ABSTRACT

Kim, S.D.; Lee, H.J., and Jun, K.W., 2020. The impact and occurrence of sediment-mixture flow due to Cyclone Winston in the coast of Fiji Island, South Pacific. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1460–1466. Coconut Creek (Florida), ISSN 0749-0208.

Recently, global warming led to climate changes which contributed to more frequent occurrences of super cyclones on the global scale. Due to intense tropical depressions, heavy rainfall caused sediment transportation within sloped, mountainous terrains, bringing about large-scale damage of lives and properties. In particular, Fiji Island, located in the South Pacific, experienced a Category 5 tropical cyclone called Winston. As a result, more than 150,000 tons of debris was produced and more than 40% of the total population were gravely impacted. Disasters due to sediment-mixture flow are difficult to predict due to its inhomogeneous and irregular nature in terms of space and time. Therefore, combinations of various countermeasures are needed for proper protection against sediment-mixture flow. Proper understanding of sediment-mixture flow mechanism and behaviour provides a systematic means to tackle this issue. The study focuses on Fiji's Viti Levu Island as it experienced a cyclone disaster most recently. The characteristics of sediment-mixture flow along the seaside are analysed. The equations for mass conservation, momentum conservation, fine sediment, coarse sediment serve as the foundation. The liquid-solid mixture dynamic sets up the numerical model through the governing equation; the numerical model is performed using the finite difference method, represented by the elapse of time. The analysis of the results show that upstream displays an increase in water discharge and water depth, and erosion occurs more than deposition. The downstream, on the other hand, flow out along the seaside, running off a significant portion of sediments to other neighbouring seasides.

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