浮流砂による河床変動について

Abstract

In this paper, the author discussed the river bed variation due to the suspendedsediment which occurs under non-equilibrium condition.A rate of the river bed variation per unit area is considered to be w0｜C-Cs｜in whichwo, fall velocity of the suspended particle, C, actual concentration near the bed and Cs isthe concentration under the equilibrium condition which my be expressed as a function ofw0 and u* (shear velocity).The author obtained an equation calculating the variation of the sediment concentrationwith relation to distance under the non-equilibrium condition, by assuming the diffusioncoefficient constant in a section and using the vertical distribution of the sediment con-centration in equilibrium state for the first approximation.In the case of the transition from one equilibrium state (shear velocity u*0) to anotherstate (u*), the variation of the concentration is calculated from the parameters w0/u*0 andu*0/u*. The diagrams for the calculation are prepared in this paper. The above procedurewas applied to the experiment of the sedimentation in a reservoir in which case thesuspended sediment has a grain-size distribution, by dividing the grain-size for some grades.The variation of the concentration near the bed obtained by the calculation showed fairlygood agreement with the observed one.