Erosion Process of High River Bank Exposed to Large Water Level Changes

为了弄清孟加拉国高岸侵蚀的实际情况，继续对孟加拉国的卫星图像进行图像分析，并与地面实况进行比较，孟加拉国的Meghna河洪水流量进行了数值模拟，预测了河岸侵蚀过程。这些模拟结果显示出良好的协议现场观测。应用该模型模拟了有推移质和悬移质的河床变化。计算的河床变化表明，河床可能会发生大的冲刷，采用简化的Janbu法分析了河岸边坡的失稳。通过扩展Janbu方法的运动方程，预测了不稳定岸段的运动规律，并对影响河岸边坡稳定性的河岸内部气水运动规律进行了实验研究。测量了来自河岸表面、顶部和斜坡的空气流速。

In order to clarify actual state of high bank erosion, image analyzes of satellite imageries has been continued and compared with ground truths in Bangladesh, where large rivers cause severe bank erosion during flood.Numerical simulations have been carried out on flood flows in the Meghna River, Bangladesh to predict bank erosion process. Results of these simulation show good agreement to field observations. Hence'river bed variations have been simulated by using this flow model with bed load and suspended load. Calculated bed variation indicated possibility of enormous bed scouring.Instability of river bank slope was analyzed by a simplified Janbu method. Behavior of unstable bank fraction was predicted by a equation of motion extending the Janbu method.An experiment was carried out on air-water behavior inside of river bank, which affects stability of river bank slope, corresponding to river water level changes. Air flow rate from the bank surface, top and slope, was measured.