800年来苏北废黄河三角洲的演变模式

EVOLUTION OF THE ABANDONED HUANGHE(YELLOW) RIVER DELTA IN NORTH JIANGSU PROVINCE IN 800 YEARS

根据历史资料、数据和相关研究,结合研究区域背景,分析苏北废黄河三角洲的演变。结果显示,岸线演变在发育阶段和侵蚀阶段分别为向海延伸约90 km和侵蚀后退约22 km,面积相差约800 km2,三角洲地貌演变表现为岸线平直-曲折-平滑-平直的过程。在废三角洲陆海相互作用的基础上,运用演化模式分析三角洲的演变过程。该三角洲演变可以分为7个演变阶段,发育期在径流和潮流作用下以沙洲并陆淤积延伸方式进行,侵蚀期在波浪和潮流作用下以沙洲合并侵蚀后退和淤积外长交替侵蚀的方式。泥沙输运、人类活动和气候变化对废三角洲的演变有重要影响,巨量的来沙是三角洲发育的原因,泥沙平衡被打破是侵蚀的主要原因。发育期中,泥沙输运影响淤积速度和位置,人类活动和气候变化影响黄河河道迁移、输沙量和产沙量;侵蚀期中,泥沙输运影响侵蚀状态,人类活动在一定程度上影响海岸带冲/淤,气候变化将影响三角洲的演变趋势。

Based on historical information,we analyzed the evolution of the abandoned Huanghe(Yellow) River delta in 800 years.We divided the evolution into growth and erosion periods and seven phases.Shoreline extended seaward for about 90 km in the growth phase,and withdrew landward for 22 km in the erosion phase,making a difference of about 800 km2 in area.Geomorphology evolution of coastline experienced a course of straight–zigzag–smooth–straight in curvature because of land-sea interaction changes.In the growth period,the delta initiated from former shoals with siltation,deposition,and extended seaward in alternation of runoff-tide actions.In the erosion period,shoals re-occurred,was eroded back,and filled,in alternation of wave-tide actions.Sediment transport,human activities,and climate change contributed to the impact on the evolution of the delta.The huge amount of sand supply has been the key factor for the delta development,and sediment disbalance was the main reason of delta erosion.In the growth period,sediment transport affected the deposition velocity and location,and human activities and climate change affected the channel migration of the river course,and sediment discharge and supply.In the erosion period,sediment transport was less and slow,and human activities affected natural deposition-erosion along coastal zone to a certain degree.Climate change affects the evolution trend of the delta.