Kyu-Ho Kim

Suitability Analysis of Numerical Models Related to Seepage through a Levee

Numerical models for seepage analysis are useful tools to analyze problems and design protection techniques that are related to seepage through a levee. Though every model may have its own limitations and shortcomings, there were no generalized verifications or calibrations for the commercial models. It means that users can run the model and get the result without understanding nor taking any enough training. This paper Investigates applicability and suitability of some seepage numerical models by comparing analytical solutions with experiments in the user`s viewpoint. The results showed that it is more desirable to use analyses with unsaturated-unsteady condition rather than those with saturated-steady conditions, since seepage phenomenon of real levees are changed according to water level and soil property. This study also compared the calculated unsteady solutions with the calculated steady solutions for the levee at Koa of the Nakdong River The comparison revealed that as the result, the safety factor of has the same effects for seepage protection techniques when they are designed on the basis of steady-state analysis.

Effect of Climate Change on Environmental Flow Components and Physical Habitats

The quantity and timing of runoff are critical components for the water supply, water quality, and ecological interaction of river systems (Poff, et al., 1997). Five components of the flow regime (magnitude, frequency, duration, timing, and rate of change) can directly and indirectly impact an aquatic ecosystem. (Karr, 1991; Poff, et al., 1997). Due to the recent phenomenon of climate change, the timing and pattern of rainfall has changed and affected the flow regime of certain basins. Hence, in this research, the future impact of climate change on the river flow regime and aquatic ecosystem of the Mangyeong River, a medium-sized basin in Korea, has been quantified by analysis of environmental flow components and physical habitat modeling. Consequently, it is predicted that there will be crucial changes in the material conditions related to the river flow regime, and the risk of ecological environmental changes will greatly increase. KeywordsClimate Change; EFCs; CSI; Environmental Flow Components

Application of the LISFLOOD-FP model for flood stage prediction on the lower mankyung river

LISFLOOD-FP model in which channel flows are resolved separately from the floodplain flows using either a kinematic or diffusive wave approximation has been used to analyze flooding behavior on the lower Mankyung River influenced by backwater. A calibration and validation process was applied using the previous flood events to assess the model performance. Sensitivity analysis was conducted for main calibrated parameters, such as Manning roughness coefficient and downstream boundary condition. Also, we examined the effect of warm-up for the initial conditions. The results show that the computed hydrograph is in good agreement with measured data on the study reach, even though it was a hydrologic kinematic wave model. The sensitive analysis show that the difference between the computed results may be greater depending on the used calibrated parameters and that the sufficient calibration/validation process against various flood events is necessary. If the flood inundation simulation is performed using the validated model, it is expected to be able to contribute about river planning and policy decision-making for flood damage reduction.

A Study on Ecotope Diversity Transition Analysis in the Middle of the Mankyung River, South Korea

An ecotope is an environment where an ecological niche and habitat are combined. Ecotopes are the smallest habitat units that are homogeneously classifiable on maps. Since the diversity of classified ecotopes i closely related to biodiversity, analysing ecotope diversity should be useful for indirectly presuming ecological healthiness. In this study, ecotopes in the middle of the Mankyung River were classified by time period (1918~2014), and the changes of their diversity before and after the construction of dikes were analyzed. Based on this analysis, the ecological healthiness of the environments of the Mankyung River was evaluated. The results of this study show that, after the construction of dikes in 1948, riverside lands formed intensive ecological environments, but the ecotope diversity index of protected lowlands declined sharply due to the artificial development of roads, farmlands, houses, and rural villages. KeywordsEcotope; Diversity; Stream Environment; Habitat; Aerialphoto