SOME TECHNIQUES AND RESULTS FROM NUMERICAL HYDRODYNAMIC MODELLING OF SHALLOW WATER SYSTEMS

Three new techniques concerned with the modelling of currents in shallow water systems are discussed. The first technique considers the problem of whether, for a specific basin, 3-D water quality modelling is necessary, or whether 2-D modelling (in plan) will suffice. It is shown, using a simple hydrodynamic model, that, for natural bathymetries, 2-D modelling would appear to be adequate. The second technique involves the use of topographically-controlled wind-driven horizontal gyres in improving the flushing of a small bay, marina or harbour. Suitable criteria for the design of a dredged channel are derived. The third technique involves the development of a new method for parameterising bottom friction in 2-D (in plan) models. This method, yields the exact steady-state solution of the full 3-D linear hydrodynamic equations. It entails only a small computational overhead in comparison with conventional methods.