Effects of some parameterson numerical simulation of coastal bed morphology

Abstract

Purpose – The aim is to investigate in detail the sensitivity of sediment transport and bed morphology with respect to some parameters including bed slope, non-hydrostatic pressure term, sand grain size, temperature, salinity and lower boundary conditions for suspended sand concentration on a regional scale through numerical simulations based on a mathematical model. Design/methodology/approach – The numerical model consists of a 3D hydrodynamic code amended by a sediment transport module. At the same time, the influence of wave action has been taken into account. The model is applied to the Sylt-Romo tidal bay covering approximately 20 £ 30 km2 spanned by about 2.7 £ 106 active grid points with the constant wind and wave fields. Findings – The computed results of seven different cases over 150 h show that the effect of bed slope correction is very strong, especially in case of largely changeable bathymetry and depends on the horizontal grid resolution. Sand grain size strongly influences the vertical distribution of suspended sediment and then sedimentation.The impact of seawater temperature is relatively clear despite being less powerful than two former parameters. Non-hydrostatic pressure perturbations of the flow field and the kind of the lower boundary condition aswell as salinity are negligible allowing for considerable savings of CPU time when the numerical simulation is carried out for a large area and for a very long-time period. Originality/value – The results of the study demonstrate that the geometrical factor of coastal bed and the range of sand particle size on the bottomcontribute to the tendency of bed evolution in some measure. Additionally, the increase of temperature of sea water due to global warming may also make a considerable change to the mechanism of sediment transport and sedimentation in future. Therefore, the human intervention in the process of natural evolution is possible through the behaviour to the nature. At the same time, this is also interesting and useful information and it can consolidate the idea for coastal engineering projects.