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通过对汉江上游详尽的野外考察,在湖北郧县晏家棚河段全新世黄土—古土壤地层中发现3层典型古洪水滞流沉积物。在沉积学的基础上,使用OSL技术断代,确定3期特大洪水事件分别在1 000~900 a BP,1 800~1 600 a BP和3 200~2 800 a BP期间发生。采用“古洪水SWD尖灭点高程法”确定这3期古洪水事件的洪峰水位介于176.20~176.73 m。运用Arc GIS耦合HEC-RAS水力模型,推求这3期古洪水事件的洪峰流量介于53 770~55 950 m3/s,并从多种角度验证了该模型计算结果的科学性和合理性。将此结果与实测洪水和历史洪水资料接续,构成万年尺度洪水水文数据序列,得到汉江上游晏家棚河段万年一遇和千年一遇洪水的流量分别为59 100和45 200m3/s。采用HEC-RAS模型对研究河段进行古洪水模拟,方法科学,结果可靠。将该河段洪水水文数据序列有效地延长到万年尺度,极大地提高了设计洪水的可靠性。
Through detailed field investigation in the upper reaches of Hanjiang River, three layers of typical paleo-flood stagnant sediments were found in the Holocene loess-paleosol stratum in the Yanjiahedu section of Yun County, Hubei Province. On the basis of sedimentology, the use of OSL technology was discontinued to determine the occurrence of 3 extraordinary flood events occurring between 1 000-900 a BP, 1 800-1 600 a BP and 3 200-2 800 a BP respectively. Using the “ancient flood SWD cut-off point elevation method” to determine the flood events of these three flood events ranging from 176.20 ~ 176.73 m. By using Arc GIS coupled with HEC-RAS hydraulic model, the peak flow of these three flood events is estimated to be between 53 770 and 55 950 m3 / s, and the scientific and reasonable results of this model are verified from various perspectives. This result is connected with the measured flood and historical flood data to form flood hydrological data series on a multi-year scale. The flow rates of once-a-year and once-a-year floods in Yanjiazude reach reach 59,100 and 45,200m3 / s, respectively. The HEC-RAS model was used to simulate the flood in the study section, the method was scientific and the result was reliable. Extensively extending the sequence of flood hydrological data at the river reach to a multi-year scale greatly improves the reliability of design floods.