TY - JOUR

T1 - A new approach for analyzing the velocity distribution of debris flows at typical cross-sections

AU - Han, Zheng

AU - Chen, Guangqi

AU - Li, Yange

AU - Xu, Linrong

AU - Zheng, Lu

AU - Zhang, Yingbing

N1 - Funding Information:
Acknowledgments This study has received financial support from Kyushu University Interdisciplinary Programs in Education and Projects in Research Development; JSPS KAKENHI Grant Number 22310113 and the Global Environment Research Found of Japan (S-8); and the National Natural Science Foundation of China (Grant No. 41272376, L. Xu). These financial supports are gratefully acknowledged. We also thank Mohammad Reza Ghulami for revising the manuscript. And we thank Dr. Glade and two anonymous reviewers for providing helpful comments and revisions on the earlier draft of this paper.

PY - 2014/11/1

Y1 - 2014/11/1

N2 - The asymmetrical distribution of debris-flow velocity in a cross-section has long been observed and is currently regarded as one of the most essential issues in debrisflow research. Due to a lack of quantitative models for the velocity distributions of debris flows, most studies consider only the mean velocity. However, to optimize countermeasure structures, to estimate the erosion rate, or to evaluate the constitutive equations for shear behavior, it is beneficial to know the velocity profile in a cross-section. In this paper, a generalized model of typical channel geometries (e.g., rectangular, trapezoid, or V-shape) is proposed. A description of the velocity distribution that optimizes the Manning–Strickler velocity equation for transverse distribution and Egashira’s velocity equation for vertical distribution is presented; thus, the debris-flow velocity at any point in the cross-section can be calculated and the distribution profile therefore obtained. A well-documented debrisflow reference case and the Jiasikou debris flow in the high-seismic-intensity zone of the Wenchuan earthquake are selected as case studies to demonstrate the model. Analyses of both cases confirm the asymmetrical distribution of debris-flow velocity in cross-section, as originally expected. This shows that the velocity at the top surface in the middle of the channel is much larger than that at each sidewall and than the mean value calculated by former equations. The obtained velocity distribution profile is a better approximation of the observed field profiles.

AB - The asymmetrical distribution of debris-flow velocity in a cross-section has long been observed and is currently regarded as one of the most essential issues in debrisflow research. Due to a lack of quantitative models for the velocity distributions of debris flows, most studies consider only the mean velocity. However, to optimize countermeasure structures, to estimate the erosion rate, or to evaluate the constitutive equations for shear behavior, it is beneficial to know the velocity profile in a cross-section. In this paper, a generalized model of typical channel geometries (e.g., rectangular, trapezoid, or V-shape) is proposed. A description of the velocity distribution that optimizes the Manning–Strickler velocity equation for transverse distribution and Egashira’s velocity equation for vertical distribution is presented; thus, the debris-flow velocity at any point in the cross-section can be calculated and the distribution profile therefore obtained. A well-documented debrisflow reference case and the Jiasikou debris flow in the high-seismic-intensity zone of the Wenchuan earthquake are selected as case studies to demonstrate the model. Analyses of both cases confirm the asymmetrical distribution of debris-flow velocity in cross-section, as originally expected. This shows that the velocity at the top surface in the middle of the channel is much larger than that at each sidewall and than the mean value calculated by former equations. The obtained velocity distribution profile is a better approximation of the observed field profiles.

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U2 - 10.1007/s11069-014-1276-3

DO - 10.1007/s11069-014-1276-3

M3 - Article

AN - SCOPUS:84918591913

VL - 74

SP - 2053

EP - 2070

JO - Natural Hazards

JF - Natural Hazards

SN - 0921-030X

IS - 3

ER -