汉江上游郧西段全新世古洪水水文学研究

Hydrological study on holocene palaeoflood at Yunxi section of upper reaches of Hanjiang River

通过对汉江上游的考察,在郧西段归仙河口(GXHK)发现了典型的全新世古洪水滞流沉积剖面。采集滞流沉积层样品,进行粒度、磁化率等分析,证明研究地点具有典型的古洪水滞流沉积层。通过地层学对比分析,确定两次古洪水事件分别发生在3 000-2 700 aB.P.和公元100-200年(即1 850-1 750 aB.P.)。利用沉积学、水文学方法计算出GXHK的古洪水流量介于63 090～64 320 m3/s之间。用2010年、2011年大洪水洪痕的现代水文学验证和美国学者Baker提出的河流流域面积与大洪水洪峰流量关系进行对比分析,证明古洪水水文学计算结果合理可靠,从而为汉江上游的工程建设及沿岸地区的防洪减灾提供参考。

Through field investigation in the upper reaches of the Hanjiang River,palaeoflood slackwater deposit was found in the GXHK reach of Yunxi county.With the evidences from the collected samples of the slackwater deposits and the analysis of the grain size distribution,the magnetic susceptibility and so on,it can be seen that the slackwater deposits present typical palaeoflood study area.By pedo-stratigraphical contrast analysis,it is confirmed that the two palaeoflood events be dated back to 3 000-2 700 a B.P.and 1 850-1 750 a B.P.respectively.By using the sedimentological and hydrological methods,the palaeoflood peak discharge was calculated at 63 090-64 320 m3/s in the GXHK reach.With the modern hydrology of deluge floodmark in 2010,2011 and the relationship between drainage area and peak discharge proposed by American scholar V.R.Baker,contrast analyses were carried out,which shows that,the calculation results were reasonable and reliable.The method can provide a reference to engineering construction,flood control and disaster reduction in the upper reaches of the Hanjiang River.