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通过对汉江上游河谷开展广泛细致的野外考察,在汉江上游旬阳西段全新世黄土-土壤剖面发现四层典型的古洪水滞流沉积物。对于系统采集的样品,进行粒度成分、磁化率分析,从沉积学角度证明了它们是典型的古洪水滞流沉积物。这些古洪水滞流沉积层夹在全新世风成黄土-土壤地层序列中,其每一层古洪水滞流沉积物记录了一期古洪水事件。根据OSL测年数据,并结合考古年代学和典型剖面地层对比,确定了这四期古洪水事件分别发生在8 500~8 400 a B.P.、4 200~4 000 a B.P.、3 200~2 800 a B.P.和1 800~1 700 a B.P.。利用古洪水SWD尖灭点高程法,恢复了这四期古洪水洪峰水位,介于233.0~239.2 m之间;进而基于HEC-RAS模型重建了四期古洪水洪峰流量,介于26 500~46 800 m3/s之间。将古洪水研究成果加入后,得到了远超过实测洪水和历史洪水重现期的稀遇洪水的水文信息,延长了汉江上游安康-旬阳段流域洪水的数据序列至万年尺度,使洪峰流量-频率曲线的稀遇洪水部分有了点据控制,百年和千年一遇的洪水洪峰流量的计算由外延变为内插,提高了设计洪水的精度。并且通过古洪水水文计算得到,该河段万年一遇洪水洪峰流量为46 900 m~3/s,千年一遇洪水洪峰流量为37 800 m3/s,百年一遇洪水洪峰流量为28 900 m~3/s。这对于汉江上游水利工程、防洪工程和城镇建设的洪水设计提供了十分重要基础数据。
Through extensive and careful field investigation of the upper reaches of the Hanjiang River, four typical paleo-flood stagnant sediments have been found in the loess-soil profile of the Holocene in the western Xunyang part of the Hanjiang River. For the samples collected by the system, the grain size composition and magnetic susceptibility were analyzed, and sedimentology proved that they are typical paleo-flood stagnant sediments. These pale flood stagnant sediments are trapped in the sequence of Holocene aeolian loess-soil stratigraphy, each of which contains an ancient flood event. According to the OSL dating data and the comparison of archeological chronology and typical section stratigraphy, it is confirmed that the four ancient flood events occurred in 8 500 ~ 8 400 a BP, 4 200 ~ 4 000 a BP, 3 200 ~ 2 800 a BP and 1 800 ~ 1 700 a BP. Based on the HED-RAS model, the flood peak flood discharge of the four periods was reconstructed from 26 500 to 46 800 m3 / s. After adding the research achievements of paleo-floods, hydrological information was obtained which far exceeded the rare floods of measured floods and historical floods, prolonging the data sequence of flood in Ankang-Xunyang Drainage Basin up to the 10,000-year scale, - The rarefied flood part of the frequency curve is controlled by some points. The calculation of flood peak flow in a century and a thousand years changes from epitaxial to interpolation, which improves the accuracy of design flood. It is also calculated from the paleo-hydrological hydrology data. The flood peak flow of this section is 46 900 m 3 / s in every 1000 years, 37 800 m 3 / s in the once-in-the-millennium flood and 28 900 m ~ 3 / s. This provides very important basic data for flood design of water conservancy projects, flood control projects and urban construction in the upper reaches of the Han River.