High-resolution numerical modelling of three-dimensional flows over complex river bed topography

This paper describes preliminary results from a method for the treatment of complex bed topography for the understanding of three-dimensional flow processes. It develops an established porosity-based method and couples it to high-resolution bed topographical data acquired using digital photogrammetry. The results provide quantitative data on flow processes that match and perhaps exceed current measurement capabilities, and so raise difficult questions for model validation. However, the detailed flow fields provided by the method allow us to develop current models for flow-form interactions in gravel-bed rivers. Of most importance, the method will allow us to enhance significantly the application of computational fluid dynamics to complex river bed morphology, for large eddy simulation, roughness parameterization, sediment entrainment and deposition studies, and understanding interactions between flow and vegetation in relation to conveyance studies. Copyright (C) 2002 John Wiley Sons, Ltd.