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Analysis on the Evolution mechanism of the“steep slope and rapid flow”section
of Lujia waterway in the middle reaches of the Yangtze River
under new conditions of water and sediment

1 2 1 1
LI Ming ，HU Chunhong ，ZHOU Chengcheng ，PENG Songbai
（1. Changjiang Waterway Planning Design and Research Institute，Wuhan 430040，China；
2. State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin，
China Institute of Water Resources and Hydropower Research，Beijing 100038，China）

Abstract： The middle reach of the left branch of Lujia waterway is the bottleneck in the middle reaches
of the Yangtze River due to its famous phenomenon of steep slope and rapid flow in the dry season. Based
on the analysis of the measured data，this paper systematically studies the evolution mechanism and devel⁃
opment trend of the left branch in Lujia waterway in the past ten years. In Lujia waterway， because the
continuous lowering of downstream water level， the height of water level drop from inlet to outlet has in⁃
creased， and the water surface slope has been further concentrated in the middle reach of the left branch.
The velocity acceleration section with the length of 1.7km in the left branch is the core section of water
level control，which has the most obvious increase of water surface slope，and it is estimated that the maxi⁃
3
mum surface velocity in the 7000-8000m /s flow section has increased by about 1m/s since the Three Gorg⁃
es Reservoir operation. The strong anti-scouring ability of the riverbed is the precondition for maintaining
the phenomenon of "steep slope and rapid flow" in the middle reach of the left branch. This paper points
out that the riverbed in the jet section is mainly composed of gravels and pebbles with a wide size distribu⁃
tion， which are continuously scoured and cut down due to the aggravation of rapid flow， with a phenome⁃
non of short-range transport of gravels and pebbles. This paper also points out that the anti-scouring abili⁃
ty of the riverbed in the main scouring area has been weakened，which may lead to the damage of the ar⁃
moring layer， and there is a trend of further scouring in the jet section due to further more lowering of
downstream water level. This study attempts to provide technical support for the waterway maintenance and
regulation of Lujia waterway and even the whole gravel sand bed reach downstream of the Three Gorges
Reservoir.
Keywords： the Three Gorges Reservoir； Lujia waterway； steep slope and rapid flow； evolution mecha⁃
nism；gravel sand bed reach

（责任编辑：李福田）

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