Jun, K.; Jun, B.-H.; Lee, H.; Kim, S., and Tak, W., 2018. The study of utilization and precision based on the comparison and analysis of drone-based coastal hazard data and its application in the ocean environment. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 811–815. Coconut Creek (Florida), ISSN 0749-0208. As more economic activities are developing along the coast, many studies are performed within the area concerning biological, social, economic factors closely linked to human activities. As coastal hazards occur in various categories, consistent monitoring would establish effective countermeasures and management of the coastal hazard region. Many surveys concerning seashore disasters exist already, like the bathymetric survey, beach profile survey, and shoreline survey. However, some of their disadvantages include high price, the use of equipme...

Typhoons are the main type of natural disaster in Korea, and accurately predicting typhoon-induced flood flows at gauged and ungauged locations remains an important challenge. Flood flows caused by six typhoons since 2002 (typhoons Rusa, Maemi, Nari, Dienmu, Kompasu and Bolaven) are modeled at the outlets of 24 Geum River catchments using the Probability Distributed Moisture model. The Monte Carlo Analysis Toolbox is applied with the Nash Sutcliffe Efficiency as the criterion for model parameter estimation. Linear regression relationships between the parameters of the Probability Distributed Moisture model and catchment characteristics are developed for the purpose of generalizing the parameter estimates to ungauged locations. These generalized parameter estimates are tested in terms of ability to predict the flood hydrographs over the 24 catchments using a leave-one-out validation approach. We then test the hypothesis that a more complex generalization approach, the Generalized Estimating Equation, which includes properties of the typhoons as well as catchment characteristics as predictors of PDM model parameters, will provide more accurate predictions. The results show that the predictions of Generalized Estimating Equation are comparable to those of the simpler, conventional regression. The simpler approach is therefore recommended for practical applications; however, further refinements of the Generalized Estimating Equation approach may be explored.

The purpose of this study is to analyze the impact force of debris flow by conducting numerical simulations according to the characteristics of the liquefied layer. Numerical simulations were performed based on the Finite Difference Method, and continuity equations and momentum equations were applied as the governing equations. The impacts of debris flow in the downstream direction were analyzed according to the variance of the slope angle, water supply, and the paved length of sediment including fine and coarse fractures. The higher the slope, the greater the acceleration of the velocity of debris flow as well as the mobility of water particles and soil, which results in fluctuation. The increase in water supply caused the amplitude of fluctuation to become considerably high, and the peak value of the impact force was obtained. When the paved length of sediment was longer, the impact of debris flow was found to be high in the initial section, and when the paved length of sediment was shorter, the fluctuation was faster. The results of this study can be used to evaluate the stability of disaster mitigation structures by measuring the impact force of debris flow such as check dams in mountainous regions and can provide valuable information for establishing disaster prevention measures in mountain regions.

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.

The purpose of this study is to investigate the occurrence of debris flows, including their locations, volumes, and flow in regions. The field surveys were conducted in regions using a drone and a numerical analysis was performed with the RAMMS model to simulate debris flow behavior. The results of this study were compared with the actual debris flows. As a result of comparing the detailed map (Case A) and the actual debris flow occurrence status after the debris flow in the Docheon-ri basin in the model verification, it was confirmed that the spread area and movement distance were simulated to be the same, confirming the applicability of the model. As a result of simulating the digital map (Case B) before the occurrence of debris flow under the same conditions and comparing it with the actual debris flow occurrence status, the flow direction and spread shape of the debris flow were simulated to be similar except for the area that occurred beyond the basin. It was confirmed that simulation was possible. It is believed that it can be used as basic data for damage prevention, such as estimating the extent of damage from debris flow disasters, selecting on-site investigation points for expected debris flow damage, and evacuating residents within the debris flow damage area when heavy rain is expected.Keywords: debris flow, heavy rain, RAMMS, survey, damage.