废黄河三角洲的演变

THE DEVELOPMENT OF THE ABANDONED YELLOW RIVER DELTA

本文主要根据历史文献,论述1194～1855年的古黄河口泥沙堆积形式、速率及其沉积特点,并探讨了废黄河三角洲形成机理和类型,以及尾闾变迁对下游河道的影响。认为在黄河南流夺准入黄海过程中,河口和三角洲发育具有明显的阶段性;前、后两期形成不同类型的三角洲,前期为径流一潮汐型,后期转化为径流一波浪型;后期河口迅速延伸,河口基准面相对抬升所引起的溯源淤积可达河南境内。

According to relevant historical documents, the paper studies the character and the changing rate of sedimentation at the ancient Yellow River estuary from 1194 to 1855 A.D.,the forming mechanism and the types of the abandoned Yellow River Delta, and its effects on lower reaches. Based on the above studies, it can be summed up in the following aspects.1. On the basis of the changes of hydrological conditions, silt content and human activities, the evolutionary processes of the abandoned Yellow River Delta can be distinguished into two stages. In the early stage(1194-1494 A.D.) only a part of the discharge of the Yellow River flowed southward into the Huaihe River and a small amount of silts deposited on the mouth, therefore, the developing rate of the ancient delta was very slow. Judging from the loudspeaker-shaped estuary. the early abandoned Yellow River Delta belonged to runoff-tidal typal delta. In the later stage, as all the discharge of the Yellow River flowed into the Huaihe, the silts deposited rapidly on the mouth region, and formed bird-bill-shaped delta. In the light of the delta shape in the later stage, it can be interred that the hydrodynamic of water acting on the front edge of delta was mainly runoff and waves, the ridges of tidal current developed outside the mouth region, therefore, the delta was regarded as the run-offwave typal delta.2. Because of the extension of the abandoned Yellow River estuary in the later stage, the base level of erosion rose relatively, it Ied up to the headward depositions, which might reach to Henan province.3. The abandoned Yellow River Delta expanded rapidly since 1494 A.D., especially after 1578 A.D..It is related to the physical environment of the whole area and the increasing human activities, especially to cold climate period during 17-19 centuries and human activities since middle Ming Dynasty.