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 inyear 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.