Simulation of runout behavior of submarine debris flows over regional natural terrain considering material softening

Abstract

Evaluation of regional submarine debris flows is critical for quantitative assessment of vulnerable areas and reasonable design of geohazard mitigation measures. In this article, an efficient numerical model for kinematics of regional submarine debris flows is developed. The proposed model can simulate the runout process and morphological evolution of submarine debris flows over natural 3D terrain by solving 1D depth-averaged governing equations in a geographic information system (GIS). A strength softening equation is introduced to capture the degradation of sliding material strength during the runout process. The model is validated by a flume test, two slump tests, and a real case history of submarine debris flow (St Niklausen slide). Applications to Shenhu area, South China Sea, are presented to demonstrate the ability of the proposed model over complex natural terrain and the importance of considering material softening. Results show that the proposed model is capable of simulating the whole debris flow process and tracking the propagation of the sliding material. Simulation of submarine debris flow without material softening will underestimate the disaster consequences. In addition, the influences of the ambient fluid and the yield strength of the sliding material on its runout behavior are also discussed.

Keywords:

• Submarine debris flow
• depth-averaged model
• material softening
• impact area
• runout distance

Disclosure statement

The authors declare no conflicts of interest.

Additional information

Funding

The authors are grateful for the support from the National Program of Changjiang Young Scholars. The work in this paper was supported by the Natural Science Foundation of China (Project Nos. 52025094, 51979158, and 51639008) and the Program of Shanghai Academic Research Leader by Science and Technology Commission of Shanghai Municipality (Project No. 19XD1421900). The authors are grateful for the support from Shanghai Municipal Education Commission (Project No. 2021-01-07-00-02-E00089) and Shaanxi Key Laboratory for the Property and Treatment of Special Soil and Rock (Project No. KF2020-02).