MORPHOLOGICAL DEVELOPMENT OF NEARSHORE BED-FORMS

A morphodynamic stability analysis of a straight, barred coast with waves normally incident on it is undertaken. The analysis includes (period- and depth-averaged) hydrodynamics: continuity and momentum equations, energy and phase equations for the short waves, and a bed evolution equation. Results show the development of a system of rip channels (with associated rip currents) and shoals on the shore-parallel bar, and the concurrent development of a transverse bar system attached to the coast, which appear to agree with observations. Numerical experiments suggest that in this case the morphodynamic instability is initiated over the bar, the transverse bar system being just a forced phenomenon which is induced by the growing rip channel system. The energy and phase equations are necessary to model this phenomenon.