Run-up computation behind emerged breakwaters for marine storm risk assessment

Flood vulnerability assessment due to marine storms is very important for integrated coastal zone management. The case study site is a highly developed area (Rimini) along the Emilia Romagna coastline, facing the north Adriatic sea in Italy. This area is composed of low sandy beaches and is completely protected by emerged breakwaters. Rimini was chosen in order to assess the vulnerability of a very important tourist resort that represents one of the most significant revenue for the regional economy. For the vulnerability assessment it was decided to consider the worst scenarios, using a joint probability of occurrence for a 1, 10 and 100 years return period storm, happening at the same time as an atmospheric surge and with the maximum spring tidal level of +0.45 m above MSL (run-up + surge + tide). The beach slope of different profiles was calculated using the a 2004-DTM (Lidar-based). The attenuation effect of the breakwaters was considered inside the run-up formula using the following method: (i) a 1-d model was used to evaluate the wave height at the seaward foot of each structure; (ii) the Van der Meer formula was applied to calculate the wave height behind structures; (iii) the calculated wave height was transported back to deep water conditions using a 1-d model. Different damage categories were created. The results reveal that, even with the one year event, most of the infrastructures are damaged and the areas behind the beach are flooded