长江口河势近15年变化特征及其对河口治理的启示

1998年长江口深水航道治理工程实施以来,开展了常年定期的长江口河势跟踪监测分析工作。基于此,从宏观角度系统分析和总结了长江口河势近15 a来的总体变化特征,并探讨了河势演变特征对后续河口治理开发的若干启示。结果表明:近15 a来长江口河势变化整体仍符合陈吉余等1979年提出的河口历史发育模式;长江口深水航道治理工程、青草沙水库等重大涉水工程建设对稳定“三级分汊、四口入海”的河势格局起到了重要作用;在2007年之后长江口河床冲淤调整程度总体趋于放缓,年内冲淤变化受径流过程影响仍较明显。从河势发展的角度看,未来长江河口的治理开发,须继续遵循河口向东南方向的演化趋势,综合考虑河口开发的相互影响,以及加快长江口综合整治开发等规划的实施步伐。

Characteristics of River Regime Variation of Yangtze River Estuary in the Past 15 Years and Their Enlightenment on Estuary Regulation

Since the construction of Yangtze Estuary Deepwater Channel Regulation Project began in 1998, tracking survey and analysis on the river regime of Yangtze Estuary have been carried out regularly. On this basis, the characteristics of overall river regime variation of Yangtze Estuary in the past 15 years are analyzed and summarized systematically from macro perspectives. Some enlightenments of riverbed evolution on estuary regulation are also discussed. Results show that the river regime variation in the past 15 years is still in overall accordance with mode of estuary’s historical development proposed by Chen Ji-yu et al(1979). Major hydraulic projects including the Yangtze Estuary Deepwater Channel Regulation Project and the Qingcaosha reservoir play an important role in keeping the stability of river pattern(three-order bifurcations and four outlets into sea). The adjustment of bed erosion and deposition in the Yangtze Estuary tends to slowdown after 2007 in general, and the effect of runoff process on in-year change of erosion and deposition in the Yangtze Estuary is still obvious. Future regulation on the estuary should be in accordance with the trend of evolving towards the southeast direction, the interaction effect of estuarine works should be considered, and the implementation of comprehensive regulation planning should be accelerated.