In the Dutch coastal zone, where the marine environment is highly dynamic owing to tidal currents, wind-driven, wave-driven, and density-driven currents and waves, the cohesive sediment dynamics is always a great concern to transportation authority and coastal managers. So far, a lot research has been contributed on the cohesive sediment dynamics such as transportation, deposition and resuspension. In addition, the origin of the cohesive sediment is also of a great interest to researchers. In this study, I will explore some underlying mechanics governing cohesive sediment dynamics with the help of numerical models based on Delft3D which is a powerful software package developed by WL | Delft Hydraulics. This study starts with the large-scale modelling of the North Sea using ZUNO grid, which has been verified by WL | Delft Hydraulics. During this research the original model is simplified due to the limitation of relevant data. Through the comparison with the measured water level, both of the simplified and original ZUNO models present a good performance. The simplification doesn’t cause significant change on the simulated results compared with the original model. Based on scale-based philosophy of Vriend, the simulated water level and current velocity on corresponding grids are provided to another model based on the RIJMAMO grid as boundary conditions. The RIJMAMO model is a local refinement for the Dutch coastal area.