长江中游泥沙淤积与全新世长江三角洲的发育——兼论长江中游防洪策略

Sediment Deposition in the Middle Reaches of the Yangtze River and the Development of the Yangtze River Delta in the Holocene:A Discuss on Flood Control Strategies in the Middle Reaches of the Yangtze River

全新世海侵以来,巨量泥沙在长江河口湾一带堆积,形成了自西向东雁列的六个亚三角洲河口沙坝。长江口随之从镇江、扬州向东南方向推进到长兴岛一带,加之百余年来长江中游荆江河曲的演化和簰洲湾弯曲河道的发展,长江中下游河道累计延长620 km。长江中下游河床纵比降的自动调整,促使了中游一带河道泥沙淤积达12.9 m。长江河道的不断延伸加长和长江中下游冲积河床对纵比降的自动调整,是长江中游河道淤涨和洪水位上升的内因;而荆江一带人类工程活动的参与,强化了长江泥沙向下游输移,加速了长江三角洲的发展和长江河道的延伸,构成了长江中游河道淤涨和洪水位上升的正反馈机制。长江中游防洪减灾策略、长江流域防洪规划和流域国土空间规划,应统筹考虑长江口浚海清淤和长江三角洲泥沙资源化利用,或开辟新的防洪入海通道,如开辟南通-如东入海新运河暨防洪新河。

Since the Holocene transgression,a huge amount of sediment has accumulated in the Yangtze estuary,forming six subdelta estuarine bars from west to east.The estuary of the Yangtze River has also advanced southeast from Zhenjiang and Yangzhou to Changxing island.Coupled with the evolution and development of the Jingjiang and Paizhou bay meanders in the middle reaches of the Yangtze River over the past hundred years,the riverway of middle and lower reaches of the Yangtze River have extended 620 km in total.The automatic adjustment of the longitudinal slope of the riverbed in the middle and lower reaches of the Yangtze River resulted in 12.9 meters of sediment deposition in the middle reaches of the river.The continuous extension and lengthening of the Yangtze River channel and the automatic adjustment of the longitudinal slope of the alluvial riverbed in the middle and lower reaches of the Yangtze River are the internal causes of the silting and flood level rise in the middle reaches of the Yangtze River.The participation of human activities in the Jingjiang River strengthened the sediment transport downstream of the Yangtze River,accelerated the development of the Yangtze River delta and the extension of the river channel,and constituted a positive feedback mechanism of channel silting and flood level rise in the middle reaches of the river.Flood prevention and disaster reduction strategies for the middle reaches of the Yangtze River,flood control planning and territorial spatial planning should consider the dredging and desilting of the Yangtze Estuary and the utilization of sediment resources in the Yangtze River Delt,or opening up new flood control channels into the sea,such as the Nantong-Rudong new canal into the sea and new river for flood control.