CLASSIFICATION, DISTRIBUTION AND RETURN PERIODS OF COASTAL STORMS IN SW SPANISH LITTORAL: FIRST STEP IN A REGIONAL-SCALE VULNERABILITY ASSESSMENTNelson Rangel-Buitrago The occurrence of coastal storms constitutes the principal geohazard in different parts of the world. When the storms occur in urbanized areas, changes in beach morphology are accompanied by damages, important economic losses and sometimes deaths. Classification schemes for meteorological and climatic phenomena (i.e storms) provide beneficial information that is useful in evaluating their impacts on socio-economic activities and natural habitats. In this sense, this work assesses classification, distribution and return periods of coastal storms in SW Spanish littoral, as a first step in a regional scale vulnerability assessment. For this purpose, wave data were obtained from five points (Huelva, Chipiona, Cadiz, Conil and Bolonia) of the HIPOCAS network. The total wave power index was used to classify coastal storms into five classes, from weak to extreme. In a further step, the generalized extreme value distribution (GEV) has been applied to estimates return periods. The wave power index was calculated according to the formulation Hs2td, with Hs being the significant wave height and td the storm duration in hours. Concerning the obtained results, important differences in the number and approaching directions of storms can be highlighted. Huelva and Chipiona locations respectively recorded 137 and 189 storms approaching from the third quadrant, Cadiz and Conil respectively recorded 377 and 369 storms approaching from the third and fourth quadrants, with very few events approaching from the second quadrant. Bolonia location recorded most elevated number of storms (422), they approached principally from the third quadrant (303 events) and secondarily from the second and forth quadrants, respectively with 59 and 60 events. The distribution of storm classes was very similar at all locations. Classes I (weak) and II (moderate) respectively accounted for 60% and 23% of events included in the data set. Class III (significant), recorded 10% of the events and Classes IV (severe) and V (extreme) accounted for 5% and 2%, respectively. Maximum values of storm power presented a cyclic behavior more than a defined trend. Return period for Class V events ranged from 2 to 12 yrs, with average values of 7-8 years and values from 1 to 3 yrs were observed for Classes I to IV. The information previously presented should be relevant to assess the vulnerability and risk of coastal systems in the SW Spanish littoral to storm impacts. This provides to the decision-makers information about their potential consequences to apply mitigation and/or adaptation strategies in this coastal zone. |
