Probabilistic coastal vulnerability assessment to storms at regional scale: Application to the coast at North-East Aegean Sea (Thrakiko Pelagos), Greece

In this study, a probabilistic vulnerability assessment to the impact of storms in the coast of Thrace, Greece was carried out. To this end, the methodology presented by Bosom and Jiménez (2011) has been applied with some modifications. The introduced modifications, for this work, were the use of a different run-up model to deal with the uncertainty in the predicted magnitude (due to some reported under-prediction of run-up, using Stockdon et al. equation, 2006) observed in recent studies (Laudier et al. 2011). In addition, the vulnerability framework has been extended by including overtopping in order to characterize better the flooding hazard. For this project, the study area was the coast of Thrace, Greece and the used data were 3-h hindcasts of the WAM model for a time period of 10 years (January of 1995 – December of 2004) at fifteen stations of the N. Aegean Sea. Its variables were the significant wave height, Hs, the wave peak period Tp, the wave direction, Hdir. With this dataset, the return values of the hazards’ (i.e. inundation and erosion) for the return periods of 5, 10, 30 and 50 years were estimated, using the Reis and Stockdon equation to calculate the wave-induced run-up and the numerical model SBEACH to calculate the storm-induced erosion. Aim of these estimations was to compare the difference between each hazard magnitude with the corresponding geomorphologic parameter (i.e. beach height and width, respectively) in order to characterize the vulnerability of the coast against each hazard and for each return period. The obtained results along the coast reflect the relative variation of the hazard magnitude in function of the beach morphology, which is mild-sloped and low beaches presenting the largest values for inundation, while the steeper and narrower ones are the most sensitive to erosion. Finally, an integrated vulnerability assessment was presented and some possible recommendations to mitigate the problems were given. It must be stressed that coastal managers play an important role in the final assessment, since they must decide the probability of occurrence to be accepted as well as the period of concern of the analysis. These two variables will determine the return period to be considered for the decision-making.Coastal EngineeringHydraulic EngineeringCivil Engineering and Geoscience