Coastal storm characterization and morphological impacts on sandy coasts

The present work deals with storm classification, using the Storm Power Index, and beach morphological response to storm events in the Gulf of Cadiz (SW Spain). Over the 1958-2001 period, 377 events divided into five classes ranging from weak to extreme were characterized. Classes I (weak) and II (moderate) accounted for 60% and 23% of events, respectively. Class III (significant), were 9% of the recorded events and Classes IV (severe) and V (extreme) accounted for 5% and 2%, respectively. The probability of storm occurrence per year ranged from 93% for Class I to 15% for Class V. In order to characterize beach response to storm events, 214 beach profiles carried out with a monthly periodicity over the 19961998 period along the Chipiona-Rota littoral were analysed, as well as published data. Different beach types were observed: (i) Intermediate beaches underwent important vertical relief changes ranging from 0.3 m to 1.33 m associated with average slope changes from tan beta=0.06 to tan beta=0.03; (ii) the dissipative beaches were characterized by smaller and homogeneous foreshore vertical changes, from c. 0.36 m to 0.65m, according to the parallel retreat mechanism characterized by small slope variations (from tan beta=0.025 to tan beta=0.035); and (iii) intermediate with rock shore platform experienced small morphological and foreshore slope variations, related to both beach pivoting and parallel retreat mechanisms. The most important morphological changes were due to the impact of usually weak and moderate events during October and November that produced berm erosion and upper foreshore lowering, and the impact of severe, significant and extreme events in December and January which produced dune escarpment, overwash and/or damage to coastal structures. Copyright (C) 2011 John Wiley & Sons, Ltd.