Paleoflood evidence for an upper limit of the maximum flood magnitudes along the Gold Gorge, the upper Hanjiang River, China

This paper provides an important archive of the largest paleoflood event along the Gold Gorge of the upper Hanjiang River, with a review of regional extraordinary flood magnitudes using historical, gauged, and paleoflood datasets. Paleoflood slackwater deposit (SWD) was identified using the sedimentological criteria and highresolution physicochemical indexes. End-member model demonstrates the paleoflood SWD was dominated by sand component. Optical chronology indicates the paleoflood event was dated to 1000-900 a BP, corresponding to the North Song Dynasty (AD 960-1127). Paleoflood magnitudes derived from one-dimensional unsteady model vary between 23,000 and 34,000 m3/s. The paleoflood data provide a good representation of extraordinary flood event with a 10,000-years return period and greatly improve current flood frequency estimations. Moreover, the envelope curve for extraordinary floods was first established as Q = 50D0.65 and the paleoflood peak discharges are approximately 2-2.5 times of the largest gauged floods within the catchment. These results provide an upper limit of the maximum flood magnitudes along the upper Hanjiang River and also expand our understanding of rare and large magnitude floods in the middle Yangtze River valley.

Automated summary

This paper presents an important archive of the largest paleoflood event in the Gold Gorge of the upper Hanjiang River. The study uses historical, gauged, and paleoflood datasets to analyze the flood magnitudes and improve flood frequency estimations. The results show that the paleoflood event occurred 1000-900 years ago during the North Song Dynasty, with a magnitude between 23,000 and 34,000 m3/s. The findings provide valuable information for understanding the maximum flood magnitudes in the upper Hanjiang River and contribute to the knowledge of rare and large floods in the middle Yangtze River valley.