Author(s): Yunping Yang; Yitian Li; Lingling Zhu; Zhaohua Sun
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Keywords: Estuarine delta; Evolutional rule; Water discharge; Sediment discharge; Quantitative relationship; Changjiang River basin
Abstract: It is important to determine quantitative relationships between evolutions of an estuarine delta and water/sediment discharge in a basin, because it is a basis for understanding effects of basin water conservancy projects on physical factors in an estuary. According to recent data about estuarine deltas of Changjiang River, we established the relationship to describe quantitative relationships between deltaic evolutions and basin water/sediment discharge, identifying the contributions of water and sediment to deltaic evolutions. The results indicate that the water discharge of Changjiang River has not been significantly changed for years, while the sediment discharge was reduced sharply and periodically. With the rapid decrease of sediment discharge and the changes of water discharge, the whole delta of Changjiang River estuary experienced the evolution process of deposition, decreased deposition and erosion. It has shown continuous erosion in trend since 21 century. The critical conditions in the equilibrium state of deltas were determined by creating quantitative relationship curves between deltaic evolutions and basin water/sediment discharge. Among them, the enhanced water discharge inhibited the deposition of Sand Island (-5m area) in front of the delta, but it benefited the deposition of subaqueous delta (-10m and -20m areas). Moreover, the increased sediment load and sediment concentration was beneficial to the deposition of the whole delta. As to the contribution rate for deltaic deposition, water amount and sediment load contributed ~27% and ~73% , respectively. Sediment shows a bigger effect on the delta than water, but the impact of water cannot be ignored, especially its influence during flood periods in the Changjiang River basin.
Year: 2013