Decadal Scale Patterns in Beach Oscillation and Rotation Narrabeen Beach, Australia—Time Series, PCA and Wavelet Analysis

Twenty-six years of monthly beach profiles located along 3.6 km Narrabeen beach were analyzed using time series, principle components (PCA) and wavelet analysis. The time series reveal both beach oscillation (erosion-accretion) and rotation between the boundary headlands. The rotation phenomenon is confirmed by the 2nd PCA component, explaining 58% of the remaining data variance. The scale of beach oscillation is on the order of 70 m, with 30 m of this oscillation attributed to beach rotation. Continuous wavelet transform analysis identified decadal scale patterns in beach response. This analysis indicates that variability in ensemble beach width and beach rotation exhibit long-term non-stationary variability. Longer-term cycles of behavior in overall beach erosion/accretion and beach rotation appear to coincide with each other, while short term fluctuations suggest a variety of physical processes are responsible for beach width variation and the interannual rotation phenomenon.