Historical overview of 2D and 3D hydrodynamic modelling of shallow water flows in the Netherlands

This paper contains a historical overview of 2D and 3D hydrodynamic modelling in the Netherlands from the 1960s till now. It started in the 1960s with two-dimensional (depth-averaged) shallow sea modelling for practical applications of the Dutch government. The most important application was the Dutch 'Delta works' project, which was initiated after the February 1953 flood disaster in the Netherlands. In the late 1980s, three-dimensional shallow water modelling in the Netherlands started due of the advance in computing power. This was also needed for 3D water quality modelling. Two large software suites have been developed for modelling of shallow water flows in the Netherlands, namely Simona and Delft3D. These integrated systems contain software for modelling of hydrodynamics, water quality, morphology and waves. In this paper, we focus on hydrodynamic modelling. In literature, a lot of applications of Delft3D and Simona have been described. However, in none of these papers, the key features of the underlying hydrodynamic numerical method have been described, which have resulted into a good performance with respect to robustness, accuracy and computational efficiency. This paper therefore summarizes 'proven technology' in shallow water modelling with Simona and Delft3D that has been applied in the past decades in the Netherlands and abroad. From the 1960s till now, the hydrodynamic modelling in the Netherlands has been based on structured grids. In 2011, a transition started in the Netherlands towards unstructured modelling for shallow water flows, which will be discussed as well.