A comparison of 1D and 2D bedload transport functions under high excess shear stress conditions in laterally constrained gravel-bed rivers: a laboratory study

Abstract. Channel processes under high-magnitude flow events are of central interest to river science and management as they may produce large volumes sediment transport geomorphic work. However, bedload these conditions poorly understood due data collection limitations the prevalence physical models that restrict feedbacks surrounding morphologic adjustment. The extension mechanistic equations gravel-bed rivers has emphasised importance variance in both entraining (shear stress) resisting (grain size) forces, especially at low excess shear stresses. Using a fixed-bank laboratory model, we tested hypothesis collapses more simple function (i.e. with mean stress median grain high conditions. Bedload was well explained by (1D approach) calculated using depth–slope product. Numerically modelling account for (2D) did not substantially improve correlation. Critical dimensionless values were back-calculated higher 2D approach compared 1D. This result suggests critical relatively greater influence stresses, whereas 1D assumes is sufficient mobilise size. While have stronger conceptual basis, performs unreasonably Further work required substantiate findings laterally adjustable channels.