Geological study of an outburst flood event in the upper Yangtze River and risk of similar extreme events

• Published in: Global and planetary change Vol. 238; p. 104480
• Main Authors: Hu, Gang, Dong, Guanghui, Liu, Tao, Min, Rui, Yang, Zhijian, Gao, Qihui, Wang, Huiying, Wang, Ping, Chen, Jie, Zhang, Jiafu, Wang, Changsong, Zhao, Chaoying, Zhang, Aimin
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.07.2024; Elsevier
• Subjects: 14C dating; ENVIRONMENTAL SCIENCES; Hydropower stations; Outburst flood reconstruction; Yangtze River; Hydropower stations; 14C dating; Outburst flood reconstruction; Yangtze River
• ISSN: 0921-8181; 1872-6364
• DOI: 10.1016/j.gloplacha.2024.104480

Outburst flood sediments are studied on the upper course of the Yangtze River (known as the Jinsha River) where is a key region for the development of hydroelectric power. As the history and magnitude of outburst flooding in this stretch of the Jinsha River during historic times has remained largely undocumented, we have endeavored as part of this study to conduct field investigations into, and provide numerical dating (using OSL and 14C dating techniques) of outburst flood evidence found in the First Bend area of the Yangtze River. Carbonized nutshells and charcoal from the ancient settlement yielded 14C ages that precisely pinpointed an outburst flood event ∼1200–1300 cal yr BP, during China's Tang Dynasty (618–907 CE). However, OSL ages using the minimum age model for all outburst flood samples ranged from 9.1 to 1.8 ka, which was ∼0.5–7.8 ka older than the 14C-dated outburst flood. This discrepancy suggests a potential overestimation of quartz age when dating outburst flood sediments from the Holocene period. Furthermore, using 2D hydraulic modeling, we estimated the magnitude of the aforementioned outburst flood, revealing a reconstructed peak flow discharge of 51,000–55,300 m3/s. This discharge was three times greater than the 10,000-year flood for the hydroelectric power station nearest to the study area. Our study underscores the significant role of combining archaeological and geological evidence in enhancing paleoflood hydrology research. Through a multidisciplinary approach, our findings emphasize the importance of paleoflood hydrology studies in comprehending both the latent and catastrophic flood risks in alpine mountain areas amid the context of global warming. •A series of outburst flood sediments was identified in the First Bend area of the Yangtze River, with a maximum flood water surface ∼86 m high above modern river level.•The obtained 14C ages would suggest that the outburst flood occurred at ∼1200–1300 cal yr BP in the Tang Dynasty (618–907 CE) of China.•The reconstructed peak flow discharge (51,000–55,300 m3/s) is larger than the three times of the 10,000-yr flood for the nearest hydropower station to the study site. •Outburst floods were identified in the First Bend of the Yangtze River.•The 14C ages (∼1200–1300 cal yr BP) suggest the flood was in the Tang Dynasty.•The peak discharge is larger than triple the 10,000-flood of the nearest dam.