Abstract
Principal component analysis (PCA) and complex PCA (CPCA) are applied to examine medium-term geomorphological behavior of an exposed sandy beach before Gamo Lagoon located at the mouth of Nanakita River along Sendai Coast, Japan, using a 12-year series of bathymetry survey data. The results of PCA and CPCA for the bathymetry data set show that erosion and subsequent accretion of the submerged terrace formed in front of the river mouth appear in the first mode of CPCA and have the most significant influence on the medium-term geomorphology of the study area. The first mode is mostly caused by northward alongshore sediment transport driven by wave energy flux, explained from the observed wave data. The second mode of CPCA demonstrates that the sediments previously discharged from the river would return again into the nearshore region, and furthermore, the topography changes due to cross-shore sediment transport emerge in the third mode of CPCA.
