Quantitative analysis of artificial dam failure effects on debris flows - A case study of the Zhouqu '8.8' debris flow in northwestern China

Yan Chong; Guan Chen; Xingmin Meng; Yunpeng Yang; Wei Shi; Shiqiang Bian; Yi Zhang; Dongxia Yue

doi:10.1016/j.scitotenv.2021.148439

Quantitative analysis of artificial dam failure effects on debris flows - A case study of the Zhouqu '8.8' debris flow in northwestern China

Sci Total Environ. 2021 Oct 20:792:148439. doi: 10.1016/j.scitotenv.2021.148439. Epub 2021 Jun 11.

Authors

Yan Chong¹, Guan Chen², Xingmin Meng¹, Yunpeng Yang¹, Wei Shi¹, Shiqiang Bian¹, Yi Zhang¹, Dongxia Yue³

Affiliations

¹ MOE Key Laboratory of Western China's Environmental Systems, School of Earth Sciences, Lanzhou University, Lanzhou 730000, P. R. China; Technology & Innovation Centre for Environmental Geology and Geohazards Prevention, School of Earth Sciences, Lanzhou University, Lanzhou 730000, P. R. China.
² MOE Key Laboratory of Western China's Environmental Systems, School of Earth Sciences, Lanzhou University, Lanzhou 730000, P. R. China; Technology & Innovation Centre for Environmental Geology and Geohazards Prevention, School of Earth Sciences, Lanzhou University, Lanzhou 730000, P. R. China. Electronic address: gchen@lzu.edu.cn.
³ Technology & Innovation Centre for Environmental Geology and Geohazards Prevention, School of Earth Sciences, Lanzhou University, Lanzhou 730000, P. R. China; College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, P. R. China.

PMID: 34147790
DOI: 10.1016/j.scitotenv.2021.148439

Abstract

Artificial dams are one of the most common hydraulic structures for mitigating debris flow disasters in alpine valley regions. However, performance alteration and failure after successive debris flows can lead to dam failure, releasing large amounts of materials within a very short time; moreover, the contribution of artificial dam failures to debris flows is poorly understood. This study quantitatively analyzed the artificial dam failure effects based on the numerical simulations of the Zhouqu '8.8' debris flow, with three scenarios: all nine dams failed (S1); no dams were ever built (S2); all nine dams remained intact (S3). The results showed that artificial dam failures had a significant amplifying effect on the magnitude of a debris flow. The maximum velocity and flow depth decreased by 20% and 11.2% if all the dams did not collapse; comparison of S1 and S2 showed that discharge and velocity at the front of the debris flow increased by 54.6% and 89%, the bulk density and yield stress increased by 3.3% and 5.7%, due to artificial dam failures. This could increase the destructive capacity of a debris flow and the possibility of a river blockage. A single artificial dam failure could locally amplify the magnitude of debris flow. Overall, on the catchment scale, the magnitude of a debris flow was dominated by topography and channel geometry, which can reduce the amplification effect of dam failures at locations where the channel was curved. However, where the channel was straight and flat, the flow velocity and discharge increased cumulatively by 3 m/s and 637 m³/s due to cascading failure. In addition, a comprehensive scheme combining ecological and engineering measures to mitigate debris flow disasters is discussed. This quantitative study is important and urgent needed to understand the amplification effect of dam failures and to implement debris flow mitigation in alpine valley regions.

Keywords: Amplification effects; Artificial dams; Cascading failure; Dynamic processes; Zhouqu debris flow.

MeSH terms

China
Disasters*
Engineering
Rivers*