• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1670-1676
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• 2007

본 연구는 임진강 유역을 대상유역으로 대표지점을 선정하고 각 지점의 하상변동 예측, 저수지 퇴사량 추정, 유사 유출량 추정, 하상 상승 및 유수소통단면 축소에 따른 홍수범람규모의 증대, 저수지 용량 감소 및 상수원 취수구 매몰 등의 원인인 유사퇴적에 대한 신뢰성 있는 자료를 실측하여 제시하고자 한다. 실측된 유사량의 특성을 알아보고자 각 대표지점 별로 동일한 유량 시 유사량을 비교하여 유사량과 각 지형 인자들과의 상관관계를 분석함으로써 임진강 유역의 특성이 반영된 유사량 산정에 관한 기초이용 자료로 활용 제시하여 수자원 개발 및 관리에 보다 효율적으로 적용하는데 목적이 있다. 임진강 유역의 대표지점으로는 적성, 군남, 전곡지점을 선정하였고, 임진강 유역 대표지점의 특성으로는 적성지점(유역면적:$6,800.2km^2$, 유로연장:224.5km), 군남지점(유역면적:$4,228.5km^2$, 유로연장:204.9km), 전곡지점(유역면적:$2,152.9km^2$, 유로연장:133.0km)이다. 총유사량의 산정은 부유사와 소류사의 양을 더하여 산정하는 것이 가장 이상적이나 소류사의 채취가 어렵고 정확도가 떨어지기 때문에 채취한 부유사량에 수정 아인쉬타인 방법 등을 이용하여 구한 소류사를 더해 총유사량을 추정하는 것이 일반적이다. 따라서 본 연구에서는 임진강 유역에서는 실측한 부유사량에 수정 아인쉬타인 방법으로 추정한 소류사량을 더한 총유사량을 구하여 분석하였고, 기타 다른 유사량산정 공식들과 비교 분석하여 보았다. 부유사 농도분석 방법으로는 저농도(10,000ppm)인 시료에 적합한 여과법을 이용하여 분석하였으며, 유사 입경분포 분석방법으로는 BW관 방법을 이용하여 분석하였다. 현재까지 국내 외적으로 하천 유사량 산정과 관련된 많은 경험식들이 제시되고 있다. 하지만, 외국의 충적하천에 기초하여 개발되어진 유사량 공식들을 우리나라 하천에 무분별하게 적용하는 것은 위험스러우며, 유사량 산정 결과의 신뢰성을 높이기 위해서는 무엇보다 우리나라 하천의 지형, 수리, 수문학적 요소들이 유사 특성에 미치는 영향을 알아야 한다. 그러므로, 본 연구에서는 실측을 통한 유사량 값을 하천의 지형, 수리, 수문학적 요소들과 비교 분석하여우리나라 하천에 맞는 유사특성을 알아보고, 기타 총유사량산정 공식을 이용하여 실측한 유사량과 비교 분석하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1151-1159
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• 2014

In this study, two global simple indices are used to investigate climate variability and change in observations. Land-Ocean Contrast (LOC) is an index of area-averaged surface temperature contrast between land and ocean. Meridional Temperature Gradient (MTG) is defined as the mean meridional temperature gradient in the Northern Hemisphere from mid to high latitude and sub-tropical zonal bands. These indices have direct or indirect effects on changing in atmospheric circulations and atmospheric moisture transport from north-south or east-west into East Asia (EA). In addition, warm season hydrometeorology in EA is highly associated with water supplies for coupled human and natural systems including drinking water, irrigation, hydropower generation as well as fisheries. Therefore, in this study, we developed an empirical separation approach for summer rainfall from typhoon and monsoon. An exploratory analysis was also conducted to identify the regional patterns of summer monsoon precipitation over the Korean peninsula within the context of changes in different types of temperature gradients. The results show significant and consistent changes in summer monsoon rainfall during the summer season (June-September) in South Korea.

• Journal of Wetlands Research
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• v.16 no.4
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• pp.303-318
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• 2014

Baseflow gives a significant contribution to stream function in the regions where climatic characteristics are seasonally distinct. In this regard, variable baseflow can make it difficult to maintain a stable water supply, as well as causing disruption to the stream ecosystem. Changes in land use can affect both the direct flow and baseflow of a stream, and consequently, most other components of the hydrologic cycle. Baseflow estimation depends on the observed streamflow in gauge watersheds, but accurate predictions of streamflow through modeling can be useful in determining baseflow data for ungauged watersheds. Accordingly, the objectives of this study are to 1) improve predictions of SWAT by applying the alpha factor estimated using RECESS for calibration; 2) estimate baseflow in an ungauged watershed using the WHAT system; and 3) evaluate the effects of changes in land use on baseflow characteristics. These objectives were implemented in the Gapcheon watershed, as an ungauged watershed in South Korea. The results show that the alpha factor estimated using RECESS in SWAT calibration improves the prediction for streamflow, and, in particular, recessions in the baseflow. Also, the changes in land use in the Gapcheon watershed leads to no significant difference in annual baseflow between comparable periods, regardless of precipitation, but does lead to differences in the seasonal characteristics observed for the temporal distribution of baseflow. Therefore, the Guem River, into which the stream from the Gapcheon watershed flows, requires strategic seasonal variability predictions of baseflow due to changes in land use within the region.

• Journal of Korea Water Resources Association
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• v.51 no.4
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• pp.301-311
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• 2018

Recently, the flood inundation caused by heavy rainfall in urban area is increasing due to global warming. The variability of climate change is described in the IPCC 5th report (2014). The precipitation pattern and hydrological system is varied by climate change. Since the heavy rainfall surpassed the design capacity of the pipeline, it caused great damage in metropolitan cities such as Seoul and Busan. Inundation in urban area is primarily caused by insufficient sewer capacity and surplus overflow of river. Inundation in urban area with concentrated population is more dangerous than rural and mountains areas, because it is accompanied by human casualties as well as socio-economic damage to recover destruction of roads, brides and underground spaces. In addition, various factors such as an increase in impervious area, a short time of concentration to outlet, and a shortage of sewer capacity's lack increase flooding damage. In this study, flood inundation analysis was conducted for vulnerable areas using XP-SWMM. Also, three structural flood prevention measures such as drainage pipeline construction, detention reservoir construction, and flood pumping station construction are applied as flood damage prevention alternatives. The flood data for each alternative were extracted by dividing the basin by grid. The Spatial Compromise Programming are applied using flood assessment criteria, such as maximum inundation depth, inundation time, and construction cost. The purpose of this study is to reflect the preference of alternatives according to geographical condition even in the same watershed and to select flood defense alternative considering regional characteristics.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.101-108
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• 1985

The sea water exchange of Koje Bay in the southeastern part of the Korean Peninsula was estimated on the basis of current measurements and oceanographic observation. The exchange ratio was estimated by salinity differences and tidal prism method. The range of exchange ratio at the central part at the entrance of the bay is estimated to be around $26\%$ at spring tide and 5 to $15\%$ at neap tide. The magnitude of exchange ratio, however, can be changed due to water exchange, hydrometeorological and geomorphological conditions. The flushing time deduced by tidal prism was about 48 hours at spring tide and 81 hours at neap tide. Tidal induced eddy motion may play an important role on the seawater exchange in the bay.

• Journal of Korea Water Resources Association
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• v.46 no.11
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• pp.1129-1140
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• 2013

Precipitation is one of the important factors in the hydrological cycle. It needs to understand accurate of spatial precipitation field because it has large spatio-temporal variability. Precipitation data obtained through the Tropical Rainfall Monitoring Mission (TRMM) 3B43 product is inaccurate because it has 25 km space scale. Downscaling of TRMM 3B43 product can increase the accuracy of spatial precipitation field from 25 km to 1 km scale. The relationship between precipitation and the normalized difference vegetation index(NDVI) (1 km space scale) which is obtained from the Moderate Resolution Imaging Spectroradiometers (MODIS) sensor loaded in Terra satellite is variable at different scales. Therefore regression equations were established and these equations apply to downscaling. Two renormalization strategies, Geographical Difference Analysis (GDA) and Geographical Ratio Analysis (GRA) are implemented for correcting the differences between remote sensing-derived and rain gauge data. As for considering the GDA method results, biases, the root mean-squared error (RMSE), MAE and Index of agreement (IOA) is equal to 4.26 mm, 172.16 mm, 141.95 mm, 0.64 in 2009 and 17.21 mm, 253.43 mm, 310.56 mm, 0.62 in 2011. In this study, we can see the 1km spatial precipitation field map over Korea. It will be possible to get more accurate spatial analysis of the precipitation field through using the additional rain gauges or radar data.

• Journal of Korea Water Resources Association
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• v.39 no.2 s.163
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• pp.151-160
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• 2006

In this study, threshold runoff which is a hydrologic component of flash flood guidance(FFG) is estimated by using Manning's bankfull flow and Geomorphoclimatic Instantaneous Unit Hydrograph(GcIUH) methods on Han River watershed. Geographic Information System(GIS) and 3' Digital Elevation Model database have been used to prepare the basin parameters of a very fine drainage area($1.02\~56.41km^2$), stream length and stream slope for threshold runoff computation. Also, cross-sectional data of basin and stream channel are collected for a statistical analysis of regional regression relationships and then those are used to estimate the stream parameters. The estimated threshold runoff values are ranged from 2 mm/h to 14 mm/6hr on Han River headwater basin with the 1-hour duration values are$97\%$ up to 8mm and the 6-hour values are $98\%$ up to 14mm. The sensitivity analysis shows that threshold runoff is more variative to the stream channel cross-sectional factors such as a stream slope, top width and friction slope than the drainage area. In comparisons between the computed threshold runoffs on this study area and the three other regions in the United States, the computed results on Han River watershed are reasonable.

• Journal of Korea Water Resources Association
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• v.51 no.5
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• pp.439-449
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• 2018

Many potential sources of bias are used in several steps of the radar-rainfall estimation process because the hydrological and meteorological radars measure the rainfall amount indirectly. Previous studies on radar-rainfall uncertainties were performed to reduce the uncertainty of each step by using bias correction methods in the quantitative radar-rainfall estimation process. However, these studies do not provide comprehensive uncertainty for the entire process and the relative ratios of uncertainty between each step. Consequently, in this study, a suitable approach is proposed that can quantify the uncertainties at each step of the quantitative radar-rainfall estimation process and show the uncertainty propagation through the entire process. First, it is proposed that, in the suitable approach, the new concept can present the initial and final uncertainties, variation of the uncertainty as well as the relative ratio of uncertainty at each step. Second, the Maximum Entropy Method (MEM) and Uncertainty Delta Method (UDM) were applied to quantify the uncertainty and analyze the uncertainty propagation for the entire process. Third, for the uncertainty quantification of radar-rainfall estimation at each step, two quality control algorithms, two radar-rainfall estimation relations, and two bias correction methods as post-processing through the radar-rainfall estimation process in 18 rainfall cases in 2012. For the proposed approach, in the MEM results, the final uncertainty (from post-processing bias correction method step: ME = 3.81) was smaller than the initial uncertainty (from quality control step: ME = 4.28) and, in the UDM results, the initial uncertainty (UDM = 5.33) was greater than the final uncertainty (UDM = 4.75). However uncertainty of the radar-rainfall estimation step was greater because of the use of an unsuitable relation. Furthermore, it was also determined in this study that selecting the appropriate method for each stage would gradually reduce the uncertainty at each step. Therefore, the results indicate that this new approach can significantly quantify uncertainty in the radar-rainfall estimation process and contribute to more accurate estimates of radar rainfall.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.971-976
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• 2004

하천유지를 위한 하천내 최소유량의 충족은 사실상 환경문제에 제공되는 것으로서 기본적으로 하천변 수생식물의 생태계 서식처를 유지하거나 복원하기 위해 제공된다. 또한 하천유지유량은 하천의 고유종 동${\cdot}$식물을 보전하고, 아름다운 하천에 대한 심미적 질을 유지하며 여가활동 및 상업적 어획고를 최대로 늘릴 수 있거나 과학적 또는 문화적 관심사의 특성을 보호하는 기능을 위한 목적으로도 제공된다. 그러므로 생태학적인 하천유지유량 차원에서 무엇보다 중요한 것은 충분한 물을 확보하고 쾌적한 하천을 유지할 수 있는 맑은 물을 하천에 흐르도록 하는 것이다. 이와 더불어 하천의 생태학적인 측면에서는 서식지 보호를 고려한 계획이 뒷받침되어야 할 것이다. 기존의 개발은 하천정비, 골재채취, 수중 보와 하구 둑 등 하천시설물 건설, 그리고 댐 및 교량건설 등 인위적인 요인에 의하여 하천환경이 심각하게 변화는 경우가 많다. 특히 댐 건설로 인해 하류지역에 수리학적 변화와 하상 변동 등이 발생하고, 이로 인하여 생태계의 변화를 초래하기도 한다. 따라서 본 연구에서는 금강 최상류에 건설된 용담다목적댐에 의해 인위적으로 하천유입량이 감소하고 이로 인해 발생할 수 있는 수리학적 변화를 모의하여 댐 건설이 금강 상류에 미치는 영향을 분석하고자 한다. 이를 위해 2차원 유한요소모형을 이용하였으며, 댐 건설전 자연유출량 및 댐 건설후 하천유지유량에 의한 하천의 건조면적, 습지면적을 산정하였다. 또한 하천의 한계소류력과 하도를 형성하는 재료에 따라 바닥면 전단응력을 산정하여 그 차(差)를 활용하여 유량에 따른 유사이송현황을 모의하였다. 모의된 결과를 visual하게 표현하고자 GIS 기법을 이용하여 주요구간에 대한 유사이송현황을 도시하였다.유역의 고도차를 이용한 흐름특성 분석을 위해 수치고도자료를 이용하여 유역흐름특성을 분석할 수 있는 TOPAZ(Topographic PArameteri-Zation) 프로그램을 이용하였다. TOPAZ 프로그램을 통해 분석된 각 격자별 분포형 수문 매개변수는 적합한 관계식을 통해 분포형 유출량을 모의하는데 적용된다.다 정확한 유입량 예측이 가능할 것으로 사료된다.이 작은 오차를 발생하였으며, 전체적으로 퍼프 모형이 입자모형보다는 훨씬 적은 수의 계산을 통해서도 작은 오차를 나타낼 수 있다는 것을 알 수 있었다. 그러나 Gaussian 분포를 갖는 퍼프모형은 전단흐름에서의 긴 유선형 농도분포를 모의할 수 없었고, 이에 관한 오차는 전단계수가 증가함에 따라 비선형적으로 증가하였다. 향후, 보다 다양한 흐름영역에서 장${\cdot}$단점 분석 및 오차해석을 수행한 후에 각각의 Lagrangian 모형의 장점만을 갖는 모형결합 방법을 제시할 수 있을 것으로 판단된다.mm/$m^{2}$로 감소한 소견을 보였다. 승모판 성형술은 전 승모판엽 탈출증이 있는 두 환아에서 동시에 시행하였다. 수술 후 1년 내 시행한 심초음파에서 모든 환아에서 단지 경등도 이하의 승모판 폐쇄 부전 소견을 보였다. 수술 후 조기 사망은 없었으며, 합병증으로는 유미흉이 한 명에서 있었다. 술 후 10개월째 허혈성 확장성 심근증이 호전되지 않아 Dor 술식을 시행한 후 사망한 예를 제외한 나머지 6명은 특이 증상 없이 정상 생활 중이다 결론: 좌관상동맥 페동맥이상 기시증은 드물기는 하나, 영유아기에 심근경색 및 허혈성 심근증 또는 선천성 승모판 폐쇄 부전등을 초래하는 심각한 선천성 심질환이다. 그러나 진단 즉시 직접 좌관상동맥-대동맥 이식술로 수술

• Journal of Korea Water Resources Association
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• v.56 no.3
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• pp.173-184
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• 2023

Due to climate change, algal blooms frequently occur not only in Korea but also around the world, and the risk of toxicity of harmful algae has recently been issued. It is known that the representative harmful algae, cyanobacteria, are caused by the intersection of three factors: water temperature, residence time, and nutrients. In this study, water quality simulation was carried out using EFDC, a three-dimensional numerical model, to analyze the variations in water quality due to the decrease of residence time according to the opening of Yeongju Dam in Naeseong-Cheon. In fact, the concentration of chlorophyll-a in Yeongju Dam in the summer of 2021 was significant, exceeding the 'algae warning' for a long time based on the previous algae warning system. On the other hand, as a result of performing the simulation under the condition that the dam gate was completely opened, the concentration of chlorophyll-a was mostly reduced below the 'algae warning' level during the simulation period. It was confirmed that reducing the residence time by restoring the flow of Naeseong-Cheon is a way to immediately reduce algae in Yeongju Dam.