长江口三角洲演变与陆海水力要素量化关系

Quantitative relationship between Yangtze delta evolution and land-sea hydrologic features

为了研究河口水下三角洲演变与流域和海域水力要素量化关系,以长江口水下三角洲为例,分析流域入海水量、沙量、含沙量和海平面变化对三角洲演变的影响。结果表明:近期(1950-2011年)流域入海水量变化不大,沙量为阶梯性锐减,含沙量自1985年开始为减小趋势,海平面为阶梯性增加趋势;1985-2000年水下三角洲经历了淤涨和冲刷交替变化,其中1997-2000年的淤涨为流域入海水量增加所致,2000-2009年期间呈现持续冲刷趋势;建立了三角洲演变与流域和海域水力要素关系曲线,流域入海水量、沙量和含沙量的增加有利于三角洲面积淤涨,海平面上升则使得三角洲表现侵蚀;流域入海水力要素变化对三角洲淤涨的影响大于海域,尤其是水量的影响,即三角洲演变过程中流域入海水力要素的影响占主导作用。

This paper presents an analysis on the influences of sea-going water and sediment, sediment concentration and sea-level change on the evolution of undersea estuary delta in the Yangtze estuary, and examines how the evolution is quantitatively related to the river basin hydrologic features and the East China Sea hydrodynamics. The results show that, during recent years （1950-2011）, the annual volume of sea-going water changed little while its sediment loading had a stepped and sharp decrease. Since 1985, the sediment concentration has tended to decrease and the sea level has shown a stepped increase. From 1985 to 2000, the undersea delta experienced accretion and erosion alternately, an accretion from 1997 to 2000 that was caused by an increase in the sea-going water volume, and a continuous erosion from 2000 to 2009. We established a quantitative relationship of the delta evolution versus the river and sea features, and it shows that the increases in sea-going water and sediment and sediment concentration play a positive role in the area accretion of delta, and the sea level rise induces delta erosion. The influence of river basin is greater than that of the sea, with runoff volume as the most significant factor, or the hydrologic features play a dominant role in delta evolution.