黄河上游靖远—景泰段全新世古洪水水文学

Palaeoflood Hydrological Reconstruction in JingyuanJingtai Reach in Upper Yellow River Valley

对黄河上游靖远—景泰段峡谷进行系统野外考察,在靖远县金坪村(JPC)发现典型的全新世古洪水滞流沉积物。通过光释光(OSL)测年和与黄河吉县段FJJ剖面进行地层对比,确定这期特大古洪水事件发生在3 200~3 000aB.P.,即全新世中期—晚期气候恶化转折阶段,对应着我国历史上商末至西周早期。采用古洪水水文学方法恢复古洪水洪峰水位,并且采用比降-面积法计算这一期多次古洪水事件的洪峰流量为16 110~17 740m3/s。同时,根据野外调查获得2012年7月31日黄河上游大洪水的洪痕高程,采用相同参数和方法恢复其洪峰流量,误差仅有2.7%,表明在该河段对于古洪水水文恢复计算参数选取和计算结果是可靠的。

A systematical field investigation is carried out in the upper Yellow River valley from Jingtai to Jingyuan reach .Palaeoflood slackwater deposits (SWD) are identified at several sites .The Holocene sediment profile at the site of Jinpingcun (JPC) is chosen for a further study on the palaeoflood hydrology .OSL dating and stratigraphic correlation with Jixian (FJJ) site in the middle reach gorge of the Yellow River show that these extreme palaeoflood events occurred during 3 200 3 000 a B .P .,at the time when the climate was at the turn from the Middle Holocene climatic optimum to the Late Holocene dry period .This corresponds to the transition period from Shang Dynasty to Western Zhou Dynasty when many serious drought and flood disasters , harvest failures , and major social changes occurred . The palaeoflood stage is obtained by palaeohydrological methods . The reconstructed palaeoflood peak discharges were 16 110 17 740 m 3 /s using the slope‐area method .Reconstruction of current flood (in 2012 .07 .31) and comparison with the gauged discharge prove that the hydrological method and hydrological parameters used are reliable .These results are very important to establish the relationship between peak discharge and occurrence frequency by 10 000‐year time‐scale in Lanzhou to Jingyuan reach .The method is very useful in Hydraulic engineering along the upper Yellow River .