Sedimentary records of palaeofloods in the Wubu Reach along the Jin-Shaan gorges of the middle Yellow River, China

The Yellow River is known for the heavy suspended sediment load resulting from intensive soil erosion and human disturbance in the drainage basin. Palaeohydrological investigations were carried out along the Jin-Shaan gorges in the middle reaches of the Yellow River. A set of palaeoflood slackwater deposits (SWDs) were identified interbedded in the Holocene loess-soil sequence within the cliff riverbanks. Analytical results of magnetic susceptibility and particle-size distribution indicate that these well-sorted palaeoflood SWD beds were deposited by the suspended sediment load of the floodwater sourced from the loess tablelands in the middle reaches of the Yellow River. Four episodes of extraordinary palaeoflood events have been recorded in the Lianghekou (LHK) site. These hydro-climatic events were dated to 3200-2900 a by using the optically stimulated luminescence (OSL) method in combination with pedo-stratigraphic correlations with the previously studied Holocene pedo-stratigraphy (YHG site) in the Yellow River drainage basin. The peak discharges were estimated to be 41,268-47,415 m3 s−1 by using the slope-area method of streamflow measurement. They are about twice the largest gauged flood (24,000 m3 s−1) that has ever been measured in the Wubu gauge station. These extraordinary palaeoflood events are correlated with Holocene climatic variability characterized by cooling and drying during the period 3200-2900 a. This study provides sdata for hydraulic engineering, development of water resources and mitigating flood hazard in the Yellow River drainage basin, and also gives insight into understanding the sensitivity of regional hydro-climatic systems and the effects of climate change.