Abstract: Fluctuation process of river discharge is a key factor to channel evolution, and discharge variation
is common in natural rivers. In this study, physical model tests and fine measurements of river flow have
been conducted to investigate channel evolution under discharge variations, with three sets of test conditions
arranged, i.e. constant discharge, gradually varied discharge, and rapidly varied discharge. The results show
that, shoal-pool structures develop in the channel under a combination of initial bending and secondary flow,
covering two typical areas: the higher one that deflects the main flow, and the lower one that are sheltered.
Fluctuations in discharge can destroy the existing shoal-pool structures, causing flatter shoals and shallower
thalwegs, and the fluctuations of greater mean square deviation has greater bank erosion power hence
leading to a wider river channel.