NUMERICAL SIMULATION OF FLOODING AND DRYING IN A DEPTH-AVERAGED TIDAL FLOW MODEL

Abstract

A refined numerical modelling scheme to simulate the flooding and drying of shallow estuarine reaches by repetitive tides is described. Interest has been focused on developing a technique which can be applied to relatively large grid space and time step models, and which may be particularly relevant to nested hydrodynamic modelling. Details are given of comparisons of water elevation predictions obtained for two different approaches in modelling flooding and drying, for an idealised one-dimensional estuary with a uniformly sloping bed and with extreme grid and time step sizes. As a result of these comparisons, a refined scheme which is particularly relevant to less time restrictive implicit models has been proposed. The proposed flooding and drying simulation technique has been applied to a two-dimensional coarse grid model of the Humber Estuary. The predicted water elevations and depth mean velocities have compared favourably with field measurements taken at four specific sites along the estuary, which would suggest that the technique is an improvement on an earlier scheme that gave unstable results for the Humber Estuary.