• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.258-258
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• 2020

홍수기시 저수지 방류량으로 인한 피해를 저감하기 위한 방법으로는 구조적인 방법과 비구조적인 방법이 있으며, 구조적인 방법으로는 저수지 제체를 증고하는 등의 방법이 있고, 비구조적인 방법으로는 홍수 관리 수리시설물의 홍수기시 효율적인 운영 등이 있다. 그동안 둑높이기 저수지를 평가하는 다양한 연구에서는 제체의 증고를 통한 홍수조절능력 평가가 주를 이뤄왔으나 홍수기시 수공구조물의 운영방법별 홍수조절효과를 다각적으로 비교 연구한 연구는 부족한 실정이다. 따라서 본 연구에서는 황룡강 유역의 장성저수지를 대상으로 빈도별 홍수량을 산정하고, 둑높이기 전후의 수공구조물 운영 방법별 홍수조절능력을 평가하였으며, 효율적인 홍수조절방법을 검토하였다. 본 연구에서는 대상지구인 장성저수지의 지배관측소인 광주관측소의 과거 기상자료를 수집하였으며 HEC-HMS (Hydrologic Modeling System)을 이용하여 50년, 100년, 200년 빈도 및 PMF 유입시 설계홍수량을 산정하였다. 각 설계홍수량의 유입 시 저수지 운영 모의에는 HEC-5 (Hydrologic Engineering Center-5) 모형을 이용하였으며, 저수지 운영기법으로 Auto ROM 과 Rigid ROM 방식을 적용하였다. 또한 둑 높이기 전후 홍수조절능력 평가는 지체시간, 시간별 홍수위, 첨두홍수량, 홍수조절률 등 다양한 평가 지표를 고려하여 수행하였다. 본 연구에서 모의한 저수지 운영기법별 둑높이기 전 후의 홍수조절효과 평가를 통해 저수지의 최적 운영방안을 도출하고 둑높이기 저수지의 하류하천에 대한 치수계획의 수립 및 보완에 활용될 수 있을 것으로 기대된다.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.765-774
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• 2023

Due to climatechange, precipitation variability has increased, leading to more frequentoccurrences of droughts and floods. To establish measures for managing waterresources in response to the increasing uncertainties of climate conditions, itis necessary to understand the variability of natural river discharge and theimpact of reservoir operation modeling considering dam inflow and artificialwater supply. In this study, an integrated rainfall-runoff and reservoiroperation modeling was applied to analyze the water supply reliability andflood risk for a multipurpose dam catchment under climate change conditions. Therainfall-runoff model employed was the modèle du Génie Rural à 4 paramètresJournalier (GR4J) model, and the reservoir operation model used was an R-basedmodel with the structure of HEC-Ressim. Applying the climate change scenariosuntil 2100 to the established integrated model, the changes in water supplyreliability and flood risk of the Happcheon Dam were quantitatively analyzed.The results of the water supply reliability analysis showed that under SSP2-4.5conditions, the water supply reliability was higher than that under SSP5-8.5conditions. Particularly, in the far-future period, the range of flood risk widened,and both SSP2-4.5 and SSP5-8.5 scenarios showed the highest median flood riskvalues. While precipitation and runoff were expected to increase by less than10%, dam-released flood discharge was projected to surge by over 120% comparedto the baseline

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.609-621
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• 2003

The purpose of this study is to evaluate the hydrological impact due to temporal land cover change by gradual urbanization of upstream watershed of Pyeongtaek gauging station of Anseong -cheon. WMS HEC-1 was adopted, and DEM with 200$\times$200m resolution and hydrologic soil group from 1:50,000 soil map were prepared. Land covers of 1986, 1990, 1994 and 1999 Landsat TM images were classified by maximum likelihood method. The watershed showed a trend that forest ＆ paddy areas decreased and urban/residential area gradually increased for the period of 14 years. The model was calibrated at 2 locations (Pyeongtaek and Gongdo) by comparing observed with simulated discharge results for 5 summer storm events from 1998 to 2001. The watershed average CN values varied from 61.7 to 62.3 for the 4 selected years. To identify the impact of streamflow by temporal area change of a target land use, a simple evaluation method that the CN values of areas except the target land use are unified as one representative CN value was suggested. By applying the method, watershed average CN value was affected in the order of paddy, forest and urban/residential, respectively.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.3
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• pp.17-27
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• 2008

In this study, three different unit hydrograph methods (Snyder, SCS, Clark) in the HEC-HMS were compared to find better fit with the observed data in the small agricultural watershed. Baran watershed, having $3.85km^2$ in size, was selected as a study watershed. The watershed input data for HEC-HMS were retrieved using HEC-GeoHMS which was developed to assist making GIS input data for HEC-HMS. Rainfall and water flow data were monitored since 1996 for the study watershed. Fifty five storms from 1996 to 2003 were selected for model calibration and verification. Three unit hydrograph methods were compared with the observed data in terms of simulated peak runoff, peak time and total direct runoff for the selected storms. The results showed that the coefficient of determination ($R^2$) for the observed peak runoff was $0.8666{\sim}0.8736$ and root mean square error, RMSE, was $5.25{\sim}6.37\;m^3/s$ for calibration stages. In the model verification, $R^2$ for the observed peak runoff was $0.8588{\sim}0.8638$ and RMSE was $9.57{\sim}11.80\;m^3/s$, which were slightly less accurate than the calibrated data. The simulated flood hydrographs were well agreed with the observed data. SCS unit hydrograph method showed best fit, but there was no significant difference among the three unit hydrograph methods.

• Journal of the Korean GEO-environmental Society
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• v.14 no.2
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• pp.19-29
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• 2013

The objective of this study is to develop a new GIS Model for calculating the hydrological geographic parameters efficiently using ArcGIS ModelBuilder. To evaluate the applicability of the new GIS Model, hydrological geographic parameters calculated by WMS and HEC-GeoHMS were compared with 5 geographic parameters from the new GIS Model. 18 reservoirs in Chungdo-gun were selected for this study. Hydrological geographic parameters used in this study are watershed area, stream length, watershed slope, stream slope and curve number. As the results of this study, the average relative error of 5 geographic parameters from all watersheds is shown more than 10.00%. In the results by the new GIS Model, hydrological geographic parameters are better efficiently and accurately to evaluate than those existing models.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.153-153
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• 2011

강변저류지 설계를 위해 주로 사용되고 있는 방법은 1차원 부정류 수치모형인 HEC-RAS의 Storage 기법이다. HEC - RAS의 Storage 기법을 이용할 경우 설계자는 유입부 설계제원과 저류용량 외에 두 개의 매개변수를 결정해 주어야 한다. 하나는 하천의 조도계수이며, 다른 하나는 횡월류 위어의 유량계수이다. 그 중 횡월류 위어 유량계수는 강변저류지 홍수조절효과에 직접적으로 영향을 주는 저류량과 관련되어 있다. 따라서 저류량을 결정하기 위한 유량계수는 기존 연구자들에 의해 다양한 산정식들이 제시되어 있다. 하지만 횡월류 유량계수가 동일한 흐름 조건에서도 산정식별로 차이를 보이고 있어서, 설계자가 어떤 유량계수를 선택하느냐가 매우 중요하다. 따라서 본 연구에서는 홍수시 발생 가능한 유량계수의 범위를 결정한 후 설계 인자별로 유량계수의 변화에 따른 강변저류지 홍수조절효과를 분석하였다. 분석 결과 유량계수에 따라 크게는 최대홍수량 대비 약 5 ~ 6% 정도의 차이를 보였다. 이는 가장 작게 산정된 홍수조절효과의 범위가 약 15 ~ 20% 정도인 것과 비교하면 큰 차이를 보이는 것으로 확인하였다. 따라서 강변저류지 홍수조절효과 산정시 발생 가능한 다양한 유량계수를 적용하여 보수적으로 설계하는 것이 바람직할 것으로 판단된다.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.3 s.18
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• pp.47-55
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• 2005

In order to design and manage the urban streams, the change of hydraulic characteristics by vegetation must be analyzed clearly. Planting criteria of vegetation in a urban stream were investigated and the design method of vegetation permission map was analyzed in this study. In addition, variations of water level due to vegetation are calculated by quasi two dimensional numerical model, HEC-RAS model and FESWMS model. Joongrang stream(Gunja bridge${\sim}$Jangan bridge reach) was selected as the case study stream. According to the criteria of vegetation, it is decided that vegetation density was $0.5{\sim}1.0$ tree/ha for selected tall tree in right floodplain and shrubs can be planted in the right and left floodplain area except the important hydraulic structures site. The selected shrubs planting simulations with three models show that water level in selected floodplain area increase approximately 12cm for the 100 year return period flood. The applicability of vegetation permission map in Korean urban stream was analyzed in this paper.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.234-234
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• 2018

댐 건설을 하게 되면 저수지 형성으로 인한 통수단면 증가가 발생하고 이에 따른 하천의 유속 및 난류 영향이 감소하게 된다. 이러한 영향으로 댐 상류 구간에서 발생한 유사량은 저수지에 퇴적하게 되고 유효저수량은 감소하게 된다. 저수지의 유효저수량 감소는 댐의 주요 기능인 용수공급, 수력발전 등의 기능 저하에 지대한 영향을 주게 된다. 특히 해외 수력발전 사업의 경우 하천 경사가 크고, 퇴사가 많이 발생하는 지역에 댐이 위치하고 있다. 이와 같은 문제 해결을 위한 중 장기적 퇴사거동 및 예측에 대한 연구가 필요한 상황이다. 본 연구에서는 파키스탄 Gulpur 지역에 설치 예정인 수력발전용 댐에 대한 장기간 퇴사모의를 위해 1차원 유사해석 모형인 HEC-RAS sediment module을 이용하였다. 퇴사모의에 적용한 모형의 입력 자료로는 총 52개년(1960-2011년)간 유사량 관측값과 20년간 유량측정 결과를 이용하였다. 유사해석 모의 시나리오는 유사 재질 비율변화에 따른 장기간 Deposited 모의와 댐의 Gate를 통한 유사 배제를 운영하는 Flushing 모의를 수행하였다. 유사해석 모의 결과 Deposited 시나리오의 경우는 저수지에서 퇴적된 유사는 대부분 Sand가 차지하게 된다. Sand의 포착률은 저수지가 가득 차기 이전에는 거의 100 % 포착이 되며, 저수지가 가득 차는 시기인 운영 20년 후에는 Sand를 포함한 전체 유사의 59%가 포착하게 되어 저수지가 한계에 도달한 것을 확인하였다. 또한, Flushing 시나리오의 경우는 Flushing 운영 기간의 변화에 따른 퇴사 포착 영향이 큰 것으로 분석되었으며, Gulpur 댐의 경우는 운영기간을 5일로 설정하는 것이 안정한 하상상태를 유지하는 것으로 검토되었다.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.3
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• pp.1-12
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• 2007

This study was conducted in order to analyze a flooded area by the overflow of a stream using hydrological and hydraulic models and to estimate the utility of the SAR satellite image by comparing a protected lowland inundation area with a past inundation area map. The research area selected for this study is Sapkyocheon, which was flooded in August 1999. The flood stage was analyzed to select an inundation area by applying flood events in August 1999. By importing analyzed flood stage data into TIN data of WMS, the inundation area of a protected lowland was selected and then compared with an flood hazard map of WAMIS. An inundation area is selected by the SAR satellite image in comparing the image of August 4, 1999 (inundation time) with the image of September 8, 2002 (after inundation). The method of selecting an inundation area with the hydraulic model of HEC-RAS can be used to select an inundation area of external overflow, but it has the limit of selecting an inundation area concerning the internal drainage. The method of using the SAR satellite image can complement the limit of an inundation area of an internal drainage but accuracy of inundation area depends on using SAR satellite image acquired at time of maximum depth.

• 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.