Modelling marine sand extraction pit evolution: Exploring design parameter sensitivity and cohesive sediment effects

Marine sand extraction increases, calling for insight into the morphodynamic evolution of extraction pits and other bed forms, such as sand waves. We developed a quick, idealized, process-based numerical model to (1) simulate pit evolution; (2) quantify sensitivity to pit design parameters; (3) investigate interactions with cohesive sediment; and (4) explore sensitivity to pit location on the Netherlands Continental Shelf. In line with observations, results show how extraction pits either fill in or trigger sand wave formation within and around the pit. The cross-stream pit size primarily controls the extent of sand wave formation. Strikingly, the perturbed area relative to pit area decreases for larger pits. Cohesive sediment slows morphodynamic evolution and accumulates within the pit. Pit location influences the evolution trough local sediment properties and hydrodynamic conditions. Despite being limited to the initial morphodynamic response, the low computational cost enables extensive exploration of the parameter space.