Discharge and extension of debris flow and its application to ocean environments in South Pacific Area

The purpose of this present study is to investigate and analyze the extension and the effect of debris flow generated in mountainous terrain due to climate change on the coastal and ocean downstream areas. As the target area of this study, the coast of Fiji in the South Pacific region affected by super hurricanes every year was selected. The category 5 Hurricane Winston in 2016 produced 42,700 tons of debris flow and caused massive damage to the entire Fiji. For debris flow analysis, mass conservation and momentum conservation equations were used as governing equations, and the finite difference method was applied to the numerical model. As a result of the analysis, the increase in the discharge of debris flow generated in the upstream mountainous area and the increase of the flow water depth extend along the downstream river to the Pacific coast, and a lot of soil run out. To check how far the debris flow moves along the river, the diffusion length of the debris flow was calculated, and the debris flow spreads over a considerable range during heavy rain. Corresponding author: Hojin Lee(hojin@chungbuk.ac.kr)