三角洲废弃河道演化过程及受控机制——以黄河刁口废弃河道为例

废弃河道是河流系统的重要组成部分,其沉积记录蕴含了丰富的流域内构造活动、水文特征、海平面波动等环境变化的珍贵记录。然而相比内陆河废弃河道,三角洲废弃河道的演化过程及机制研究尚显不足。1976年黄河人工改道清水沟流路,切断了刁口流路的河流水沙供给,刁口流路逐渐废弃。通过1976—2016年的Landsat遥感影像、黄河水下三角洲测深资料和刁口流路河道高程测量数据,探讨了黄河刁口流路废弃河道演化过程及其受控机制。结果表明,刁口流路废弃40年来,河口不断向岸蚀退,河道长度逐渐萎缩,但废弃河道沉积过程并未完全中止,刁口流路L7—L11河段每年约有10×10⁴ t泥沙不断充填废弃河道,河道主槽高程抬升0.3~2.0 m。海洋动力是废弃河道演化的关键动力机制,波浪对刁口流路三角洲的冲刷为废弃河道充填提供了重要的物源,潮流携带悬浮泥沙回溯废弃河道,为其提供了直接泥沙供给。

Evolution of abandoned deltaic river channel-A case from the Diaokou channel of the Yellow River

Abandoned channels are one of the major components of a deltaic system,which contains valuable information related to tectonism,hydrology,sea-level fluctuation and environmental changes of the catchment.Comparing to the study of filling process of abandoned channels on land,which are well studied in the past decades,little research has been devoted to the tidal-dominated abandoned channels.The Diaokou River channel was fully abandoned in 1976 by an artificial construction separating it from the main course of the Yellow River.With the support of landsat images,bathymetric surveys and elevation data of the abandoned Diaokou River channel,the evolution of this tide-dominated abandoned channel is documented in this study.Since abandonment,about 0.3~2.0 meters of filling sediment have deposited in the channel,with along-channel and landward decrease in sedimentation.Marine dynamics is the main force to control the evolution of abandoned channels.The severe erosion near the abandoned channel mouth,as a source of sediments,has made the channel shortening gradually.