THE BORDERS OF THE RIDGE FORMS OF SEDIMENT MOVEMENT

Abstract

The article describes the active equilibrium motion of bed forms, which occurs in rivers during high water periods. The authors consider the relation between an average size of the particles of which little bed-forms (rifles) are formed and an average size of non-cohesive material in case of which armoring is formed in a river. These particles have a diameter of 0.5…0.6 mm. This boundary is associated with different mechanisms of stability loss for smaller particles, for which the probability of weighing is greater than for the larger particles. The article offers the extrapolation of the dependence of the ratio of average speed to critical speed received by V.N. Goncharov at small depths (up to 0.2 m) at the depth of 5 m on the basis of the experiments presented by V. Rijn. It is shown that the ratio of the dynamic speed to its critical value decreases with the increase in the size of alluvial particles, for bed formation and wash moments. For the moments of bed formation reaching the maximum bed height (maximum resistance in the channel) and erosion of the bed-forms was well confirmed by the values of the dimensionless parameter (the ratio of average velocity to hydraulic size taking into account the flow regime) for a particle size of about 1 mm.