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NERC funded research: sediment structure and river morphology

NERC funded research: sediment structure and river morphology

The stability or mobility of a river bed has long been seen in terms of the balance between flow strength and the resistance of sediment to movement. In gravel bed rivers, this balance determines the persistence of channel forms such as riffle-pool sequences. Sediment resistance to movement (quantified as critical shear stress, τc) is typically quantified in terms of easily-measured grain size. However, past and recent research has shown that the structural arrangement of sediment grains in the river bed exerts a first order control on τc, and thus sediment transport and bed stability. In order to understand how the morphology of the river bed develops and evolves, we need to understand the role of sediment structure; but, until recently, quantifying 3D sediment structure has been limited by the available techniques. This proposal will apply state-of-the-art techniques to produce new quantitative measures of 3D sediment structures in both the field and laboratory in order to evaluate both the evolution of 3D sediment structure under different controlling factors (the infiltration of fine sediment and the local channel morphology), and the consequent impact of the resulting pattern of sediment structure on the development of river bed morphology.