The Grand Canyon of the Nu River is the upper reach of the Salween River, and it is located on the eastern margin of the Tibetan Plateau. There were 187 debris flow gullies along the Grand Canyon of the Nu River, and debris flows from 53 of these gullies completely blocked the river. Debris flows have carried a large volume of sediment into the river since the Holocene and have formed high-density dams on the riverbed, with the maximum dam height exceeding 30 m. The Nu River comprises the repeated sections of straight flow connecting lakes and the debris flow dams that changed the movement and distribution of sediment in the river. In this paper, terrain data for debris flow dams were collected by Lidar, water depth data for the lakes were collected by an unmanned ship with a depth sounder, and the thicknesses of sediment deposits, both in the dams and in the lakes, were measured using a geophysical exploration method (EH4). The debris flow dams were stratified and had multi-stage stepped structures with high resistance because of repeated historical breaches of older dams and river coarsening, different from the structure of alluvial fans constructed by floods. The construction of debris flow dams and the sedimentation depths and volumes in the Grand Canyon were analyzed. The research shows that the high density of debris flow dams made the Grand Canyon stepped and the sedimentation rate greatly increased, reversing the Nu River Grand Canyon’s historical cutting trend.

中文翻译：

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密集分布的泥石流坝对青藏高原东缘怒江（上萨尔温江）大峡谷河流形态的影响

怒江大峡谷是萨尔温江上游，位于青藏高原东缘。怒江大峡谷沿线共有泥石流沟187条，其中53条泥石流完全堵住了河流。全新世以来，泥石流携带大量泥沙入河，在河床上形成高密度大坝，最大坝高超过30 m。怒江包括连接湖泊和泥石流坝的重复段，改变了河流中泥沙的运动和分布。本文采用激光雷达采集泥石流坝地形数据，配备测深仪的无人船采集湖泊水深数据，泥沙沉积厚度、在大坝和湖泊中，均使用地球物理勘探方法 (EH4) 进行测量。泥石流坝由于历史上老坝的多次溃决和河道粗化，呈分层结构，呈多级阶梯式结构，抗力较高，与洪水造成的冲积扇结构不同。分析了大峡谷泥石流坝的建设和沉积深度和体积。研究表明，高密度的泥石流坝使大峡谷呈阶梯状，沉积速度大大增加，扭转了怒江大峡谷的历史切割趋势。泥石流坝由于历史上老坝的多次溃决和河道粗化，呈分层结构，呈多级阶梯式结构，抗力较高，与洪水造成的冲积扇结构不同。分析了大峡谷泥石流坝的建设和沉积深度和体积。研究表明，高密度的泥石流坝使大峡谷呈阶梯状，沉积速度大大增加，扭转了怒江大峡谷的历史切割趋势。泥石流坝由于历史上老坝的多次溃决和河道粗化，呈分层结构，呈多级阶梯式结构，抗力较高，与洪水造成的冲积扇结构不同。分析了大峡谷泥石流坝的建设和沉积深度和体积。研究表明，高密度的泥石流坝使大峡谷呈阶梯状，沉积速度大大增加，扭转了怒江大峡谷的历史切割趋势。