Bed load sediment transport and morphological evolution in a degrading uniform sediment channel under unsteady flow hydrographs

Le Wang, Alan Cuthbertson (Lead / Corresponding author), Gareth Pender, Deyu Zhong

Research output: Contribution to journalArticle

65 Downloads (Pure)

Abstract

Flume experiments are conducted to investigate the intrinsic links between time-varying bed load transport properties for uniform sediments and bed surface morphology under unsteady hydrograph flows, in the absence of upstream sediment supply. These conditions are representative of regulated river reaches (e.g. downstream of a dam) that are subject to natural flood discharges or managed water releases, resulting in net degradation of the river bed. The results demonstrate that the hydrograph magnitude and unsteadiness have significant impacts on sediment transport rates and yields, as well as hysteresis patterns and yield ratios generated during the rising and falling limbs. A new hydrograph descriptor combining the influence of total water work and unsteadiness on bed load transport is shown to delineate these hysteresis patterns and yield ratios, whilst correlating strongly with overall sediment yields. This provides an important parametric link between unsteady hydrograph flow conditions, bed load transport and bed surface degradation under imposed zero sediment feed conditions. As such, maximum bed erosion depths and the longitudinal bed degradation profiles along the flume, are strongly dependent on the magnitude of this new hydrograph descriptor. Similarly, non-equilibrium bed forms generated along the flume indicate that formative conditions for alternate bars, mixed bar/dunes or dunes are defined reasonably well by an existing morphological model and the new hydrograph descriptor. These findings provide a new framework for improved predictive capabilities for sediment transport and morphodynamic response in regulated rivers to natural or imposed unsteady flows, while their wider application to graded sediments are also considered.
Original languageEnglish
Pages (from-to)5431-5452
Number of pages22
JournalWater Resources Research
Volume55
Issue number7
Early online date7 Jun 2019
DOIs
Publication statusPublished - Jul 2019

Keywords

  • bed load
  • bed morphology
  • flood hydrographs
  • flume experiments
  • sediment transport
  • unsteady flow

Fingerprint Dive into the research topics of 'Bed load sediment transport and morphological evolution in a degrading uniform sediment channel under unsteady flow hydrographs'. Together they form a unique fingerprint.

  • Profiles

    No photo of Alan Cuthbertson

    Cuthbertson, Alan

    Person: Academic

    Cite this