Should we aim towards a unified framework for sediment transport along riverbeds?

Sandra Soares-Frazao 

Transport of sediments along a riverbed can take various forms depending on the grain-size distribution and the flow conditions, ranging from bedload to sheet flow and debris flows. Modelling such flows poses several challenges. Indeed, each type of flow requires an appropriate mathematical modelling framework. Simple bedload consisting of grains moving along the bed can be efficiently modelled considering only sediment continuity in the bed, while more intense transport requires to account also for inertia effects in the moving sediment layer that interact with the water flow. If suspended load is observed in addition to bedload, or in case of heavy transport along the whole water column, the flow can be considered as a two-phase flow where interactions between the liquid and solid phases must be considered. In this presentation, we will investigate different modelling options adapted to these flow situations, highlighting the key features of these models by comparison with laboratory experiments designed for these different cases. The key discussion point is then to find a trade-off between the model complexity and its suitability for real situations, beyond idealised experiments.