Scraping Effect of Dam-Overtopping Debris Flow—A Case Study of Chutou Gully ‘8.20’ in Miansi Town, Wenchuan County

ABSTRACT

After the May 12 earthquake in Wenchuan, numerous debris flow disasters occurred due to heavy rainfall. After the earthquake, disaster prevention and mitigation projects, such as the sand dam, played an essential role in safety. However, when the outflow of solid material exceeds the designed storage capacity of the sand dam, the debris flow overtopping the dam intensifies the scraping effect on the source material of the gully channel. This paper takes the ”8.20” debris flow in the Chutou gully as the research object. A transport mode of the debris flow after dam overtopping is studied through comprehensive field investigation, theoretical analysis, and indoor model tests. A quantitative evaluation model is established for the scraping depth and scraping volume of dam-overtopping debris flow. The study results showed that once the debris flow overtops a dam, the loose source carried by the channel is involved in the entire migration process, enlarging the fluid scale and intensifying the damage along the channel. The results agree with the measurements and observations, with maximum relative errors of 5.81% and 14.70%, respectively. This shows model validity. Furthermore, the test results show that the debris flow scarping phenomenon in the γ=[1.4 t/m³, 1.6 t/m³] interval is the most significant. Overall, this study will help improve future engineering decisions, design strategies, and finding the best design solutions to minimize the risk of dam-overtopping debris flow disasters.

KEYWORDS:

• Chutou gully
• dam-overtopping debris flow
• scraping effect
• section flow method
• model test

Acknowledgments

Thank Professor Shu-jun Tian for his constructive comments, Mr. Cheng-zhuang Gu for his remote sensing image data, and Professor Xiao-yi Fan for his technical support for data post-processing. We would like to thank MogoEdit (https://www.mogoedit.com) for its English editing during the preparation of this manuscript.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Author Contribution

Chen Huang: Writing-original draft, Methodology, Software, Data curation. Qijun Hu: Conceptualization, Supervision. Mingyang Li: Visualization, Investigation.

Additional information

Funding

This research was financially supported by the National Natural Science Foundation of China [Grant No. 52178357], 2020 Tianfu Technology Elite Project, Tianfu 10000 Talents Program of Sichuan Province [No. 658], and the Science and Technology Innovation Base (platform) Project of Education Department of Sichuan Province [Grant No. 22CXTD0087].