汉江上游黄坪村段东汉时期古洪水水文学研究

CATASTROPHIC PALAEOFLOOD STUDY IN HUANGPING SITE OF YUNXIAN COUNTRY IN UPPER REACHES OF HANJIANG RIVER

对汉江上游郧县黄坪村剖面的沉积学特征及所在河段地貌进行了研究。发现剖面中夹有典型古洪水沉积物，其记录了发生于19.0～1700aB．P的古洪水事件。根据水文学和沉积学原理，利用尖灭点法和SWD厚度与含沙量关系法恢复的古洪水行洪水位高程分别为154．95和156．85m，用比降法恢复的古洪水洪峰流量为65320和74442m^3／s。根据2011年汉江洪水洪峰痕迹高程用相同方法反推洪水流量，用Baker提出的河流流域面积与洪水洪峰流量关系进行了验证，证实所恢复的古洪水洪峰流量是合理的。

Hydrological investigations were carried out in the upper reaches of the Hanjiang River. The Huangping profile in the Hanjiang River Valley was found and observed ira detail in the field which contains a layer of palaeoflood slack-water deposits. The geomorphology and the parameters of the Huangping reach of Hanjiang River were measured in the field. The grain-size distribution was analyzed in laboratory. The result shows that the gray palaeoflood slack-water deposits inserted in the paleosoil were different from the loess and the paleosol. The palaeoflood slack-water deposits recorded a catastrophic floods events that might occur during the Eastern Han Dynasty （1 900- 1 700 a 13. P）. According to the theory of Sedimentology and Hydrology, using the palaeoflood SWD pinch out and SWD thick-sand content method, the palaeoflood water level elevation was found respectively for 154.95 m and 156.85 m; Its peak flow wasrestored by slope method, and the ancient flood peak flow was calculated respectively for 65 320 m^3/s and 74 442 m^3/s. These results were checked with various methods, which indicate the reconstructed peak discharge is reliable. These results are of great significance to exploit water resources and mitigate flood disasters of the upper reaches of Hanjiang River, at the same time, these results are of great significance to understand hydrological response to global climatic change.