234 13 th International Conference on Protection and Restoration of the Environment Editors: A. Kungolos, C. Christodoulatos, A. Koutsospyros, C. Emmanouil, C. Laspidou, Z. Mallios, D. Dermatas ISBN: 978-960-6865-94-7 Assessing coastal zone response under extreme storm events for flood risk management. The case study of Rethymno, Greece E. V. Kragiopoulou 1 , Ε. S. Skarlatou 1 , A. Lykou 2 , C. Makropoulos 2 , V. K. Tsoukala 1* 1 Laboratory of Harbour Works,Department of Water Resources and Environmental Engineering, School of Civil Engineering, National Technical University of Athens, Iroon Polytechniou 5, 15780 Athens, Greece. 2 Hydrology and Water Resources Utilization Laboratory, Department of Water Resources and Environmental Engineering, School of Civil Engineering, National Technical University of Athens, Iroon Polytechniou 5, 15780 Athens, Greece. *Corresponding author: Email: tsoukala@mail.ntua.gr Abstract Flooding has always been a serious problem for Rethymno, Greece as major flood events have been encountered throughout the years resulting in serious damages. For this reason, Rethymno city is one of the case study areas of PEARL project, an EU-funded research project, which aims to develop and apply adaptive risk management strategies for coastal communities against extreme hydro-meteorological events, minimizing social, economic and environmental impacts. Within this framework, estimating wave overtopping, wave run-up and coastal erosion in Rethymno is of great importance as consequences of coastal flood events arising from storms and storm surges, sea level rise and tsunami. In this study, XBeach numerical model is applied on the coastal zone of Rethymno in order to assess the coastal response to time-varying extreme storm events. The output obtained refers to hydrodynamics, sediment transport, bed update and wave run-up calculations, enabling the stakeholders to identify the most vulnerable areas. Keywords: extreme storm events; flood management; hydrodynamics; sediment transport; wave run-up; XBeach; Rethymno 1. INTRODUCTION Coastal floods are regarded as one of the most dangerous and harmful of all natural disasters. Climate change combined with rapid urbanization and poor governance lead to a significant increase in the exposure of people, livelihoods, environmental services, resources and infrastructure of coastal communities to hazard. Flooding has always been a serious problem for Rethymno, Crete, Greece. Major flood events have been encountered throughout the years, resulting in serious damages mainly in the Old Town of Rethymno and the east low-laying areas [1]. For this reason Rethymno city (Figure 1a) is one of the eleven case study areas of PEARL (Preparing for Extreme And Rare events in coastal regions) project, an EU funded research project, which aims at developing adaptive risk management strategies for coastal communities focusing on extreme hydro-meteorological events, with a multidisciplinary approach integrating social, environmental and technical research and innovation so as to increase the resilience of Coastal Regions all over the world. Within this framework, the XBeach public-domain numerical model is used in this project. XBeach is a two-dimensional morphological model for wave propagation, long waves and mean flow, sediment transport and morphological changes of the near-shore area, beaches, dunes and backbarrier during storms [2].