Large-scale Coastal Behaviour in Relation to Coastal Zone Management

Marcel J.F. Stive The development of coastal erosion management addressing typical traditional erosion problems towards coastal zone management addressing the evaluation of alternative solutions to guarantee a variety of coastal zone functions on their economic time scale has necessitated the formulation of large-scale coastal evolution (LSCE) models. Using the coastal evolution of the Netherlands in the Holocene up to the present as an example and a test case, Stive et al (1990) formulated such a LSCE concept. The (more generally applicable) model applies to quasi-uniform coastal stretches. It accounts for morphodynamic processes from the shelf to the first dune-row, and integrates over coastal units of approximately 10 km alongshore length. The added value, compared to earlier published concepts or models, lies in the full inclusion of cross-shore and alongshore processes, and in the distinction between a with respect to sealevel rise instantaneously responding active zone and a noninstantaneously responding central shoreface zone. Relevant differences have been found to exist between coastal cells on the "closed" and the "interrupted" coast. An important conclusion is that the crossshore effective Bruun-effect is only of limited importance. This is especially true in the case of the interrupted coast. Longshore sand transport gradients are very large there. This is mainly related to the sand demand which is placed on coastal stretches adjacent to estuary mouths of those estuaries which tend to follow the sea-level rise.