A MODEL FOR ASSESSMENT OF TREE STABILITY AND ENTRAINMENT OF WOODY DEBRIS BY FLOW SLIDES AND SHALLOW SLOPE FAILURE

Abstract

The effect of trees on the stability of soil slopes is widely studied. Tree roots can reinforce the soil slope by increasing its shear strength; moreover, trees may reduce soil moisture content through the transpiration process, which may reduce the pore-water pressure, improving the shear strength of the soil slope. Nevertheless, trees can also be felled by landslides and flow slides. Fallen trees create woody debris, which is a serious hazard precipitated by landslides, slope failures, and flow slides that increases the magnitude of the destruction caused to infrastructure and housing. The processes of tree instability and the entrainment of woody debris are important mechanisms in the study of the behaviour of woody debris in the ecosystem. Therefore, the purpose of this study is to propose a model to describe the mechanism of tree instability caused by shallow slope failures and flow slides, including the entrainment of woody debris by flow slides or debris flows. The proposed model combines a rainfall-induced shallow slope failure model, a sliding block model for flow slides runout analysis, and a tree stability model.