Vertical And Horizontal Fine Sediment Accumulation During Fluctuating Flows: Outcomes From Flume Experiments

Fine sediments have the potential to impact both benthic and hyporheic ecology by processes such as scouring and abrasion or by clogging the interstitial pores. But fine sediments are also an important component of the bed material in gravel streams, having the capacity to move through the coarse bed at a broad range of flows and contribute to overall river functioning. The relationship between river flow and sediment accumulation in complex environments is not well understood and few examples of experimental studies to understand such dynamics exist in the literature. Following field experiments on fine sediments accumulation in fluctuating flows in the Kiewa River (Victoria, Australia), several experimental flumes were established to determine the extent of sediment accumulation related to fluctuating flows temporally watering and dewatering a gravel bar. Vertical and horizontal dynamic processes were linked to surface and subsurface flow dominance, respectively. The aim of the current study is to investigate the influence of inundation and dewatering on fine sediment accumulation rates. It is expected that high durations of inundation will induce the highest sediment accumulation presumably originated by vertical infiltration. However, horizontal fine sediment accumulation is also expected as a result of interstitial flows and pressure differences.