FIELD STUDIES AND MODELLING OF INTERACTION BETWEEN NEARSHORE CURRENTS AND BARRED COAST

摘要

The study is aimed at on the description of longshore and cross-shore currents at a bar crest and at an adjacent trough. Field measurements and theoretical modelling tested against and driven by the field data were carried out. The field data were collected during several field campaigns comprising a multi-bar coastal zone. The recent field investigations revealed some specific features of nearshore hydrodynamics, e.g. significant longshore current velocities not only in the surf zone but beyond its offshore boundary as well. These velocities occurred even during almost perpendicular wave incidence. On a second front, the cross-shore currents were found to be much depth-variable, with the velocities sometimes directed seawards at the bar crest and landwards at the bar trough. The phase-resolving sediment transport computations incorporated a three-layer model with the bedload layer based on the water-soil mixture theory and two sub-layers of suspended load. This sediment transport model was nested in the phase-averaged modelling framework of hydrodynamics. Sea bed changes were calculated from spatial variability of the net sand transport rate. The records of nearshore topography were investigated with Extended Empirical Orthogonal Functions (EEOF) to seek large scale, long-term morphodynamic patterns.