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.