Equilibrium coastal profiles: II. Evidence from EOF analysis

The validity of the concept of coastal equilibrium depends upon a proof of the existence of equilibrium. In addition, the methods of calculating the actual equilibrium profile and the response time are required. This study evaluates equilibrium conditions using evidence from EOF (empirical orthogonal function) analysis of the coastal profile data (bed slopes and associated elevations) obtained from Poole and Christchurch Bays, southern England. The preliminary results show that the largest eigenvalue is much greater than the other eigenvalues and the temporally-related eigenfunction is stationary; this observation implies the existence of equilibrium. Further, the spatially-related eigenfunction associated with the largest eigenvalue is used to calculate the actual beach profile at equilibrium. Although the temporal eigenfunction may fluctuate, it recovers rapidly, indicating that the response time is short. However, further studies are required to determine the response time accurately. Contribution No 3335 from the Institute of Oceanology, Chinese Acodemy of Sciences. Project supported by the SCOPAC (UK) and the CAS (through the “Hundred Talent Programme”, No. A10970203)