The main channel bed will scour if sediment amount from tributary debris is less than that the main stream can carry and the river evolution exhibits the characteristic of mountainous rivers.
当支沟泥石流输入主河的泥沙量小于主河的输沙量时，主河河床将下切，并逐渐恢复山区性河流的特征。
2
When dealing with the relationship between tributary and main channel during flood routing, the general method is to add the discharge of tributary to that of main channel of the same instant.