• Magazine of the Korean Society of Agricultural Engineers
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• v.20 no.3
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• pp.4739-4749
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• 1978

This studies were conducted to derive synthetic unitgraphs and triangular unitgraphs correlated with watershed characteristics which can be used to the estimation and control of flood for the rational development of Agricultural water resources. Derived Synthetic unitgraphs and Triangular unitgraphs can be applied to the ungaged watersheds were compared with average unitgraphs by observed data. Seven small watersheds were selected as studying basins Han, Geum, Nakdong, Yeongsan and Inchon river system. The results summarized for these studies are as follows: 1. Average unitgraphs by observed data and dimensionless unitgraphs for synthesis were derived for all river systems. 2. Peak discharge per unit area of the unitgraph, qp, was derived as qp=10-0.389-0.0424Lg with a high significance. 3. Formulas for the base width of unitgraph of 50 and 75 percent for peak flow for each water systems was adopted as Table 5. 4. The base length of the unitgraph, Tb, in hours in connection with time to peak, Tp, in hours was expressed as Tb =4.3Tp. 5. Peak discharge, Qp, were obtained as Table 6 by the Triangular form to all subwatersheds. 6. Relative errors in the peak discharge of the synthetic unitgraphs showed to be 7.3 percent to the peak of observed average unitgraphs except errors of peak discharge for Yeongsan river system. This indicates that Synthetic unitgraphs for the small watersheds of Han, Geum, Nakdong and Inchon river systems can be applied to the ungaged watersheds. On the other hand, It was confirmed that the accuracy of Instantaneous Unit Hydrograph with only 1.6 percent as relative errors was approaching more closely to the observed average unitgraph than that of synthetic unitgraph with relative errors. 23.9 percent for Yeongsan river system. 7. Errors in the peak discharge of the triangular unitgraph to the observed average unitgraph showed to be 0.6 percent to 7.5 percent which can be regarded as a high precision within the range of 200 to 500$\textrm{km}^2$ in area. On the contrary, application of triangular unitgraph within the range of 200$\textrm{km}^2$ in area has defined as a unsuitable method because of high relative errors, 26.4 percent to 61.6 percent.

• Journal of Environmental Impact Assessment
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• v.6 no.2
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• pp.61-80
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• 1997

This study tried to propose the guidelines for the ecological preservation zoning in Korea. So some related laws and regulations were inspected, which were Natural Environment Preservation Act, Nature Park Act, Cultural Asset Conservation Act, Forest Act and Urban Planning Act. In these acts, I could find several concepts related to the ecosystem that are described as the protection area. But there aren't detailed and practical characteristics in those concepts. So for making the practical concept of ecosystem preservation, I considered Multiple Use Module, Wildlife habitat model, and Environmental evaluation model. Thorough this step, the process and methodology was established for evaluating and analysing. The potentiality of the GIS system was inspected. So the TM5 scene of the site was acquired and processed by ER-Mapper, Idrisi, Arc/Info and Arcview. And several digitized data were input by scanning and vecterizing. The Erdas format was mostly exchangeable to any program. The site is the Byonsan Peninsula National Park. The forest stand information and topographic data were digitized, types of which are forest year, DBH, density, slope, aspect etc. And also the watershed boundary, roads and paths, natural and cultural resources were mapped and analysed. Modelling of preservation suitability found the dispersed patterns for the best suitable zone through all the site. And the development potential areas were checked on downwatershed. This patterns are thought to result from the forest location for the wildlife habitat and the low altitude and no-steep slopes for developing. And Early warning system concept was introduced by overlapping these two patterns on the both potential area. As the conclusions, I proposed that the preservation zone be assigned according to the watershed unit as the main ecosystem zone. This main area should be linked by the eco-corridor through the point type eco-system. Finally, I thought the comprehensive information system should be established for making the rational and efficient decision making in natural area.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.4
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• pp.119-128
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• 2006

The purpose of this study is to prepare input data for FIA (flood inundation analysis) and FDA (flood damage assessment) through rainfall-runoff simulation by HEC-HMS model. For Jinwie watershed ($737.7km^2$), HEC-HMS was calibrated using 6 storm events. Geospatial data processors, HEC-GeoHMS is used for HEC-HMS input data. The parameters of rainfall loss rate and unit hydrograph are optimized from the observed data. The results will be used for river routing and inundation propagation analysis for various flood scenarios.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.57-66
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• 2018

Water disasters such as flash floods and inundation caused by localized heavy rainfall in urban areas have a large impact on climate change but are also closely related to the increase in impervious areas as pointed out in domestic and international studies. It is difficult to secure natural green areas in urban areas that have already been developed. So, urban regeneration can be expected using water management optimized with technologies to secure infiltration and storage capacity such as Low-Impact Development technology. In this study, the water cycle improvement ability was confirmed by applying the LID technology within the district unit plan of the environmentally friendly village, and the economic feasibility of LID application was analyzed by estimating the costs and benefits of installing the facilities. The site was planned to conserve sufficient green and plans for securing the watershed infiltration and storage capacity were formulated with the application of additional LID technology, such as infiltration trenches, rain barrels and permeable pavements. The LID design method applicable to the site was established, and the water balance of the watershed was analyzed through simulations of the SWMM model. The water circulation improvement effect was confirmed through the water balance analysis, and the cost-benefits were determined according to the estimation method, and the economic analysis was conducted. This study confirms that the investment of LID technology is economically feasible for the hydrological improvement effect of the housing complex.

• Journal of Environmental Science International
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• v.25 no.2
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• pp.217-229
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• 2016

The government has conducted a plan of total maximum daily loads(TMDL), which divides with unit watershed, for management of stable water quality target by setting the permitted total amount of the pollutant. In this study, BOD concentration trends over the last 10 years from 2005 to 2014 were analyzed in the Geumho river. Improvement effect of water quality throughout the implementation period of TMDL was evaluated using the seasonal Mann-Kendall test and a LOWESS(locally weighted scatter plot smoother) smooth. As a study result of the seasonal Mann-Kendall test and the LOWESS smooth, BOD concentration in the Geumho river appeared to have been reduced or held at a constant. As a result of quantitatively analysis for BOD concentration with exploratory data analysis(EDA), the mean and the median of BOD concentration appeared in the order of GH8 > GH7 > GH6 > GH5 > GH4 > GH3 > GH2 > GH1. The monthly average concentration of BOD appeared in the order of Apr > Mar > Feb >May > Jun > Jul > Jan > Aug > Sep > Dec > Nov > Oct. As a result of the outlier, its value was the most frequent in February, which is estimated 1.5 times more than July, and was smallest frequent in July. The outlier in terms of water quality management is necessary in order to establish a management plan for the contaminants in watershed.

• Korean Journal of Ecology and Environment
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• v.45 no.4
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• pp.347-355
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• 2012

In this study, non-point pollution sources in the Yeongsan river basin are analyzed; then, the priority regions (areas divided on a small scale) of management are selected for efficient water management of the Seungcheon and Jooksan reservoirs, which were constructed as one of the 4 major rivers restoration projects. The priority regions are decided by using the criteria of the excessive rate of target water quality, non-point pollution load per unit area, total TP load and down flow distance. The results of this study are as follows. The upper 10% of the priority regions for non-point pollution management includes YB15, YB05, YB10, YB24, YB14 and YB11 for the Seungcheon reservoir watershed, and YC24, YC25, YC30, YC34, YC22 and YC17 for the Jooksan reservoir watershed. However, a few regions in each of the Seungcheon and Jooksan reservoirs need to be selected in higher order, and the non-point pollution removal facilities in the regions need to be installed with respect to budget, urgent matter, and so on.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.637-647
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• 2010

The Universal Soil Loss Equation (USLE)-based modeling systems have been widely used to simulate soil erosion studies. However the GIS-based USLE modeling systems have limitation in gully erosion evaluation which is one of the most important factor in soil erosion estimation. In this study, the integrated soil erosion evaluation system using with Sediment Assessment Tool for Effective Erosion Control (SATEEC) system, nLS and Unit Stream Power-based Erosion/Deposition (USPED) model was developed to simulate gully erosion. Gully head location using nLS model, USPED for gully erosion, and the SATEEC estimated sheet and rill erosion were evaluated and combined together with the integrated soil erosion evaluation system. This system was applied to the Haean-myeon watershed, annual average sediment-yield considering sheet, rill and gully erosion was simulated as 101,933 ton/year at the study watershed. if the integrated soil erosion evaluation system is calibrated and validated with the measured data, this system could be efficiently used in developing site-specific soil erosion best management system to reduce soil erosion and muddy water inflow into the receiving waterbody.

• Journal of Korea Water Resources Association
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• v.40 no.8
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• pp.585-600
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• 2007

The hydrologic cycle and BOD pollutant loads of all sub-watersheds were analyzed using HSPF (Hydrological Simulation Program-Fortran). At first, sensitivity analyses to water quantity (peak discharge and total volume) and quality (BOD peak concentrations and total loads) were conducted and some critical Parameters were selected. For more precise simulation, the study watershed was divided into four parts according to the landuse characteristics and used climate data and so calibrated and verified respectively. It was found that as the urban area ratio increases in the downstream direction, baseflow decreases (11.1 % $\rightarrow$ 5.0%) and the ratio of direct runoff volume(42.5 % $\rightarrow$ 56.9 %), BOD concentration (3.3 mg/L $\rightarrow$ 15.0 mg/L) and unit loads (55.4 kg/ha/year $\rightarrow$ 354.5 kg/ha/year) increase.

• Journal of Environmental Impact Assessment
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• v.10 no.2
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• pp.157-165
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• 2001

This paper presents the policy directions of total maximum daily loads(TMDL), which was recently adopted in Korea, for scientific management of water quality. The basic principles of water quality management are also discussed in this paper, along with the TMDL policy in United States as well as the previous policy in Korea. We discussed several unreasonable points out of the previous approaches, such as regulation of all point sources with equal standards, negligence of an assimilative capacity of the receiving water, and emphasis only on drinking water supply, etc.. For successful applications of the TMDL policy in Korea, the following directions are suggested: 1) the unit drainage basin for each TMDL application should be given, 2) the water body where the water quality standards should be maintained, needs to be guided, 3) the water quality parameters of TMDL should be given, 4) the technical guidances should be given for applications of water quality models, and 5) the seasonal TMDL would be allowed. In order to maximize the benefits of the TMDL policy, the local governments would need to implement the following strategies: 1) the increment of an assimilative capacity of the receiving water, 2) the effective controls of the non-point source pollution, 3) the advanced treatment of the point sources, 4) application of system optimization techniques along with effluent trade, and 5) utilization of watershed management systems.

• Journal of Environmental Science International
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• v.26 no.2
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• pp.133-146
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• 2017

This study aimed to develop strategies to re-establish the Park Nature Conservation Area in Bukhansan National Park, reflecting landscape ecological value by using the zonation program Marxan with Zones. Planning unit was set by watershed, and the basic data were mapped, considering topographical and ecological values. Mapped indicators were analyzed with the application framework of Marxan with Zones by indexing some indicators. The zones divided into Park Nature Conservation Area (Zone A), Park Nature Environment Area I(Zone B) which is reflected on the concept of Potential Park Nature Conservation Area and Park Nature Environment Area II(Zone C). The best solution for each of the scenarios was fixed through the sensitiveness analysis. From these, the final solution was selected considering five criteria including area ratio of conservation area and grouping. Lastly, the final solution was verified in the overlapped analysis with recent zonation. According to the results, the number of watersheds was 77, with an average area of $1,007,481m^2$. In terms of basic mapping and indexation, the slope index and number of landscape resources for topographical property were average 0.22 and 38 places, respectively. Biotope index was average 0.69 and legally protected species was 14 species, reflecting ecological values. As the social and economic indicators, trail index was average 0.04, and the number of tour and management facilities was 43 places. Through the framework of Marxan with Zones, the best solution for scenario 1 which was set by the highest conservation criteria was selected as the final solution, and the area ratio of Park Nature Conservation Area and grouping was excellent. As the result of overlapped analysis, suggested zonation of the Park Nature Conservation was better than the recent zonation in the area raito (28.3%), biotope grade I(15.4%) and the distribution points (10 places) of legally protected species with verification of proper distribution of conservation features according to the zone.