Process-response modeling of wave-dominated coastal systems: Simulating evolution and stratigraphy on geological timescales

Numerical modeling on a geological timescale is a rapidly expanding tool to investigate controls on formation of the stratigraphic record. Modeling enables us to test existing ideas, but verification of model results is commonly difficult. Many models are based on geometric or diffusion rules, yet neither type of model has much relevance with actual processes that control sedimentary systems. Here we describe a process-response approach to model the evolution and stratigraphy of wave-dominated coastal systems in two dimensions, based on simple approximations of cross-shore erosion and sedimentation. Separating erosion and deposition functions enables us to simulate coastal evolution, stratigraphy, erosion surfaces, and transport of multiple-grain-size classes. The simulated stratigraphic record contains detailed information on grain size and stratal geometry. We calibrated the model with data sets on coastal transgression in the Caspian Sea, Dagestan, and on grain-size distributions at the island of Terschelling, The Netherlands. Furthermore, hypothetical examples are presented to show the effect of changes in sea level and sediment supply, substrate slope, and sediment size distribution. These tests show that the model is capable of reproducing widely accepted conceptual models of coastal evolution on geological timescales (progradation, aggradation, and various modes of retrogradation).