Prediction of the hydrograph of a debris flow

本研究旨在提出实际山涧泥石流水流线的预测方法。首先，提出了一套方程系统，用于预测河床坡度、宽度和厚度不同且由分级混合颗粒组成的河道中任意位置的泥石流流线。该系统不仅可以估计任意供水条件下泥石流的水流线，而且可以通过将泥石流颗粒分为粗粒和细粒组分来确定泥石流中颗粒浓度的变化。将该方程组应用于实验室实验和哥伦比亚内华达德尔鲁伊斯火山喷发所产生的巨大泥浆流，证明了它是一种有用的预测方法。其次，用运动波理论对日本Gamada河支流Shiramizudani河道中观测到的泥石流流线变形进行了比较。观测结果表明，通道下的峰值放电衰减很大，这一现象可以用理论解释。第三，针对天然坝崩塌产生的泥石流，进行了一系列室内试验。给出了河道坡度与泥沙体积和单位宽度水流流量的函数之间的关系，给出了河道是否形成天然坝的判据方程。实验中天然坝的破坏过程有两种不同的过程，每一种情况下溃坝所产生的洪峰流量是不同的。对这些过程的理论分析应在以后进行。

This study aims to present the methods to predict the hydrographs of debris flows in an actual mountain stream.First, a system of equations with which to predict the hydrograph of a debris flow at an arbitrary position in a channel whose bed varies in slope, width and thickness and is composed of a graded mixture of particles is presented. This system not only can be used to estimate the hydrograph of a debris flow under an arbitrary water supply but to determine the change in concentration of particles in the flow by separating them into coarse and fine components. Application of this system of equations to laboratory experiments and to the huge mud flow generated by the eruption of the Nevado del Ruiz Volcano in Colombia proved that it is a useful prediction method.Second, the deformation of the debris flow hydrograph observed in the channel of the Shiramizudani, a branch of the Gamada River, Japan, was compared with the kinematic wave theory. The result of observation showed large attenuation of peak discharge down the channel and this was successufully explained by the theory.Third, concerning with the debris flow genarated by the collapse of a natural dam, a series of laboratory experiments were done. The equation presenting the criterion whether a natural dam is formed in a channel was given as a relation between the slope of the channel and a function of the sediment volume and the stream discharge per unit width. There were two different processes in the failure of the natural dam in experiments and the peak discharge produced by the collapse of the dam in each case was different. The theoretical analysis of these processes should be done later.