Technique for Prediction of Sediment Discharge from a Torrent

Researches on Simulation Model for SedimentTransport on a Torrent

Abstract

A simulation model is built applicable to sediment transport in a torrent. Water contained in deposit on a torrent bed is considered in the equation of continuity since the sediment concentration is often high. Water flow into the torrent channel is calculated from rain falling on the slope, using hydrological analysis. The Meyer Peter-Müller equation is chosen as the sediment transport equation since it is comparatively fit to the experimental results in the transition region between bed load tran-sport and debris flow.
This model was examined on the basis of observed changes in deposits on torrent beds during a flood. The kinematic wave run-off model was used as hydrological analysis after it was tested by the results of the observation of stream flow. The model for sediment transport could be applied well to one torrent, but in the other torrent, the calculated value of sediment discharge was much less than the observed value. It appeared to be due to the occurrence of a very large debris flow. Calculation by Takahashi's equation for sediment concentration of debris flow was made for the latter. Although the value of sediment discharge was neary equal to the observed value, the fact that the deposits on the bed were eroded throughout its profile could not be explained by the calculation.
This model can be applicable to the case that deposition occurs at the concave sections of the torrent bed profile and erosion occurs at the convex ones. The case of bed load transport and that of small debris flow seem to be simulated under this model.