Modelling of cohesive sediment transport in the Maasmond area

In the Dutch coastal zone, where the marine environment is highly dynamic owing totidal currents, wind-driven, wave-driven, and density-driven currents and waves, thecohesive sediment dynamics is always a great concern to transportation authority andcoastal managers. So far, a lot research has been contributed on the cohesive sedimentdynamics such as transportation, deposition and resuspension. In addition, the origin ofthe cohesive sediment is also of a great interest to researchers. In this study, I willexplore some underlying mechanics governing cohesive sediment dynamics with thehelp of numerical models based on Delft3D which is a powerful software packagedeveloped 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 originalmodel is simplified due to the limitation of relevant data. Through the comparison withthe measured water level, both of the simplified and original ZUNO models present agood performance. The simplification doesn't cause significant change on the simulatedresults compared with the original model. Based on scale-based philosophy of Vriend,the simulated water level and current velocity on corresponding grids are provided toanother model based on the RIJMAMO grid as boundary conditions. The RIJMAMOmodel is a local refinement for the Dutch coastal area.The hydrodynamics of the RIJMAMO model is completed with the boundary conditionextracted from the ZUNO model. Upon the calibration and verification againstSILTMAN data which contains measured data regarding to flow velocity and sedimentconcentration near the mouth of Maasmond which is adjacent to the approachingchannel of the port of Rotterdam, it indicates that boundary conditions provided by theZUNO model are appropriate for the RIJMAMO model. The wave and sediment modelsare introduced to the RIJMAMO model successively. After the calibration andverification of the wave and sediment models, the coupled model presents that thesediment dynamics relates much to the significant wave height.As a new function of Deflt3D, WAQ model coupled with FLOW and WAVE models isapplied into this study. Amongst them, WAQ model is used for versatile water qualitymodelling including physical, (bio)chemical and biological processes; FLOW model isused for simulation of multi-dimensional hydrodynamic flow and transport phenomenaincluding sediments; WAVE model is used for simulation of short-crested wavesnearshore. Compared with the modelled results by FLOW model used previously inwhich sediment model is executed as a process, WAQ model presents someimprovement on the modelled results. During the calm period, the sediment has moreresponse to the tide-induced shear stress in WAQ model than that in FLOW model,which can be attributed to the more processes included in WAQ model. Nevertheless,due to the limited time, WAQ model has not been calibrated further, in which there ismore potential to be exploited