Modelling rhythmic morphology in the surf zone

Abstract

Coastal erosion is increasingly being prevented by the application of shoreface nourishments. Although they are applied successfully, their development and their impact on the coastal system is still difficult to predict. Especially the effects of shoreface nourishments on the already existing rhythmic bed forms in the surf zone are unknown. The importance of insight into the occurrence and behaviour of these rhythmic features in the surf zone lies in the fact that the rhythmic breaker bar topography might be mirrored on to the dry beach, thereby locally creating narrower and therefore weaker beaches. Besides, currents associated with these bed forms are hazardous for swimmers. The aim of this thesis is therefore to model these rhythmic morphological features in the surf zone with and without the presence of a shoreface nourishment in order to gain this insight. Using linear stability analyses and morphodynamic computations, it shows that, among others, the length of the shoreface nourishment is an important parameter for its impact on the length scale of the rhythmic bed forms in the surf zone.