COMPLEX PRINCIPAL COMPONENT ANALYSIS TO CHARACTERIZE BEACH TOPOGRAPHIC CHANGE IN SILT ISLAND, GERMANY

摘要

To predict topographic changes is indispensable for developing a long-term coastal management plan, in particular for the coasts where sandy beaches are dominant. A number of models have been developed so far to predict beach topographic changes, based on the physical principles associated with the interaction between waves and sediment movements. However, these models cannot be applied directly to large-scale coastal areas with a length of more than several tens kilometers, for they cannot represent all the local conditions and need a huge computational capacity. On the other hand, the correlations between incident waves and long-term topographic changes are relatively easy to obtain by a statistical analysis. The correlations can be used to predict future coastal topographic changes. For the prediction, predominant patterns of the topographic changes must be analysed in details at first. Statistical methods have been developed for analysing beach profile data since Winant et al. (1975) applied the principal component analysis (PCA). The validity of the methods of this kind is confirmed in relatively narrow coastal area, for instance, around a port (Bosma and Darlymple, 1996; Yokoki et al., 1998), whereas the applicability to much wider areas has not been verified yet. The purpose of the present study is to analyse statistically the coastal topography data obtained in Sylt Island coast, Germany, by the complex principal component analysis (CPCA), and to examine the applicability of CPCA through these analyses. To investigate the characteristics of beach topographic changes after beach nourishment in Sylt Island coast is another purpose of the study.