Assessment of the impacts of storm events for developing an erosion index

During a storm event, strong winds combined with low atmospheric pressure and high water level conditions generate surge which often cause significant beach erosion. Over the years, a number of storm erosion indexes have been developed combining marine factors, but none of them incorporate wind and large-scale atmospheric factors of the storm events. The occurrence of wind storms was examined along the Belgian coast within a time span of 14 years (1994-2007) with respect to the local marine and large-scale atmospheric factors (circulation weather types, CWT and the winter North Atlantic Oscillation, NAO) under which the events took place. It was shown that 181 wind storms were recorded (average of 14 events per year). This was characterized by a calm period with a range of annual events from 6 to 14 between 1994 and 2001, following by an energetic period of frequent events reaching up to 18 events per year for the most recent years. However, only 8% of the wind storms were related to the measured erosion events. Based on the assessment of the wind storm characteristics, the events were filtered with respect to the high water level, and the occurrence of primary and secondary CWTs in order to identify the potential erosive wind storm events. Results indicated that more than 63% of the wind storms were related to the measured sand volume loss of the beaches. Also, it found that the occurrence of severe wind storms is regulated by the winter NAO index. Based on these considerations, an index for the intensity of the wind storm activity is built to model the induced erosion volume. A reliable and robust erosion model can help to better prepare coastal managers and coastal communities for preventing the morphological impacts of severe storms in the future.