Debris flow enlargement from entrainment: A case study for comparison of three entrainment models: Fid-Bau Portal

Debris flow enlargement from entrainment: A case study for comparison of three entrainment models

Shen, Ping / Zhang, Limin / Wong, Ho Fai / Peng, Dalei / Zhou, Shengyang / Zhang, Shuai / Chen, Chen

Abstract Material entrainment can significantly magnify debris flow volume and increase its destructive power. Despite great research efforts, entrainment is still not well understood. To meet the needs for debris flow simulation and hazard analysis, it is of practical significance to understand and evaluate existing entrainment models. In this study, we evaluate three entrainment models on an integrated single-phase continuum debris flow simulation platform. The well-documented Tsing Shan debris flow in 1990 in Hong Kong, with an initial landslide volume of 2500 m³ and a final deposit volume of 20,400 m³, is used as a benchmark to compare the three models. The characteristics and performance of each model and its model parameters are discussed. Although numerical results achieve reasonable agreement with detailed field investigations, some parameters are still determined empirically and subjectively. Despite of the imperfection, these models can be used for debris flow hazard analysis in the Hong Kong region with similar conditions. More physically-based entrainment models considering two-phase flow need to be adopted and further developed in the future.

Highlights • Material entrainment can significantly magnify debris flow volume and increase its destructive power. • Three entrainment models for debris flow simulation are evaluated and compared. • The models differ in initiation of entrainment and flow dynamics. • The performance of these entrainment models is tested on an integrated debris flow simulation platform. • The 1990 Tsing Shan debris flow, which is a well-documented high entrainment case, is used as a benchmark.