淤泥堆积抬高河床，不仅减少大坝使用寿命，而且增加洪水泛滥的可能性。

The resulting silt raises the level of the Yangtze riverbed, not only reducing the life of the dam, but also worsening the risk of floods.

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发生这些异常现象的根本原因是，本次洪水的含沙量大以及近几年河道淤积严重、河床明显抬高。

The basic reason of these abnormal phenomenas is caused by hyper-sediment concentration, severe deposition of the channel and obviously increased the river bed.

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第一，过度砍伐引起的河流上游的侵蚀，第二，严重的泥沙淤积抬高了主干道的河床。

First, erosion resulting from excessive deforestation in the upper reaches of the river. And second, heavy silting which raised the riverbed in the main channel.

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