Stokes, C.H., Russell, P., Conley, D., Beaumont, E., Greaves, D., 2013. Exploring Monthly To Seasonal Beach Morphodynamics Using Empirical Orthogonal Functions.

Empirical Orthogonal Function (EOF) analysis is a statistical method that can separate out the dominant modes of change in beach topographic data. Here the method is applied to four years of monthly intertidal survey data from Perranporth beach (Cornwall, UK), a predominantly dissipative site, which exhibits episodic low tide bar-rip morphology. The aim is to understand the main morphodynamic changes by studying only the dominant EOF patterns. Gridded data from 48 surveys was analysed and two statistically significant EOF modes were identified. The primary EOF (EOF1) has been interpreted as a seasonal ‘beach volume function' and shows that alongshore-uniform gains and losses of sediment, predominantly from the mid intertidal region, account for almost 50% of all the variability that occurs in the data set. This occurs with an annual periodicity, and the increasing trend in the temporal signal has been associated with the long term (∼years) increase in volume that the beach is experiencing. The second EOF (EOF2), has been interpreted as the ‘dominant rip function' and indicates that the second most dominant mode of change (∼11% of the total variability) involves the development of a recurring low-tide rip channel accompanied by a steepening of the beach and an increase in 3D structure.