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通过对黄河中游北洛河的野外考察,在宜君基岩峡谷全新世风成黄土-土壤剖面中发现三层古洪水滞流沉积物(SWD).野外观察和室内实验分析,证明它们是北洛河特大洪水悬移质泥沙在高水位滞流环境下的沉积物.这些古洪水滞流沉积层夹在全新世中期古土壤之内,其每一层记录了一期特大洪水事件.利用古水文学方法恢复了古洪水洪峰水位和流量,确定三期古洪水的洪峰流量介于13600-14100 m3/s之间.这就将北洛河中游洪水数据序列延长到万年尺度,为更加精确地建立洪峰流量-频率关系奠定了基础.这些结果对北洛河流域水利工程建设和防洪减灾提供了可靠依据.根据土壤地层和气候地层对比,结合OSL测年数据,确定这三期古洪水的发生年代为8000-7800 aBP(SWD1),6000-5000aBP(SWD2)和4200-4000 aBP(SWD3).它们与全新世大暖期三个气候突变事件密切相关,是气候不稳定状态下,区域水文系统极端性变化的重要表现.这就为深入理解全球变化对于半干旱地区气候水文系统的影响提供了新的证据.
Through the field investigation of the Beiluohe River in the middle reaches of the Yellow River, three layers of pale flood stagnate sediments (SWDs) were found in the Holocene aeolian loess-soil profile in the Yijun rocky canyon.The field observations and laboratory experiments show that they are North Luo Sediments of suspended sediment suspended in the high water level in the vast floods of the river, which are trapped in the mid-Holocene paleosol and each of which record a major flood event, The hydrological method restores the ancient flood crest level and the flow rate, and determines that the flood peak flow of the three ancient flood waters is between 13600-14100 m3 / s, which extends the sequence of the flood data in the middle reaches of the Beiluohe River to a multi-year scale, To establish the peak flow-frequency relationship, which laid a solid foundation for the construction of water conservancy projects and flood control and disaster mitigation in the Beiluohe River Basin.According to the comparison of soil strata and climate stratigraphy, combined with the OSL dating data to determine the three ancient floods The occurrence ages are 8000-7800 aBP (SWD1), 6000-5000aBP (SWD2) and 4200-4000 aBP (SWD3), which are closely related to the three climatic abrupt events of the Holocene.They are characterized by regional water Department of Literature Important manifestation of extreme change. This is in-depth understanding of the global impact of climate change on the hydrological system of semi-arid areas provides new evidence.