Characteristics of Self‐Formed Straight Channels

Abstract

Laboratory experiments were conducted to study various aspects of the mechanics of self‐formed, stable, straight alluvial channels in the presence of bed‐load transport. The assumptions used for the formulation of the turbulent diffusion model of Parker (1978) were examined first. Velocity measurements indicated that the logarithmic law for rough walls is a valid approximation to the velocity profile, along normals to the boundary for the whole channel depth. The equivalent sand‐grain roughness, ks, is about 2d90. The experiments show that the turbulent‐diffusion model is more realistic for flow in a straight channel than the threshold‐channel model. Regime relations based on the straight‐channel model, and a resistance equation, predict accurately the center depth and the top width of a self‐formed straight channel. The shape of the bank is found to follow closely an empirically fitted exponential function that requires knowledge of only the center‐channel depth. Data obtained from other studies support the findings of the present work.