Numerical Simulation of the Effect of Topographic Changes on Sandspit Intrusion Processes

The formation and evolution of a sandspit are subjected to changes in the prevailing hydrodynamic and topographic conditions at an estuary or bay mouth. In this study, we investigated how these changes impact the development of a laterally migrating or intruded sandspit. As an exploratory approach, we performed numerical simulations in the Delft3D model. The model domain and simulations were based on schematized bathymetries similar to a bay mouth with varied water depths. Model results showed that spits were formed parallel to the updrift shoreline for the shallow water depth scenarios. For the deep-water depth conditions, sandspit intrusion and sediment deposition along the headland were observed. Interestingly, the straight spits were formed because the water depth was less than the depth of closure for the shallow conditions whereas the reverse was observed for an intruded spit. The findings of the study could be useful for coastal management activities (spit breaching, estuary dredging or jetty construction) at river mouths and inlets. These activities have the potential to alter the sediment budget at a river mouth and therefore require careful considerations in the design depth for coastal structures.