SIMULATION OF LARGE-SCALE COASTAL CHANGE USING A MORPHOLOGICAL BEHAVIOR MODEL

Quantitative simulation of large-scale coastal behaviour (LSCB) is possible using a model based only on principles of sand-mass conservation and geometric rules for shoreface and active sand-body morphology. Dynamic processes are subsumed into a set of parameters that define the geometry of the active cross-shore profile which in turn can represent an entire coastal cell. The parameters, together with a set of local behaviour rules governing adjustments at discrete points along the profile, provide a simple formulation that is constrained by sediment mass balance to yield emergent, numerical solutions for profile kinematics. The emergent qualities of this shoreface-translation model are exemplified in simulation experiments on changes to sand deposits on the southeastern Australian coast and shelf during the post-glacial marine transgression. In another example, the model is used to simulate LSCB over engineering time scales at an idiosyncratic site. Both examples illustrate the over-riding importance of small residual sand movements that accumulate through time to cause LSCB. In comparison to gross sand movements, the residuals are too small to measure directly or predict on the basis of available theory. Exploratory (inverse) simulation provides a quantitative method for side stepping these limitations. The shoreface-translation model therefore is used as a tool to explore possible forms of coastal behaviour through an approach that incorporates available data along with theoretical considerations. Validation is not strictly possible for this type of inverse approach, so the degree to which a simulation reproduces observed features in nature is a measure of its success.