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长江口水下三角洲采集的两个柱状样放射性核素137Cs分析表明,长江口水下三角洲137Cs剖面中均存在清晰的最大蓄积峰,与1963年的137Cs散落沉降相对应,剖面中同时存在可对应于1959年的较清晰的次级蓄积峰,由此计算得到1959—1964年长江口水下三角洲的平均沉积速率为2.4~4.8 cm/a,1964—2006年减小到1.4~1.8 cm/a。反映出长江口水下三角洲整体淤积速率有很大程度的减小,很可能是三峡蓄水导致流域来沙量大幅度减小所致。虽长江口水下三角洲各处淤积速率减小程度不同,但降低的速度很快,表明长江三角洲发育已出现重大变化,水下三角洲局部地区已观察到侵蚀现象。
137Cs analysis of two columnar radionuclides collected in the Yangtze River Estuary Underdeveloped Delta shows that there is a clear maximum accumulation peak in the 137Cs section of the Yangtze River Estuary, corresponding to the 137Cs scattered sedimentation in 1963. The coexistence of 137Cs in the section corresponds to 1959 From 1959 to 1964, the average sedimentation rate of the Yangtze River subaqueous delta was 2.4-4.8 cm / a, and it was reduced to 1.4-1.8 cm / a from 1964-2006. It shows that the overall siltation rate in the Yangtze River Estuary Sub-Delta has been greatly reduced, probably due to the drastic reduction of sediment yield and sediment in the basin due to the impoundment of the Three Gorges Project. Although the reduction rate of siltation rate is different across the Yangtze River subaqueous delta, the reduction rate is very fast, indicating that significant changes have taken place in the development of the Yangtze River Delta. Erosion has been observed in some parts of the submarine delta region.