Modelling of cohesive sediment transport with the PCFLOW3D model

Abstract

The processes in cohesive and non-cohesive sediment transport differ from each other significantly.\ud Different types of sediments are defined by different parameters. Pečovnik (2014) noted that the\ud PCFLOW3D model does not simulate transport of cohesive sediments correctly. We suggest a simple\ud equation which is appropriate for calculating cohesive sediments and does not contain additional\ud measured parameters. We integrated the equation in the PCFLOW3D model and tested the upgraded\ud model. We calculated critical shear stresses for cohesive and non-cohesive sediments and performed\ud simulations with combinations of different circulation patterns and wave parameters. Non-cohesive\ud sediments begin to resuspend at 0.5 m high waves, while cohesive stay at the bottom until waves reach\ud the height 0.9 m. Furthermore, the areas and the intensity of resuspension differ significantly. Using the\ud adopted data, the majority of bed-shear stress is induced by waves, whereas wind-induced currents\ud contribute only an insignificant part. However, the wind direction affects the direction of currents and\ud subsequently the direction in which suspended material is transported. We also depict the depth averaged\ud concentrations of suspended material. The results are close to our expectations; the concentrations are\ud increasing proportionally with wave height. Areas with the highest concentration of suspended sediment\ud occur in places with the largest shear stress