A dedicated tidal stream atlas of the stratified tidal flows near Stonecutters Bridge, Hong Kong, based on 3D numerical simulations with HLES

Construction works at the Stonecutters Bridge crossing the Rambler Channel in Hong Kong involve bridge deck lift operations with dynamically positioned barges. Nautical simulations for marine safety assessment and the programming of the bridge deck lift operations require reliable predictions of the local currents. To that purpose, we designed a detailed hydrodynamic Delft3D-FLOW model for simulating 3D stratified tidal flow and larger-scale eddy-dynamics using Horizontal Large Eddy Simulation (HLES). This model was nested in the 3D hydrodynamic model of the Pearl River estuary and the Hong Kong waters, which has been extensively calibrated and validated in other studies in the Hong Kong area. The results of the detailed model show good agreement with dedicated field measurements for both the dry and wet seasons. Based on tidal analysis of the model results, predictions for the water levels and currents could be made that include the complex flow patterns and (tidally driven) eddies and recirculations. For easy prediction of the flow conditions in the future, a digital tidal stream atlas (Delft-STREAM) was set up that is capable of predicting these flow fields. This tool provided a valuable contribution to the programming and execution of the marine works of Stonecutters Bridge. The new development in this study is the inclusion of complex 3D flow patterns into a digital tidal stream atlas, capable of predicting detailed flow fields for construction planning purposes.