Delta response to decline in sediment supply from the Yangtze River: evidence of the recent four decades and expectations for the next half-century
Delta response to decline in sediment supply from the Yangtze River: evidence of the recent four decades and expectations for the next half-century
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DOI：
10.1016/s0272-7714(02)00409-2
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发表时间：
2003-07
影响因子：
2.8
通讯作者：
Shi-lun Yang;I. Belkin;A. I. Belkina;Q. Y. Zhao-;Jianrong Zhu;P. Ding
中科院分区：
文献类型：
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作者：
Shi-lun Yang;I. Belkin;A. I. Belkina;Q. Y. Zhao-;Jianrong Zhu;P. Ding
为了研究长江三角洲对近几十年来长江来沙减少的响应，分析了长江水下三角洲1958~1997年的水深图，并结合同期的河流泥沙资料进行了分析。研究区的净淤积速率从1958年的38 mm/a下降到1978-1997年的8 mm/a，同期河流输沙量从466×106 t/a下降到394×106 t/a，含沙量从0.543 kg/m~3下降到0.448 kg/m~3。与内水下三角洲相比，外水下三角洲对河流泥沙负荷的下降更为敏感。从1958-1978年到1978-1997年，外水下三角洲的净增长速率从51 mm/年下降到2 mm/年，内水下三角洲的净增长速率从25 mm/年下降到14 mm/年。由于三角洲输沙量没有减少，淤积速率的下降速度比河流输沙速度更快。提出了区分三角洲进退的河流输沙临界门槛的概念。虽然这个临界值被发现在时间和空间上发生变化，但它对预测未来的增量响应是有帮助的。在人类活动，特别是三峡工程的影响下，未来50年，河流输沙量将降至临界值以下。这将导致三角洲整体后退取代三角洲进积；衰退将首先发生在外部水下三角洲。
In order to examine the delta response to decline in sediment supply from the Yangtze River during the recent decades, bathymetric maps of the Yangtze subaqueous delta surveyed from 1958 to 1997 were analyzed together with the river sediment dataset of the same period. The net accretion rate over the study area decreased from 38mm/yr in 1958–1978 to 8mm/yr in 1978–1997, while the river sediment discharge decreased from 466×106to 394×106t/yr and the suspended sediment concentration decreased from 0.543 to 0.448kg/m3during the same periods, respectively. The outer subaqueous delta is more sensitive to decline in river sediment load in contrast with the inner subaqueous delta. From 1958–1978 to 1978–1997, the net accretion rate decreased from 51 to 2mm/yr in the outer subaqueous delta and from 25 to 14mm/yr in the inner subaqueous delta. The accretion rate decreased more rapidly than the river sediment discharge because the amount of sediment transported out of the delta has not decreased. A concept of the critical threshold of river sediment discharge that separates delta progradation from recession is proposed. Although this critical value was found to change temporally and spatially, it was instrumental in predicting the future delta response. Under the impacts of human activities, particularly, the Three Gorges Dam Project, the river sediment load would be reduced below the critical value during the next five decades. This would result in a general delta recession replacing delta progradation; the recession would occur first in the outer subaqueous delta.