ABSTRACT
Gravel mining has been prohibited in the reaches of severe riverbed degradation, and the tendency to degrade is now moderated. However, because sediment supply is still intercepted by dams, the riverbeds downstream are armor-coated and a scarce amount of sediment is transported. This situation is harmful to aquatic habitat. Some rivers transformed their channel pattern from the braided channels to the meandering channel which resulted in the extreme local scouring of the foundations of bridge piers and levees. Reservoir operation reduces the discharge of flood flow. Thereby the stabilization of sandbars is caused. A stable sandbar stimulates the tree growth on it, which diminishes the flood conveying capacity of the river.
