• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.127-127
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• 2012

수자원분야에서 강우-유출의 정확한 해석은 홍수분석 및 수자원 이용의 측면에서 중요한 과제이다. 또한, 강우-유출 해석에서 유역의 지형인자 및 수문 매개변수의 산정은 홍수량 산정을 위하여 매우 중요하며, 이와 관련된 연구도 많이 진행되었다. 이에 비하여 홍수량 산정 시 첨두유량 및 첨두시간에 큰 영향을 미치는 소유역 분할에 관한 연구는 최근 들어서야 많이 진행되고 있으며, 다른 강우-유출해석 연구에 비하여 상대적으로 부족한 실정이다. 본 연구에서는 소유역 분할에 따른 유출변화를 분석하기 위하여 시험유역으로 평창강, 청미천, 안동댐 및 임하댐 유역을 선정하였으며, 유출분석 방법으로 집중형 모형인 Clark 방법과 준 분포형 유출모형인 ModClark(Modified Clark) 방법을 이용하여 강우-유출을 모의하였다. 또한, 소유역 분할이 첨두유량과 첨두시간에 미치는 영향을 판단하기 위해 유출 매개변수의 보정과정을 거치지 않고 강우-유출을 모의하였다. ModClark 방법으로 모의 시 관측된 강우 자료를 전 유역에 걸쳐 분포시키기 위하여 IDW(Inverse Distance Weighted) 방법을 사용하였고, 공간적으로 분포된 강우자료와 지형자료를 이용함으로써 모의결과에 대한 정확도를 높이는 한편, 강우-유출 모형에서 소유역의 분할 개수에 따라 모의된 유출 형태의 변화 양상을 검토하고 실측수문곡선과 비교하였다. 소유역 분할에 따른 유출모의 결과 대체적으로 분할개수가 증가함에 따라 첨두유량은 증가하고 첨두시간은 감소하는 경향이 나타났으나, 첨두유량 및 첨두시간 모두 각각 일정분할 개수 이상에서는 변동 경향이 감소하는 것으로 나타났다.

• Journal of Korea Water Resources Association
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• v.41 no.5
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• pp.491-501
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• 2008

In order to describe runoff characteristics of urban drainage area, outflow from subbasins divided by considering topography and flow path, is analyzed through stormwater system. In doing so, concentration time and time-area curve change significantly according to basin shape, and runoff characteristics are changed greatly by these attributes. Therefore, in this development study of FFC2Q model by MLTM, we aim to improve the accuracy in analyzing runoff by adding a module that considers basin shape, giving it an advantage over popular urban hydrology models, such as SWMM and ILLUDAS, that can not account for geometric shape of a basin due to their assumptions of unit subbasin as having a simple rectangular form. For subbasin shapes, symmetry types (rectangular, ellipse, lozenge), divergent types (triangle, trapezoid), and convergent types (inverted triangle, inverted trapezoid) have been analyzed in application of time-area curve for surface runoff analysis. As a result, we found that runoff characteristic can be quite different depending on basin shape. For example, when Gunja basin was represented by lozenge shape, the best results for peak flow discharge and overall shape of runoff hydrograph were achieved in comparison to observed data. Additionally, in case of considering subbasin shape, the number of division of drainage basin did not affect peak flow magnitude and gave stable results close to observed data. However, in case of representing the shape of subbasins by traditional rectangular approximation, the division number had sensitive effects on the analysis results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.157-170
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• 2013

In this study, flood runoff characteristics is analyzed according to subbasin divisions by physically based rainfall-runoff model and appropriate number of subbasin divisions is suggested for midsize test basins. The Clark method, a lumped model in HEC-HMS, and the ModClark method, a semi-distributed model are used to simulate rainfall-runoff processes on Andong-reservoir basin, Imha-reservoir basin, and Pyeongchang river basin. The test basins were divided into nine subdivision cases by equal-area subdivision method such as single basin, 3, 5, 6, 7, 9, 10, 12, and 15 subbasins, and compared the simulated and observed values in terms of the peak flow and the peak time. The simulation results indicated that the peak flows tended to increase and the peak time shifted earlier as the number of subdivisions increased and this tendency weakened after the certain number of subdivisions. In this research, the specific number of subdivision was defined as the minimum number of subdivision considering both peak flow and peak time. Consequently, the minimum number of subdivisions is determined as 5 for Andong and Imha reservoir basins and 7 for Pyeongchang river basin.

• Journal of Korea Water Resources Association
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• v.44 no.9
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• pp.721-730
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• 2011

The objective of this study is to assess the availability of streamflow simulation using Radar-AWS Rain rate (RAR) data which is produced by KMA on real-time. Chuncheon dam upstream basin is selected as study area and total area is 4859.73 $km^2$. Mean Areal Precipitation (MAP) using AWS and RAR are calculated on 5 subbasin. The correlationship of hourly MAPs between AWS and RAR is weak on ungauged subbasins but that is relatively high on gauged ones. We evaluated the simulated discharge using the MAPs derived from two data types during flood season from 2006 to 2009. The simulated discharges using AWS on Chuncheon dam (gauged basin) are well fitted with measured ones. In some cases, however, discharges using AWS on Hwacheon dam and Pyeonghwa dam with some ungauged subbasins are overestimated on the other hand, ones using RAR in the same case are well fitted with measured ones. The hourly RAR data is useful for the real-time river forecast on the ungauged basin in view of the results.

• Water for future
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• v.27 no.4
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• pp.85-94
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• 1994

A Sensitivity analysis on the model parameters involved in the Clark watershed routing method is made to demonstrate the effect of each parameter on the magnitude of 50-year design flood for small urban streams. As for the rainfall parameter the time distribution pattern of design storm was selected. For short duration storms Huff, Yen & Chow and Japanese Central type distributions were selected and the Mononobe distribution of 24-hour design storm was also selected and tested for Clark method application. The effect of SCS runoff curve number for effective rainfall and the methods of subbasin division for time-area curve were also tested. The routing parameter, i.e. the storage constant(K), was found to be the dominating parameter once design storm is selected. A multiple regression formula for K correlated with the drainage area and main channel slope of the basin is proposed for the use in urban stream practice for the determination of design flood by Clark method.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1231-1244
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• 2008

The objective of this study is to present a methodology for estimating runoff curve number(CN) using SWAT model which is capable of reflecting watershed heterogeneity such as climate condition, land use, soil type. The proposed CN estimation method is based on the asymptotic CN method and particularly, it uses surface flow data simulated by SWAT. This method has advantages to estimate spatial CN values according to subbasin division and to reflect watershed characteristics because the calibration process has been made by matching the measured and simulated streamflows. Furthermore, the method is not sensitive to rainfall-runoff data since CN estimation is on a daily basis. The SWAT based CN estimation method is applied to Chungju dam watershed. The regression equation of the estimated CN that exponentially decays with the increase of rainfall is presented.

• Economic and Environmental Geology
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• v.53 no.4
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• pp.397-411
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• 2020

The Cretaceous Yucheon Group is volcano-sedimentary successions that are formed by volcanic activities of the Gyeongsang Volcanic Arc. Lack of the detailed field researches on the Yucheon Group results in poor understanding of the formation time and the tempo-spatial development of the volcanic arc. Also, this causes difficulties to reconstruct the depositional history from the Sindong and Hayang groups to the Yucheon Group. In this study, we conducted field research targeting to the interface between topmost part of the Hayang Group and the lowermost part of the Yucheon Group from Hyeonpoong to Bugok areas. We also identified depositional timing of the lowermost part of the Yucheon Group using SHRIMP U-Pb zircon age dating. This Yucheon Group is composed of tuff and lapilli tuff, conformably overlying the Jindong Formation. The results of SHRIMP U-Pb zircon age are 97 to 96 Ma, indicating cessation of deposition of the Hayang Group at 97 to 96 Ma by input of pyroclastic materials into the Jinju Subbasin during the explosive volcanic eruptions from the Gyeongsang Volcanic Arc. In comparison with field researches and results of LA-ICP-MS zircon U-Pb age dating (88-85 Ma) of the lowermost part of the Yucheon Group in Gyeongju areas, the volcanic activities that formed Yucheon Group and their influence ranges varied tempo-spatially. This is probably due to distance difference from the volcanic arc or establishment of the paleo-drainage system from the Gyeongsang Volcanic Arc to nearby lowlands.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.828-836
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• 2010

This study was conducted to evaluate soil erosion risk with a standard unit watershed in the upper Han river basin using the spatial soil erosion map according to the change of landuse. The study area is 14,577 $km^2$, which consists of 10 subbasins, 107 standard unit watersheds. Total annual soil loss and soil loss per area estimated were $895{\times}10^4\;Mg\;yr^{-1}$ and 6.1 Mg $ha^{-1}\;yr^{-1}$, respectively. A result of analysis with a subbasin as a unit showed that annual soil losses and soil loss per area in Namhan river basins was more than in Bukhan river ones. Predicted annual soil loss according to the landuse ranked as Forest & Grassland > Upland ${\gg}$ Urban & Fallow area > Paddy field > Orchard. Upland area covered 6.2% of the study area, but the contribution of total annul soil loss was 40.6% and that of Forest & Grassland was 44.2%. As a evaluation of soil erosion risk using the spatial soil erosion map, we could precisely conformed the potential hazardous region of soil erosion in each unit watersheds. The ratio of regions, graded as higher "Moderate" for annual soil loss, were respectively 8.7%, 7.9% and 7.8% in 1001, 1002 and 1003 subbasins in Namhan river basin. Most landuse of these area was upland, and these area is necessary to establish soil conservation practices to reduce soil erosion based on the field observation.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1265-1273
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• 2006

The environmental capacity and watershed pollution load reduction of Yongdam reservoir were estimated by the simulation of water quality variation process with the target water quality establishment, pollution load estimation and flow analysis. The potable raw water $I{\sim}II$, COD $1.0{\sim}3.0$ mg/L and TP $0.01{\sim}0.03$ mg/L were selected as the target water quality Yongdam reservoir water quality model was constructed with WASP5 contained 42 segments and the correlation of calibrated results were BOD 0.73, $PO_4-P$ 0.98. The environmental capacity for target quality COD 2.0 mg/L and TP 0.02 mg/L were BOD $131,880{\sim}4,694$ kg/d, TP $7,855 {\sim}167$ kg/d which were less than exists, and the related reduction ratios were BOD $51{\sim}62%$, TP $47{\sim}67%$ which were middle amount in exists. The load reduction ratios to meet the potable raw water $I{\sim}II$ were BOD $72{\sim}16%$, TP $78{\sim}36%$ in existing conditions and BOD $81{\sim}44%$, TP $84{\sim}52%$ in new conditions. BOD was the least one and TP was the second least in 4 results. The effects of the load reduction assignment to subbasin were dominant in TP but little in COD.