Title: Beach Oscillation, Rotation and the Southern Oscillation, Narrabeen Beach, Australia
Abstract: Narrabeen Beach is exposed to waves averaging 1.5 m and is very responsive to changes in both wave height and direction. In order to assess the nature and scale of beach change, the following data were analysed. Twenty-three years of monthly beach profiles taken at 5 locations along the 3.6 km long beach, daily directional deepwater wave conditions, together with the monthly Southern Oscillation Index, both for the same period comprise the data set. The maximum scale of shore-normal beach oscillation was 96 m (mean 73 m), while maximum volume changes (storm demand) was 243 m3/m (mean 193 m3/m). Longshore time series of profile deviations from the ensemble beach volume highlighted a relationship, whereby the northern profiles were out of phase (–0.8 correlation) with the southern profiles, suggesting a beach rotation around a neutral central profile. Principle component analysis (PCA) revealed that the 2nd component displayed a linear trend from a positive northern profile to a negative southern profile around the central fulcrum, and explained 60% of the variance, verifying the observed rotation. The rotation accounts for up to 15 m and 30 m3/m of the shore-normal beach change. Analysis of directional wave data and the Southern Oscillation Index (SOI) suggests beach change is driven both by changes in wave height (power) and subtle change in wave direction, both of which are positively related to the SOI.
Publication Year: 2001
Publication Date: 2001-03-23
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 56
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