Numerical investigation of siltation patterns in Hong Kong waters

In recent years, activities such as construction of jetties and sewage outfalls, dredging of marine mud and reclamation along coastline have increased tremendously and these activities may have significant impact on the siltation pattern. Three-dimensional numerical simulations of sediment transport processes in Hong Kong waters have been carried out for a one-year period including a wet season and two dry seasons. The computed results were used to investigate the siltation patterns due to the new coastline configuration and sewage outfalls. A comprehensive commercial numerical model, DELFT3D, was applied in the simulations. The siltation rates in various time and locations were obtained by summing up the local bedload flux and the net resuspension/deposition flux at the sediment-water interface. The computed net one-year siltation rate indicates that the siltation pattern is in long-term equilibrium especially in some natural navigation waterways. Siltation rate of up to 2 cm per annual is found in the northwest part of Hong Kong near the new Click Lap Kok Airport.