三峡工程蓄水运用前后长江中下游干流河道冲淤规律研究

Study of sediment deposition and erosion patterns in the middle and downstream Changjiang mainstream after impoundment of TGR

本文较为系统地对比研究了三峡工程蓄水前、后宜昌至大通河段干流河道冲淤规律,并与原预测成果进行了比较。1966年-2002年宜昌至大通河段河道冲淤纵向分布以城陵矶为界,表现为"上冲、下淤",平滩河槽冲淤总体平衡,"冲槽、淤滩"特征明显。三峡工程蓄水运用后,2002年10月至2010年10月长江中下游河道原有的冲淤相对平衡状态被打破,全程冲刷已发展到湖口以下的大通,河床冲淤形态转变为"滩、槽均冲",冲刷主要发生在宜昌至城陵矶河段;与实测成果相比,宜昌至武汉河段河床冲刷预测情况基本吻合,武汉以下河段则在定性上有所差异;坝下游冲刷的速度和范围大于论证阶段的预计,这主要与三峡入、出库水沙条件较原设计成果相差较大,长江中下游河道采砂活动增多和局部航道整治工程有关。

This paper presents a systematic study of the sediment deposition and erosion patterns in the Yichang-Datong reach of the Changjiang River mainstream for the periods before and after impoundment of the Three Gorges reservoir(TGR).From 1966 to 2002,Chenglingji was a boundary point of sediment deposition and erosion distribution over this reach,which showed a pattern of erosion in its upstream and deposition in its downstream.The transverse distribution of the reach took a pattern of relative deposition-erosion balance in the channel and shoal with the features of significant groove erosion and shoal deposition.From the TGR impoundment in 2002 to Oct.2010,this balance was broken obviously,and the reach experienced an overall channel scouring that gradually extended to Datong.As a consequence,a new pattern of erosion both in groove and shoal had developed with most of the channel erosion appearing in the reach from Yichang to Chenglingji.The predicted erosion capacity for the Yichang-Wuhan reach agreed well with the in-situ measurements,while for the reach downstream Wuhan,the predicted erosion was qualitatively different from the measured results.Comparisons indicate that the measured erosion intensity and the area of channel scouring were larger than the predictions.The reservoir′s actual inflow and outflow conditions of water and sediment that were different from the design conditions,should be the major cause of the prediction errors.Sediment mining in the middle and downstream Changjiang River mainstream and local projects of channel regulation could be another two influencing factors.