Late Pleistocene and Holocene extreme hydrological event records from slackwater flood deposits of theAnkang east reach in the upperHanjiangRiver valley,China

Abstract

This paper reports an investigation into palaeoflooding along the upper reaches of the Hanjiang River valley, China. Based on the sedimentary evidence of the palaeohydrological regime, two bedsets of palaeoflood slackwater deposits (SWDs) were identified interbedded within the Holocene loess–soil sequence along the riverbanks of the Ankang east reach. Optical Stimulated Luminescence (OSL) dating and stratigraphical correlation with previously dated sites were used to reconstruct the chronology of the palaeoflood events. The results show that the palaeoflood events represented bySWD1 occurred between 13 000 and 12 400 a, coincident with the climatic transition from the Bølling–Allerød (BL+AL) stage to the Younger Dryas (YD) event. The palaeoflood events recorded bySWD2 were dated to 1000–800 a, corresponding to the later stages of the North Song Dynasty (AD960–1127) and the subsequent South Song Dynasty (AD1127–1279), which was a time of climatic decline according to historical documents. Palaeoflood discharges were estimated using the step‐backwater method, and the peak discharges were estimated to be in the range 35 200–47 400 m3 s−1. These results are of significance to our understanding of the regional hydrological response to global climatic change, the utilization of water resources, hydraulic engineering, flood control and disaster reduction.