Co-variability of bars in a multi-bar nearshore zone determined with canonical correlation analysis (CCA)

Nearshore bed variations of the southem Baltic shore were investigated with the aim of detecting co-variability among bed forms of a multi-bar system. The studied area is located at IBW PAN Coastal Research Station at Lubiatowo. The beach consists of fine sand of median grain equal to 0.22 mm, is mildly sloping and boasts multiple (usually 4) bars, which is typical for the coast in the southem Baltic. Data on bed topography were collected along 27 lines, equally spanned every 100 m, since 1987 to 1999, usually twice a year. Fairly high alongshore bed homogeneity made it possible to choose one representative profile for which the CCA method was employed. The method demonstrated considerable potential for detecting co-variability of bed features in the nearshore zone. The results show that some 80% of variability in the region of the offshore slope of the outermost bar can be attributed to variations of Dean equilibrium profiles. The portion of variability of the two innermost bars due to variations of equilibrium profiles equals 40%. Horizontal counter-movements of outer and inner bars can be responsible for same 20%. The remaining 40% should be related to highly variable short time scale phenomena like breakers and wave driven currents in the vicinity of inner bars.