2DH mathematical modelling of morphological evolutions in shallow water

A class of compound mathematical models of transient morphological evolutions in shallow water is discussed, based on commonly applied horizontally two-dimensional formulations of the water and sediment motion in the coastal zone. Three major aspects of the composition of such models are considered, viz. the specific adequacy of the constituent models, the balance of the total model and the possibility of spurious interactions. The lacunae in the knowledge and the tools needed to judge a proposed model at these points are indicated.Examples of spurious interactions are described in further detail and techniques to trace and avoid them are given. These examples, concerning morphological evolutions without the influence of waves, show that the advective acceleration terms in the flow model play an essential part in the bottom evolution and its interaction with the current and that incorporation of the bottom slope effects on the sediment transport is indispensable in models with a local transport formulation.