黄河中游土壤侵蚀与下游古河道三角洲演化的过程响应

Research on the Relationship of Loess Plataeu Soil Erosion to the Evolution of Yellow River Delta Since the Late Pleistocene

根据黄土高原土壤侵蚀的周期特点 ,结合华北平原古河道、古三角洲的演化过程 ,应用泥沙输移的过程响应 ,分析了晚更新世以来黄河中游黄土高原土壤侵蚀与下游古河道、三角洲演化的关系。在人类历史之前 ,黄土高原土壤侵蚀基本上遵循自然生态环境演化规律 ,强烈侵蚀期发生在干冷向温湿气候转化的过渡期 ,在强烈侵蚀的初期是古河道形成期 ,强烈侵蚀的中期是三角洲进积期 ,黄河下游河流改道、三角洲横向扩展发生在强烈侵蚀的衰退期。人类历史时期 ,土壤侵蚀的外营力迭加了人为作用 ,破坏了地质历史时期的规律性 ,土壤侵蚀强度越来越强 ,基本上按照旱涝变化频率而演化。干冷期降雨不均匀系数增加 ,土壤侵蚀加重 ,径流量较少 ,河床以淤积为主 ,是古河道形成期 ;正常年黄河泥沙输移比接近于一 ,是三角洲进积期 ,温湿期降雨量增加、径流量加大 ,下游河流改道 ,三角洲横向发展。

The Yellow River has been an integrated drainage system since it linked up in the middle pleistocene Serious soil erosion of Loess Plateau in the middle reaches has caused the river bed deposition in the lower reaches and the delta change in river outlet It is the main reason that sediment content in the Yellow River has occupied first place in the world rivers In the late Pleistocene and early and middle Holocene epoch period, Loess Plateau soil erosion law basically abided by the law of natural ecological environment evolution Intense soil erosion main occurred in the transition period between loess accumulation and soil formation on the base of polycyclic climatic variation Palaeochannels of the Yellow River lower reaches main developed in the early period of intense soil erosion The middle period of intense soil erosion was river outlet delta development period Lower reaches river diversion centralizing happended in the late period of intense soil erosion In the human history period, as the development of human history, soil erosion continuative occurred and soil erosion intensity became more and more serious because human irrational action destroyed natural vegetation and accelerated soil erosion Loess Plateau soil erosion evolution law basically abided by the frequently of changes between drought and excessive rain. In arid period, rainfall was not fairly well distributed, and the calamity of drought and excessive rain became frequent, soil erosion became more serious However, amount of runoff were less, river bed were silted up, and palaeochannels developed In the year of rainfall being fairly well distributed, the Yellow River sediment content and delivery ratio were close to one, the deposited velocity of river outlet delta increased In the warm and humid period, runoff content increased, lower reach river diversion frequency became higher and higher, river outlet delta developed in transverse