Holocene palaeoflood events recorded by slackwater deposits along the Jin-shan Gorges of the middle Yellow River, China

Abstract

Palaeoflood slackwater deposits (SWDs) are the natural record of overbank flooding and are often found within aeolian loess-soil profiles along the river valleys of the middle Yellow River basin. Palaeo-hydrological field investigation was carried out along the Jin-shan Gorges of the middle Yellow River after the great flood in 2012. We founded the new palaeoflood SWDs profile (YHG-B) on the basis of previous results in the YHG site, and collected the 2012 flood slackwater deposits. Analytical results, including magnetic susceptibility and particle size distribution, which is similar to the flood SWDs in 2012, indicate that these well-sorted palaeoflood SWD beds were deposited from the suspended sediment load in floodwaters. They have recorded the extraordinary palaeoflood events which occurred between 3200 and 3000 a BP as dated by the optically stimulated luminescence method in combination with pedo-stratigraphic correlations with the previously studied Holocene pedo-stratigraphy in the Yellow River drainage basin. According to the palaeoflood peak stages indicated by YHG-A and YHG-B, the peak discharges of these palaeoflood events vary in a range from 28 340 to 48 410 m3/s by using HEC-RAS one dimensional model. This discharges result error is less than 5% with previous published discharges by using Slop-Area method in 2012. The extraordinary flood events were documented not only on the Yellow River, but also on its tributaries such as the Weihe River, the Jinghe River, and the Qishuihe River. The flooding events are therefore considered to be a regional expression of known climatic events in the northern hemisphere and demonstrate Holocene climate was far from stable. This work will increase our understanding of the interactions between fluvial environment and climatic change in the semi-arid and sub-humid regions, and provide information that is useful for interpretation and calibration of the modern short-term gauged records.