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下白鹤滩位于重庆市北碚境内,是嘉陵江下游三峡出口的峡口汊流浅滩。洪水期一万多流量以7～8米/秒的速度,从河面宽度仅为220米的观音峡流出,将河床冲刷成深达30多米的深槽(江家沱)后,河面突然放宽至600多米,随即在水土沱受到两岸宽度仅为260米的对峙山咀的约束,使该河段形成一放一收、两头小中间大的“莲藕状”。由于水流的扩散和壅水的综合作用,河床质在滩段大量落淤,形成卵石边滩(称杆碛)和江心洲,见图1。
Lower Baihe Beach is located in Beibei in the territory of Chongqing, is the lower reaches of the Three Gorges Jialing exit Gap slip stream. Floods more than 10,000 flow rate of 7 ~ 8 m / s, from the river width of only 220 meters out of the Guanyin Gorge, the river bed washed into deep deep reaches more than 30 meters deep (Jiang Jiatuo), the river suddenly relaxed to more than 600 meters , Then Shuituo Tuo was confined by the confrontation of Shan Tsui with a width of only 260 meters across the Taiwan Strait, resulting in the formation of a “lotus-shaped” lump in the middle of the river. Due to the combined effect of water flow and slug, the riverbed mass is largely silted in the tidal flat, forming a pebble beach (called the bar moraine) and a river heart island (Figure 1).