with shallow soils, Jamiolkowski assumed, without any fi eld evidence, an injected formation 5 times stiffer than the one addressed by Comerlati et al [2003Comerlati et al [ , 2004, thus implying a proportionally reduced uplift (5-6 centimeters). Comerlati et al [2003Comerlati et al [ , 2004 used data derived from actual measurements of deep in situ rock compaction and expansion performed with the aid of the marker technique [Baú et al, 2002], a consolidated approach implemented in the petroleum fi eld by major service companies such as Schlumberger and Western Atlas.…”

“…On the basis of his own experience with shallow soils, Jamiolkowski assumed, without any fi eld evidence, an injected formation 5 times stiffer than the one addressed by Comerlati et al [2003Comerlati et al [ , 2004, thus implying a proportionally reduced uplift (5-6 centimeters). Comerlati et al [2003Comerlati et al [ , 2004 used data derived from actual measurements of deep in situ rock compaction and expansion performed with the aid of the marker technique [Baú et al, 2002], a consolidated approach implemented in the petroleum fi eld by major service companies such as Schlumberger and Western Atlas.…”

Injection of solids to lift coastal areas

“…Numerical simulations of the injection process (Comerlati et al 2004) suggest that the pore pressure would increase by approximately Dp = 1.2 MPa in 10 years. Values cited above indicate an expected displacement of 24 cm, according to equation (1.1), consistent with the uplift of 10-40 cm resulting from detailed finite-element analyses (Comerlati et al 2004). Therefore, the total displacement achieved using the poroelastic effect is probably limited to fractions of a metre for reasonable combinations of variables in equation (1.1).…”

“…Another approach to raising Venice is based on the poroelastic effect produced by the subsurface injection of sea water (Comerlati et al 2004;Castelletto et al 2008). Vertical displacement resulting from an increase in pore pressure Dp is approximately…”