Debris flow entrainment rates in non-uniform channels with convex and concave slopes

ABSTRACT

Channel topography plays an important role in debris flow entrainment processes. Field observations and flume experiments have demonstrated two notable erosion effects: abrasion on convex slopes resulting from layer-by-layer shearing and impact erosion on concave slopes. Most existing formulas for debris flow entrainment rates are derived from the uniform slope assumption and do not account for the two erosion effects. In order to take abrasion and impact erosion into consideration, this study incorporated two channel curvature functions into the entrainment formula that is based on equilibrium between flow frictional forces and basal resistance forces. The two functions control the effects of entrainment on different slope types and are based on empirical relationships with curvature obtained in flume experiments. The revised formula provides a unified procedure for debris flow entrainment rates in non-uniform channels.

Keywords:

• Concave slopes
• convex slopes
• debris flow
• entrainment
• impact erosion
• non-uniform channel

Acknowledgements

Jinbo Tang’s comments helped improve the experimental implementation. Flume experiments at the Dongchuan Debris Flow Observation and Research Station, Chinese Academy of Sciences, benefited from the participation of many people, especially Yong Hong, Zhaoning Yang, Jinheng Zhao, Yanji Li, Cheng Chen, Yuanhong Huang and Yuan Tao. The efforts of two anonymous reviewers are greatly appreciated as well.

ORCID

Pu Li http://orcid.org/0000-0003-0591-4007

Kaiheng Hu http://orcid.org/0000-0001-8114-5743

Xiekang Wang http://orcid.org/0000-0003-0065-404X

Additional information

Funding

The study was funded by the National Natural Science Foundation of China [grant number 41371039], the National Basic Research Program of China (973 Program) [grant number 2015CB452704] and the Open Foundation of State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University [ grant number SKHL1426].