• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.34-44
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• 2016

This study is an experimental study about a facility for preventing the accumulation of floating debris at a bridge by flooding at a small river. Generally, structures installed at a small river are damaged frequently by floating debris during typhoons or localized rainfall events. On the other hand, there is no method available for preventing such damage. The facilities used in other countries to prevent such damage by the accumulation of floating debris include debris fins, deflectors, and sweeper. Among these facilities, the present study was conducted with a sweeper to investigate the damage-reducing capability through a real-scale accumulation experiment. A sweeper was installed in front of a bridge to bypass floating debris by self-rotation so that the floating debris may not be accumulate at the bridge. A small bridge model was prepared in a real-scale for the real-scale experiment. The accumulation reducing capability was compared through an accumulation experiment before and after the sweeper installation depending on the length of the debris and flow conditions. The result showed that the accumulation rate increased with increasing length of the debris or decreasing flow rate. The installation of a sweeper decreased the debris accumulation rate by a minimum of 55% to a maximum of 88% compared to the case without an installed sweeper. The result of the present study showed that the installation of a sweeper at a small river having a high potential of generating floating debris may help secure the stability of a bridge in the case of floating debris accumulation.

• Proceedings of the Korea Water Resources Association Conference
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• 2002.05b
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• pp.1179-1186
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• 2002

Macro scale distributed hydrological models simulate river discharge with better accuracy but it depends upon the grid resolution of input data. Effects of different input resolutions are studied here. Three different grid resolution input data obtained from HUBEX-IOP EEWB data and GAME Re-analysis data are used to simulate river discharge and compared against the observed one. CAME Re-analysis 1.25-degree resolution data are found quite satisfactory in larger basins, while HUBEX-IOP EEWB 10-minute resolution data are better for small catchments. GAME Re-analysis 2.5-degree resolution data did not give good result. Simulated results by using spatially interpolated data are rather worse than using original data. The Huaihe River basin $(132350\textrm{km}^2)$ is taken as the case of study.

• Journal of Korea Water Resources Association
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• v.40 no.12
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• pp.995-1005
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• 2007

This study presents a framework for optimum scale determination for small hydropower development in a river basin. The framework includes the construction of hydrology and topography data, the simulation of hydropower operation, the economic analysis, and the determination of optimum scale of the small hydropower. The optimum scale of design flow and facility are determined by Net Present Value among economic analysis indices. The investment cost is estimated by the cost function derived from the construction cost of existing small hydropower plants. The benefit from power generation is estimated by the price announced by government. The presented framework is applied to the two potential sites in Cho River basin for the dam and run-of-river type of plants. Finally, the sensitivity analysis for a design flow and scale of the plant is performed for the each site. The usage of the framework presented in the study is highly expected for the estimation of potential hydropower resources or the decision support tool for a proprietor by estimating the optimum scale and economical feasibility in advance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.600-608
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• 2017

The presence of piping in a levee body allows water seepage to occur by producing a large cavity or water tunnel within it, ultimately resulting in the failure of the river levee and differential settlement. In order to properly cope with river levee failure due to piping and establish a proper remediation method for this problem, it is necessary to analyze the failure mechanism of the river levee due to piping. Therefore, this study analyzed the shape and mechanism of river levee failure due to piping through small-scale and large-scale models and evaluated the seepage pressure distribution characteristics in the hydraulic well, which has been suggested as a remediation method for piping. According to the results of this study, as the safety factor for the piping in the river levee decreased, the river levee failure shape was more clearly shown through the small-scale model test. In the large-scale model test, the type of local damage to the levee due to the piping was identified and the evaluation showed that the hydraulic well had the largest effect on the inhibition of piping below the center of the well. A follow-up study is needed to confirm the reliability of the results. However, it is thought that this study can be utilized as the baseline data for research into the piping-induced river levee failure mechanism and for the preparation of a remediation method.

• Journal of Korea Water Resources Association
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• v.41 no.6
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• pp.643-651
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• 2008

This study was conducted to promote reliability of the simulated result for the long-term streamflow in Daecheong watershed. This system was constructed by the SSARR model that considered the effect of small scale irrigation facilities. We investigated the present condition of small scale irrigation facilities and analyzed the relation between irrigation facilities and river discharge. According to the analysis result about the effect of irrigation facilities, the error occurrence frequency was increased at the sub-basin that has many reservoirs and during the second quarter except for the 2003 year. Therefore, we created the relative equation between small irrigation facilities and river water and estimated the simulated streamflow for the main stations. Consequently, error of the runoff simulated with considering small scale irrigation facilities was decreased than that without considering small scale irrigation facilities at all.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.151-154
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• 2003

With estmating drinking water demands of Ulsan city, the amount would be increased from 523,000ton/day in 2006 to 635,000 ton/day in 2016. Also, the dependence of Nakdong River on the Ulsan city as a source of drinking water will be very high up to 54.4％ of total drinking water demands. Small-scale drinking water dam is no economical because of excessive construction cost and long construction period. However, development of riverbed and ground water of existing rivers is more economical than that of small-scale drinking water dam. In this study, to utilized Dongchun River as a drinking water resource, Modflow model was used to predict the amount of riverbed and ground water of Dongchun River basin. As a result, available amount of riverbed water was assumed in 6,000 ton/day by worst case (when perfect dry stream) and in case of ground water, it was assumed in 17,800 ton/day.

• Journal of Wetlands Research
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• v.18 no.3
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• pp.267-274
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• 2016

Sewerage supply in rural community is the important for water quality protection of water system such as river, lake and wetland. And characteristic of small scale wastewater system that have wide range of inflow and concentration in sewage should be considered for stable operation of small scale wastewater treatment plant. In this research, characteristics of flow ratio (flow / designed flow), effect on treatment efficiency of small scale wastewater treatment plant and assessment of optimal flow ratio were conducted through analysis on operation result of 18 small scale wastewater treatment plant in Bong-hwa gun. As a result, flow ratio shows the higher value during summer. However pollutants concentration in sewage was shown the higher concentration during autumn and winter. Treatment of small scale wastewater treatment plant is increased when flow ratio increased, and nutrient treatment efficiency is more sensitive to change of flow ratio than organic compound and suspended solids. According to this research result, it need to be maintained flow ratio 0.8 over value for stable treatment efficiency of small scale wastewater treatment plant.

• Journal of the Korean association of regional geographers
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• v.14 no.2
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• pp.105-113
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• 2008

The purpose of this paper is to analyze the influences of extreme flood on urban stream's habitat environment at Shincheon stream in Daegu. In case of Shincheon stream, as any extreme floods have not flowed over the artificial bank, an extreme flood have an effects on inner part of confined channel. To make riparian park along Shincheon channel, Concrete and rubber weirs are constructed. These weirs interrupted flow of running water as obstacles during extreme flood, and running water moved aside into and destructed banks of lower-flow-channel. In reach of no weir, as all small-scale topographic bedforms were eliminated, habitat environment of river ecosystem was simplified, and biodiversity of river ecosystem was decreased. As simplified riverbed become irregular bedforms through frequent small-scale-floods, river ecosystem will become vigorous.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.211-214
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• 2007

The purpose of this study was to establish the basic information for natural drainage capacity assessment in urban area. We sorted midium watershed of Han river and Nak-dong river, and selected 30 rainfall events during 1995 to 2000 according to high level of damage. The inundated area showed high watershed slope about 25% and it indicated the greatest damage around the watershed located in 200-300m of altitude. Besides, the great damage by inundation was occurred in the mountainous agriculture region, where the forest scale was high and the urbanization was being progressed gradually. However, inundated area was small in case of grassland, water tone such as riparian area, bare ground and wetland. Moreover, the inundated area was different according to river shape and characteristics of river distribution such as the density of the stream order, conservation constant of the river system, and the number of undulations in the watershed. Therefore, it showed that land use, river shape and distribution characteristics of stream influence on inundation.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.99-111
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• 2012

The purpose of this study is to identify the change of geographical (or geomorphological) location environment of the dwelling site and its cause in Daejon Basin during transition from the Bronze Age to the Proto Three Kingdoms Period. In order to achieve this goal, it was divided into (1) 'comparison of the total number of dwelling sites of a group of remains (or high-density dwelling remains)' and (2) 'comparison of the total number of dwelling sites in certain remains including locations of dwelling of two periods' and location environment was compared to each other in aspects of altitude, gradient, 'distance from the river of water available for use' and 'the difference between the highest altitude and lowest altitude of river bed of water available for use' based on change of period. The results were as follows: 1. looking at a change of individual factors, the altitude was elevated and the gradient was increased. The distance from the river of water available for use was decreased or increased in case of 'small scale river' and it was very little difference or increased in case of 'medium scale river'. The difference between the highest altitude and lowest altitude of river bed of water available for use was increased in case of 'small scale river' and it was increased or decreased in case of 'medium scale river'. If comparing the individual factors to each other, the increase and decrease of altitude, gradient and the difference between the highest altitude and lowest altitude of river bed of water available for use have the similar pattern. Especially, it was shown that the increase of gradient affected the increase of altitude and the difference between the highest altitude and lowest altitude of river bed of water available for use. In addition, it was shown that the increase and decrease of distance from the river of water available for use had the different pattern from those of altitude, gradient and 'the difference between the highest altitude and lowest altitude of river bed of water available for use'. 3. With above results, it was thought that combination of micro landform characteristics (eg. Characteristics of gradient) of low hills distributed within Daejeon Basin and rich aquatic environment surrounding the low hills affected the selection of location of dwelling sites at the time. Especially, it was shown that 'gradient and distance from the river of water available for use' were relatively more important factors for the inhabitants at the time to select the location of dwelling sites compared to 'altitude and difference between the highest altitude and lowest altitude of river bed of water available for use' upon selecting the location of dwelling.