DWSM-Mud: a sixth-generation 3D model of the Dutch Wadden Sea for hydrodynamics and mud dynamics : 2023 release

Upon request of Rijkswaterstaat (RWS), Deltares has developed a sixth-generation three-dimensional hydrodynamic model of the Dutch Wadden Sea, including the Ems-Dollard estuary and a part of the North Sea immediately north and west of the Wadden Sea. The hydrodynamic model is expanded with a set of processes to simulate fine sediment dynamics in the Dutch Wadden Sea. The development of this model is part of a more comprehensive project in which sixth-generation models have been developed for all waters maintained by RWS. An important difference with the previous fifth-generation models is the use of the D-HYDRO Suite (known internationally as the Delft3D Flexible Mesh Suite), the new software framework for modelling free surface flows, which was first released in 2015 and allows for the use of unstructured grids. During the initial Dutch Wadden Sea Model (DWSM) model development, preliminary versions of the larger domain Dutch Continental Shelf Models (DCSM-FM 100m and 3D DCSM-FM) were used. An assessment of the impact of recent developments of those large domain models to the results of DWSM made clear that several improvements needed to be included in a new, second version of DWSM. The new hydrodynamics-only release was developed and validated within KPP Modelschematisaties 2022. The model was updated with respect to the model bathymetry, tidal boundary forcing, meteorological forcing and numerous other adjustments and improvements. As part of SITO MAD07 Beheer, Onderhoud en Ontwikkeling (BOO) Waterkwaliteitsmodelschematisaties 2023, the DWSM-Mud fine sediment transport model, that was originally developed in 2020, was connected to the updated version of the hydrodynamic model. The set-up and performance of the fine sediment transport model is very similar to what it was in the first release. The present report deals with the model description of the second release of DWSM-Mud, including the validation results. This report builds upon the description of the hydrodynamic release of DWSM by Zijl et al. (2022). For external reference purposes, the name dflowfm3d-waddenzee_200m-j22_6-v1a is used for the hydrodynamic model. The name dflowfm3d_dwaq_slib-waddenzee_200m-j22_6-v1a is used for the combined hydrodynamic and fine sediment transport model.