Hydrological studies of the historical and palaeoflood events on the middle Yihe River, China

• Historical and palaeoflood slackwater deposits were identified in the middle Yihe River.
• Peak discharges of these palaeoflood events were estimated to be 12,300–15,310 m3/s.
• They were dated to 3100–3000, 1800–1700, 700–550 and 350–250 a B.P. using OSL method.
• These events are linked to anomalous monsoonal climatic change over East Asia.

Palaeo–hydrological and sedimentary investigations were carried out in the Longmenxia Gorge of the middle Yihe River. Five bedsets of flood slackwater deposits (SWD) were found interbedded into Holocene aeolian loess–soil profiles in the river bank at the Longmenxia site. They were identified as the deposits of the suspended sediment load during the extreme flood events of the Holocene. The minimum flood peak discharges were estimated to be 12, 300–15, 300 m3/s using the slope–area method. These are about twice the largest gauged record (7180 m3/s) that has occurred since 1937. These flood events occurred at 3100–3000 a B.P., 1800–1700 a B.P., 700–550 a B.P. and 350–250 a B.P., as dated by optically stimulated luminescence (OSL) in combination with stratigraphic correlation, to which may be added the recorded events of the 223 and 1761 CE floods. These were associated with Holocene monsoonal shifts and abrupt climatic events. This research not only provides palaeoflood discharge estimates on the middle Yihe River, but also provides important data for understanding interactions between regional hydro–climatic systems and global climate change in humid and semi–humid monsoonal regions, such as China.