文章摘要
三峡水库运行后宜昌-城陵矶河段冲刷重心下移与时空演变
Spatio-temporal channel evolution and the migration of erosion center in Yichang-Chenglingji Reach after the operation of the Three Gorges Project
投稿时间:2021-02-08  修订日期:2021-09-03
DOI:
中文关键词: 三峡坝下游  宜昌至城陵矶河道  冲刷重心  时空冲淤  空间聚类
英文关键词: Three Gorges Dam  Yichang-Chenglingji Reach  erosion center  spatio-temporal evolution  spatial clustering
基金项目:国家自然科学基金项目(面上项目,重点项目,重大项目)
作者单位邮编
王华琳 武汉大学 430072
郑珊 武汉大学 430072
谈广鸣 武汉大学 
李凌云 长江科学院河流研究所 
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中文摘要:
      三峡大坝下游河道的冲刷发展影响着长江中下游的防洪、航运及区域经济发展。本文以宜昌至城陵矶河段约400km长河段为研究对象,基于2002?2018年河道的来水来沙、泥沙粒径和横断面形态观测资料,计算并分析河道垂向冲淤、横向摆动、平滩面积、平滩水深和冲淤量的变化,根据河道平面形态将研究河段划分为32个子河段,对子河段平均平滩面积和平滩水深的变化速率进行分级,引入空间聚类分析方法,对冲刷强度等级最高的河段在时空尺度上分布进行聚类分析,研究河道冲刷重心的时空迁移规律。结果表明,时间上,三峡水库运用后下游河道经历了蓄水初期冲刷较强(2003?2007)、175m正常蓄水运用后冲刷减弱(2008?2012)和上游梯级水库运用后冲刷增强(2013?2018)的三个阶段;空间上,宜昌至枝城及上荆江河段普遍冲刷,以弯曲型为主的下荆江河道以冲为主,但冲淤交替频繁,同时冲淤强度具有随时间衰减的特点;冲刷重心具有向下游迁移的趋势,在三峡水库蓄水初期冲刷重心向下迁移较快,之后减缓,上游梯级水库运用后,冲刷重心下移速率明显加快,之后再次减缓,2003?2018年冲刷重心平均下移速率约7.5km/a。
英文摘要:
      The erosion development of the channel downstream of the Three Gorges Dam (TGD) affects the flood control, navigation and economic development of the middle and lower reaches of the Yangtze River. However, the quantitative research on the temporal and spatial evolution of the erosion center (i.e. the reach with high erosion intensity) in the downstream of the dam is still insufficient at present. Based on the data of water discharge, sediment load, bed material size and cross-sectional surveys, we analyzed the vertical, lateral and bankfull channel geometry changes in the Yichang-Chenglingji Reach (about 400 km) downstream of the TGD. The channel was divided into 32 sub-reaches according to the planform and the changes in bankfull area and bankfull depth were classified into different levels. A spatial clustering analysis method was introduced to study the distribution of the sub-reaches with highest erosion level and analyze the migration characteristics of the erosion centers. The result indicated that, temporally, the channel downstream of the TGD experienced fairly strong erosion during the initial impoundment of the Three Gorges Reservoir (from 2003-2007), weakened erosion after the reservoir was operated with normal pool level of 175 m (2008-2012), and then, enhanced erosion after the cascade reservoirs upstream of the TGD started to operate (2012-2018). Spatially, upstream sub-reaches were generally eroded while transition between degradation and aggradation was common at the downstream reaches. The meandering lower Jingjiang reach was generally in the 4th zone, where the channel degradation and aggradation alternated frequently, but the degradation and aggradation rates decayed as time elapsed. The erosion centers tended to migrate downstream and the migrating rate of the erosion center was fast during the initial operation period of the TGD, then slowed down, accelerated following the operation of the cascade reservoirs upstream of the TGD, and slowed again a few years later. The average migrating rate of the erosion center during 2003-2018 was 7.5km/a.
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