Recent evolution of the Tiber River delta and future scenarios of coastal vulnerability

Many studies that integrate morphological, stratigraphic, sedimentological and geoarchaeological data, allowed the reconstruction of the Tiber River delta evolution during the Late Pleistocene-Holocene. The post-glacial sea level rise was the main controlling factor of delta changes until ca. 6 ka BP. Afterwards, when the modern sealevel highstand was attained, autocyclic processes prevailed during the last 5-6 ka while in the last 2 ka man activity became more and more important. We used detailed reconstructions of the past history, that reflects hydrodynamic and geomorphologic changes affecting the coastal dynamics, to delineate future scenarios and address predictive searches for the near-future, according to SLR projections and estimated sediment input. These results along with new data, deriving from the ongoing SECOA (Solutions for Environmental contrasts in Coastal Areas) European Project, allowed the evaluation of the coastal vulnerability index (CVI) relevant to storm waves in the area of the Tiber delta (from Fiumicino to Castelporziano). The variables; used to define the CVI assessment are of two different types: the “morphometric” variables, ranked on the basis of present-day measurement (i.e. beach mean elevation) and the “morphodynamic” variable, parameterized according to their changes in time (i.e. changes in the upper shoreface slope). Among the morphometric variables we also included anthropic structures that decrease the natural vulnerability. The CVI was calculated by using a multiple regression equation, in which each variable is scaled by an efficacy coefficient. The methodology was applied both to the short-term and long-term interval (up to 2100). With reference to the latter, we considered the impact of relative sea level rise according to the IPCC (4R, 2007) and Rahmstorf hypotheses (2007).