Global change and relative sea level rise at Venice: what impact in term of flooding
- 2.7k Downloads
Relative sea level rise (RSLR) due to climate change and geodynamics represents the main threat for the survival of Venice, emerging today only 90 cm above the Northern Adriatic mean sea level (msl). The 25 cm RSLR occurred over the 20th century, consisting of about 12 cm of land subsidence and 13 cm of sea level rise, has increased the flood frequency by more than seven times with severe damages to the urban heritage. Reasonable forecasts of the RSLR expected to the century end must be investigated to assess the suitability of the Mo.S.E. project planned for the city safeguarding, i.e., the closure of the lagoon inlets by mobile barriers. Here we consider three RSLR scenarios as resulting from the past sea level rise recorded in the Northern Adriatic Sea, the IPCC mid-range A1B scenario, and the expected land subsidence. Available sea level measurements show that more than 5 decades are required to compute a meaningful eustatic trend, due to pseudo-cyclic 7–8 year long fluctuations. The period from 1890 to 2007 is characterized by an average rate of 0.12 ± 0.01 cm/year. We demonstrate that linear regression is the most suitable model to represent the eustatic process over these 117 year. Concerning subsidence, at present Venice is sinking due to natural causes at 0.05 cm/year. The RSLR is expected to range between 17 and 53 cm by 2100, and its repercussions in terms of flooding frequency are associated here to each scenario. In particular, the frequency of tides higher than 110 cm, i.e., the value above which the gates would close the lagoon to the sea, will increase from the nowadays 4 times per year to a range between 20 and 250. These projections provide a large spread of possible conditions concerning the survival of Venice, from a moderate nuisance to an intolerable aggression. Hence, complementary solutions to Mo.S.E. may well be investigated.
KeywordsEustatic rise Northern Adriatic Geodynamics Venice Flooding
Part of the study was supported by the CNR “curiosity driven” Project DG.RSTL.080.027 and the INLET Project supported by the Venice Water Authority. ERS and ENVISAT SAR data have been processed by GAMMA Remote Sensing Research and Consulting AG (Switzerland).
- Brambati A, Carbognin L, Quaia T, Teatini P, Tosi L (2003) The Lagoon of Venice: geological setting, evolution and land subsidence. Episodes 26:264–268Google Scholar
- Carbognin L, Taroni G (1996) Eustasy at Venice and Trieste in the last century (in Italian). Atti Istituto Veneto SSLLAA Classe di Scienze Fis Mat e Nat 154:33–52Google Scholar
- Carbognin L, Gatto P, Mozzi G, Gambolati G, Ricceri G (1977) New trend in the subsidence of Venice. In: Rodda JC (ed) Land subsidence. IAHS Publ no 121, Washington, DC, USA, pp 65–81Google Scholar
- Gentilomo M, Cecconi G (1997) Flood protection system designed for Venice. Hydropower Dams 2:46–52Google Scholar
- Harleman DRF (2002) Saving Venice from the sea. J Hydraul Res 40:81–85Google Scholar
- Intergovernmental Panel on Climate Change (IPCC) (2007) Climate change 2007: Synthesis Report. IPCC, Geneva, p 52Google Scholar
- Jeftic L, Keckes S and Pernetta JC (1996) Implications of future climatic changes for the Mediterranean coastal region. In Climate change and the Mediterranean, vol 2. Edward Arnold, London, pp 1–25Google Scholar
- Pirazzoli PA, Tomasin A (2008) Sea level and surges in the Adriatic Sea area. Atti Istituto Veneto SSLLAA Classe di Scienze Fis Mat e Nat 166:61–83Google Scholar
- Tosi L, Teatini P, Carbognin L, Brancolini G (2009) Using high resolution data to reveal depth-dependent mechanisms that drive land subsidence: the Venice coast, Italy, Tectonophysics. doi: 10.1016/j.tecto.2009.02.026