Sandbars in alluvial channels: their formation processes and interaction with groins

Abstract

Large sandbars resulted from the instability of loose sedimentary materials are very common in lowland rivers. These, not only, interrupt the inland waterways at low flow, but also make the channels highly unstable forming anabranches, influencing bank erosion, and so on. Groins have key roles to play in such cases. Formation processes of sandbars and their interactions with groins become very urgent to learn for better management of river engineering. RIC-Nays, a two-dimensional model for flow and morphology, is utilized in this study. Computation results reveal that different initial conditions lead to different equilibrium states, and periodic boundary conditions with a small computation domain tend to stabilize multiple bars. Intrusion of groins accelerates the flow in the main channel, which triggers the sediment movement there. Thus the bars move downstream reducing their scale and finally they disappear from the main channel.