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

为了弄清高河岸侵蚀的实际情况，我们继续对孟加拉国的卫星图像进行图像分析，并将其与地面事实进行比较，孟加拉国的大河在洪水期间造成严重的河岸侵蚀。对孟加拉国梅克纳河的洪水流量进行了数值模拟，以预测河岸侵蚀过程。模拟结果与现场观测结果吻合较好。因此，用该模型模拟了含河床荷载和悬移荷载的河床变化。计算出的河床变化表明有可能发生巨大的河床冲刷。采用简化Janbu法对河岸边坡失稳进行了分析。用推广Janbu方法的运动方程预测了不稳定岸段的行为。对河流水位变化对河岸边坡稳定性的影响进行了试验研究。测量了河岸表面、顶部和斜坡的气流速率。

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.