Winter storm characterization and related impacts along Cadiz littoral

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Tuesday 30 june 2015

17:33 - 17:36h at North America (level 0)

Themes: (T) Extreme events, natural variability and climate change, (ST) Hydrological extremes: floods and droughts, Poster pitches

Parallel session: Poster pitches: 7I. Extreme - Flood Drought

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Climatic change-related impacts on coastal areas became an important issue in past decades and nowadays threatened many ecosystems. Coastal hazards are linked to flooding and erosion processes associated with sea level rise and the increased strength of hurricanes, cyclones and storms. The main aims of this work are: I) the characterization of coastal storms in Cadiz (SW Spain), II) the determination of their recurrence intervals and relationships with several regional cycles and III) the analysis of beach response to extreme erosive events recorded during the 2009-2010 winter season at Levante Beach (Cadiz, SW Spain). Storm characterization was carried out using the Storm Power Index (Dolan and Davis, 1992), and five classes were obtained, from class I (weak events) to V (extreme events). Storm occurrence probability was 96% for class I (i.e. almost one event per year) to 3% for class V. The return period for class V was 25 years and ranged from 6 to 8 years for classes III and IV storms, e.g. significant and severe events. Approximately 40% of the change in monthly wave data and storminess indices was related to several teleconnection patterns, the most important drivers of change being the Arctic Oscillation (AO), 21.45%, and the North Atlantic Oscillation (NAO), 19.65%. Specifically, during the 2009/10 winter Levante beach experienced very energetic conditions, representing one of the storminess in the past 50 years. The main ecological and geomorphologic changes observed along the beach was associated with the first group of seven storms that occurred during the December-January period. Winter storms produced dune lowering and dune foot retreat of c. 25 m, erosion in the backshore and accretion in lower foreshore according to a beach pivoting mechanism at mean sea level. As a result, beach slope decreased from 0.024 to 0.018, and 18.40 m3/m of sand was eroded during the monitoring period. The results obtained in this work have wider applications for ocean and coastal management. It is suggested that methodology used can be easily applied in different areas where wave buoy data are available. In the same way, information obtained with this kind of work constitutes the first step in the development of coastal protection plans to preserve socio-economic activities from the impact of severe storm events.