What Happens to a Mediterranean Microtidal Wave-dominated Beach during Significant Storm Events? the Morphological Response of a Natural Sardinian Beach (Western Mediterranean)

The short-term effects of storm events on the coastline morphology of natural, microtidal, wave dominated beaches located in the western Mediterranean are still poorly documented. Since one of the most visible consequences of a warming climate is an increase in the intensity and frequency of extreme weather conditions, it appears important to know the response of natural and urban beaches to these storm events. The spatial shoreline variability of a natural Sardinian beach was assessed in our study, based on video camera monitoring data from August 2013 to August 2015 along a 0.3 km stretch of sandy beach. This methodology has been applied in the SW coastal sector of Sardinia where severe storm events mainly related to southwesterly winds (about 50 km/h on average) can induce important morphological changes. These include shoreline retreat/progradation, erosion, beach rotation, reconfiguration of nearshore bars and the deposition of significant seagrass beach-cast litters. Our study showed an erosion and a consequent accretion of the studied beach of about 20 m in two days after the event (SW wind and waves) as a result of the deposition of the Posidonia oceanica beach-cast litter. This morphological response induced by storm events is crucial for coastal managers to plan beach management (for example beach cleaning practice), to prevent coastal risk and to understand the importance of seagrass berm deposition in the formation of natural Mediterranean beaches.