Changjian (Yangtze) River Delta, China
Keywords:Changjiang delta, coastal geomorphology, estuaries, floods, management, subsidence, sea level, Yangtzee
After a brief review of the previous studies and a description of the geographical setting of the Changjiang River, the Changjiang River delta, and the Changjiang River estuary, this paper first summarizes the geological framework in which the recent vertical tectonic movement is emphasized because of its close connection with relative sea level changes and earthquakes. A systematic description of the stratigraphy reveals the local geologic history. Sedimentary sequences, facies and structures since the Holocene are next briefly reviewed. The historical delta and coast development is examined, with special reference to the coastal response to sediment supply. Recent achievements on the physical and biological processes in estuarine and coastal waters are presented. These processes are found to greatly influence the temporal and spatial variation of water salinity, suspended sediment concentration, sedimentation rate, and primary productivity. The interaction of natural processes with socioeconomic development is discussed in detail, with an emphasis on the major problems of estuarine freshwater resources and the impact of water diversion, harbors and navigation channels, land shortage and the impact of land reclamation, subsiding ground surface, rising sea level and flood hazards. Finally, the probable delta development in the coming decades in response to several large scale engineering works is discussed, such as the Three-Gorges Dam, the planned water transfer to North China, and the Deep Water Navigation Channel.