Stable width and depth of straight gravel rivers with heterogeneous bed materials

Mathematical model for defining stable width and depth of straight gravel rivers is presented, in which it is revealed that the major agency for maintaining stable channel is lateral diffusion of longitudinal fluid momentum due to turbulence. The primary quantities which determine the stable channel geometry are found to be flow discharge, longitudinal free surface slope, the median size of bed material, and gradation of the bed material. Increasing gradation is found to increase the depth and decrease the width. Introduction of one loose and the other rigid bank in laboratory experiments provides good examples to test the model, in which four kinds of sand were used to test the gradation effect. These laboratory data support the mathematical model presented herein. The theory also performs well when it is applied to natural gravel rivers.