• Journal of Korea Water Resources Association
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• v.38 no.5 s.154
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• pp.379-390
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• 2005

This study is to trace the change of stream shape using the past series of aortal photographs and topographic maps, and to compare the land use changes of inland along the stream. For the Gyeongan first & second class of local stream, aerial photographs of 1966, 1981 and 2000 were selected and ortho photographs were made with interior orientation and exterior orientation, respectively. In addition, topographic maps of 1914 - 1915 were used to compare with stream of 1966, 1981 and 2000. As apparent changes of the stream, the consolidated reaches of stream with levee construction were straightened and their stream width widened. Especially the stream width of inlet part of Paldang lake was widened almost twice because of the rise of water level by dam construction in 1974. The land use maps (1966, 1981, 2000) of riparian areas were also made, respectively and classified into 6 categories (water, forest, agricultural land, urban area, road, sandbar) by digitizing, The main changes of land use were agricultural land, urban area, road and sandbar.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.236-244
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• 2006

Water quality fluctuation of Gyeongan water area in Paldang reservoir, which measured from the downstream sampling point of Gyeongan stream (G1) to dam sampling point (P), was examined in the light of seasonal rainfall and regional difference in the year of 2002. Annual COD, T-P and T-N concentration dropped conspicuously at the point P (in front of dam) although concentration of Gl point was high. Concentration variation of COD, T-P and T-N from Gl to P point in Gyeongan area was small in August and September. And at G l point showed relatively low concentration. Chlorophyll-a concentration varies less during the autumn season (October to December) than spring season (March to June). Water temperature of Bughangang (north Han-river) area was relatively lower in August and higher in November compared with that of other areas. COD and SS concentration showed big regional difference except in November when the concentrations of which were relatively low. The high Chlorophyll-a concentration of April fell conspicuously in rainy season. Gyeongan area, where the water depth is relatively shallow, indicated steep temperature gradient in April compared with that in August or November. High 55 concentration in April at P point characterized surface layer while the opposite was recorded in August. Mixing of upper and lower layers had taken place causing dilution of COD, T-N and T-P concentration in August. This condition was maintained throughout November. Therefore, spring-summer seasons needed more attention for water management countermeasure than summer-autumn seasons.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.537-548
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• 2013

In this study, the hydraulic channel routing model was constructed to analysis the effect of flood control with the operation of Chungju Dam for 2006 flood. Study area was divided with up- and downstream of Chungju Dam in the upper Han River of Paldang Dam. The model was calibrated and verified for the flood event of 1995-2008. The effects of flood control of Chungju Dam were compared with the simulation results without the dam, and the rising effects of stage in the main observation stations were analyzed by the variation of released dam discharge. Consequently, the operation of Chungju Dam for 2006 flood was performed properly, but the effects of flood control of Chungju Dam were so focused in downstream of the dam that institutional complement was demanded to reduce the flood damage in the upper region of the dam. The limit of decision rule of downstream stage in the backwater region of dam was analyzed to solve the problem, and the decision rule of downstream stage was proposed to consider the discontinuity between the backwater region of dam and the design flood of upper stream. The proposed rule will be used to design the reduction of flood damage in upper stream of dam and to apply the analysis of region for flood damage.

• Journal of Korea Water Resources Association
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• v.35 no.2
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• pp.161-171
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• 2002

It has been known that the accurate estimates of 2-dimensional water quality model parameters are difficult for non-experts due to the complexity of theoretical background and input requirement and complicated inter-relationship between model Parameters. The main goal of this study is to Provide expert system for the optimal estimation of water quality model parameters, which is based on the development of chaining mechanism according to the sensitivity analysis of model parameter interactions and GUI interface system on ArcView Avenue. The selected study area is the 35.3- km main Han river starting from Paldang Dam site to the Point of Indo bridge and the tributary inflows including pollutant data are used for the system application and validation. The estimated main model parameters are 0.367 for transverse dispersion coefficient, 0.074 for and 0.162 for. It also shows that the simulated water quality constituents such as DO and BOD based on the estimated model parameters are well agreed with the observed ones. It can be concluded that the developed GIS-based expert system for water quality model parameter estimation and graphical representation of water quality analysis is useful for the scientific water quality management.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.128-128
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• 2011

본 연구에서는 자동유량측정시설에 의하여 실시간으로 생산되는 자동유량측정 자료의 정상성 여부를 판단하는데 중요한 적정 측정 신뢰구간을 실시간으로 예측할 수 있는 기술을 개발하였다. 전세계적으로, 현대적인 유량측정이 시작된 이래 연속유량 산정을 위한 방법은 수위-유량관계곡선을 이용하는 방법 외에 실무적으로 활용 가능한 방법은 거의 전무한 실정이다. 수위-유량관계곡선을 이용하는 방법은 연속수위를 계측하여 이에 해당하는 연속유량을 산정하는 방법으로 수위와 유량간에 일정한 관계를 가지는 정상적인 흐름을 보이는 자연하천의 경우에 정확도가 매우 높다. 그러나 감조나 구조물 등에 의해 유량이 조절되는 경우에 유량산정의 정확도는 현저히 떨어지게 된다. 따라서 수위에서 유량을 환산하는 방법이 아닌 유량을 직접 연속으로 측정하는 방법이 꾸준히 연구되어 왔고, 이 중 가장 대표적인 방법이 자동유량측정 방법이다. 그러나 자동유량측정 방법은 유량을 연속으로 측정할 수 있다는 장점에 반해 측정된 유량의 정확도를 높이기가 매우 어렵다는 단점도 가지고 있다. 계측 자체의 기술적 한계는 주로 계측기기적인 문제로 이는 전자기, 통신 기술 등 첨단 기술의 발전과 함께 다양한 현장 시험을 통해 폭넓은 개선이 이루어지고 있다. 그러나 아직 기술적 완성도가 완전하지 못한 현실에서, 현재 설치되어 있는 자동유량측정 유량자료의 신뢰도를 높이기 위해서는 각각의 계측 시점에서 자료가 정상적으로 산정되고 있는지에 대한 검정이 필요하고, 이는 자동유량측정 자료의 정확도 확보에 매우 중요한 관건으로 작용할 수밖에 없다. 이러한 배경에서 본 연구에서는 조석성분과 유출성분을 분리하여 예측하는 방법을 새롭게 개발 적용하였다. 자료는 자료의 시간해상도 증감에 따른 실제 예측의 정확도 증감을 고려하여 가장 적절하다고 판단되는 시자료를 사용하였으며, 자료간 상관을 분석하여 주 입력 자료로 팔당댐 방류량, 한강대교 지점 수위, 전류 수위를 이용하였다. 모형의 예측 능력을 극대화하기 위하여 조석 영향을 받는 자료의 경우는 웨이블릿 변환(wavelet transform)을 이용하여 순수 유출성분과 조위성분을 분리하여 별도로 적용하였다. 그리고 예측을 위한 모형은 실시간 자료기반 모형으로 그 안정성이 인정된 서포트벡터머신(support vector machine)을 이용하였다. 이러한 과정을 통해 한강대교 지점의 순수 유출성분과 조위성분의 유량을 각각 예측한 후 두 결과를 합성하여 최종 한강 대교 지점의 유량을 산정하였다. 조석성분을 분리하여 한강대교 지점의 유량을 예측한 결과 대부분의 예측치가 95% 예측구간에 포함되었다. 그리고 조석성분을 분리하지 않은 모형과 조석성분을 분리한 모형의 예측 능력을 비교한 결과, 조석성분을 분리한 모형이 예측이 정확도가 높았다. RMSE의 경우 분리하지 않은 모형대비 23%의 예측오차가 감소하였고, NSC의 경우 0.92에서 0.95로 예측의 정확도가 증가하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.461-461
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• 2017

기후변화 적응 유역 물순환 개선 기술은 기후변화가 진행 중에 있거나 예상되는 지역에 대하여 강우-유출수를 지연, 저류, 침투시켜 지속가능한 물순환체계를 유지 회복하도록 하는 기술이라 할 수 있다. 본 연구에서는 기후변화에 따른 국내 유역의 특성 및 기후를 반영하기 수월한 물순환 개선 및 평가시스템을 국내 기술로 개발하였다. 개발된 유역 물순환 개선 및 평가시스템은 기존 국가연구개발사업을 통해 개발되고 사업화에 성공한 바 있는 유역 물순환 평가 모형인 CAT(Catchment hydrologic cycle Assessment Tool)을 수정 및 개선하여 기후변화에 따른 영향을 평가하고 적응 대책을 수립하기 위한 실무적인 소프트웨어이다. 침투트렌치, 식생침투트렌치, 습지, 저류지, 빗물탱크 등의 물순환개선시설에 대한 효과를 평가할 수 있도록 개별시설의 제원에 따른 물순환개선 효과를 정량적으로 평가할 수 있다. 본 연구의 대상유역으로는 팔당댐 상류의 경안천 유역을 선정하였다. 경안천 유역의 기후변화에 따른 물순환 개선 기술 적용을 위해서 기후변화 시나리오 자료는 기상청 수원 측후소의 1976~2099년 FGOALS-s2, HadGEM-ES, INM-CM4 RCP8.5 시나리오를 적용하였으며 분석기간은 2020s(2010~2039), 2050s(2040~2069), 2080s(2070~2099)로 구분하였다. Baseline은 수원 측후소 과거 30년 1971~2000년 자료를 이용하였고 각 시나리오별 수문성분 및 구조적 물순환 개선기술 적용에 따른 수문성분을 비교 분석하였다. 물순환 개선기술 시나리오 중 침투시설 시나리오는 도시 면적의 20%, 설계침투량은 일본 우수저류침투기술협회 기준인 단위면적($1m^2$)당 10mm 적용하였고, 빗물저장시설 시나리오의 저장시설의 용량은 수도법시행규칙(2011)의 빗물 이용시설기준(도시면적 ${\times}0.05$)을 적용하였다. 시나리오별 강우량은 HadGEM-ES가 증가폭이 크게 나타났고 INM-CM4는 2080s에서 감소 경향을 보였다. 증발산량은 거의 모든 시나리오에서 대부분 감소하였고, 개선기술 적용에 따라 크게 증가하거나 감소폭이 줄어들었다. 직접유출량 및 중간유출량은 기후변화 시나리오별 강우증가분에 따른 미세한 증가 양상을 보였고, 개선기술 적용에 따라 약간 증가하는 양상을 보였다. 지하수유출량의 경우 침투시설 적용으로 함양량이 크게 증가함에 따라 증가폭이 매우 크게 나타났다.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1207-1216
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• 2018

Discharge or water level predictions at tidally affected river reaches are currently still a great challenge in hydrological practices. This research aims to predict water level of the tide dominated site, Jamsu bridge in the Han River downstream. Physics-based hydrodynamic approaches are sometimes not applicable for water level prediction in such a tidal river due to uncertainty sources like rainfall forecasting data. In this study, TensorFlow deep learning framework was used to build a deep neural network based LSTM model and its applications. The LSTM model was trained based on 3 data sets having 10-min temporal resolution: Paldang dam release, Jamsu bridge water level, predicted tidal level for 6 years (2011~2016) and then predict the water level time series given the six lead times: 1, 3, 6, 9, 12, 24 hours. The optimal hyper-parameters of LSTM model were set up as follows: 6 hidden layers number, 0.01 learning rate, 3000 iterations. In addition, we changed the key parameter of LSTM model, sequence length, ranging from 1 to 6 hours to test its affect to prediction results. The LSTM model with the 1 hr sequence length led to the best performing prediction results for the all cases. In particular, it resulted in very accurate prediction: RMSE (0.065 cm) and NSE (0.99) for the 1 hr lead time prediction case. However, as the lead time became longer, the RMSE increased from 0.08 m (1 hr lead time) to 0.28 m (24 hrs lead time) and the NSE decreased from 0.99 (1 hr lead time) to 0.74 (24 hrs lead time), respectively.

• Journal of Korea Water Resources Association
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• v.54 no.spc1
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• pp.1195-1204
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• 2021

Recently, local torrential rain have become more frequent and severe due to abnormal climate conditions, causing a surge in human and properties damage including infrastructures along the river. In this study, water surface elevation prediction algorithm was developed using the LSTM (Long Short-term Memory) technique specialized for time series data among Machine Learning to estimate and prevent flooding of the facilities. The study area is Jamsu Bridge, the study period is 6 years (2015~2020) of June, July and August and the water surface elevation of the Jamsu Bridge after 3 hours was predicted. Input data set is composed of the water surface elevation of Jamsu Bridge (EL.m), the amount of discharge from Paldang Dam (m³/s), the tide level of Ganghwa Bridge (cm) and the number of tweets in Seoul. Complementary data were constructed by using not only structured data mainly used in precedent research but also unstructured data constructed through wordcloud, and the role of unstructured data was presented through comparison and analysis of whether or not unstructured data was used. When predicting the water surface elevation of the Jamsu Bridge, the accuracy of prediction was improved and realized that complementary data could be conservative alerts to reduce casualties. In this study, it was concluded that the use of complementary data was relatively effective in providing the user's safety and convenience of riverside infrastructure. In the future, more accurate water surface elevation prediction would be expected through the addition of types of unstructured data or detailed pre-processing of input data.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.61-73
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• 2014

This study reviewed an application of water quality estimation using an Airborne Hyperspectral Imagery (A-HSI) and tested a part of Han River water quality (especially suspended solid) estimation with available in-situ data. The estimation of water quality was processed two methods. One is using observation data as downwelling radiance to water surface and as scattering and reflectance into water body. Other is linear regression analysis with water quality in-situ measurement and upwelling data as at-sensor radiance (or reflectance). Both methods drive meaningful results of RS estimation. However it has more effects on the auxiliary dataset as water quality in-situ measurement and water body scattering measurement. The test processed a part of Han River located Paldang-dam downstream. We applied linear regression analysis with AISA eagle hyperspectral sensor data and water quality measurement in-situ data. The result of linear regression for a meaningful band combination shows $-24.847+0.013L_{560}$ as 560 nm in radiance (L) with 0.985 R-square. To comparison with Multispectral Imagery (MSI) case, we make simulated Landsat TM by spectral resampling. The regression using MSI shows -55.932 + 33.881 (TM1/TM3) as radiance with 0.968 R-square. Suspended Solid (SS) concentration was about 3.75 mg/l at in-situ data and estimated SS concentration by A-HIS was about 3.65 mg/l, and about 5.85mg/l with MSI with same location. It shows overestimation trends case of estimating using MSI. In order to upgrade value for practical use and to estimate more precisely, it needs that minimizing sun glint effect into whole image, constructing elaborate flight plan considering solar altitude angle, and making good pre-processing and calibration system. We found some limitations and restrictions such as precise atmospheric correction, sample count of water quality measurement, retrieve spectral bands into A-HSI, adequate linear regression model selection, and quantitative calibration/validation method through the literature review and test adopted general methods.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.923-931
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• 2005

A study was carried out to identify the major causes of sediments pollution in the Paldang Lake in the vicinity of Gyeongan river. Samples from 40 sites were collected and analyzed to characterize the regional distributions of grain size, organic matter contents, and concentrations of T-N, T-P and heavy metals. contaminations. The mean grain size(Mz) ranged from sand type(Mz, $1{\sim}3\;{\phi}$) where Bukhan River and Namhan River converges at a high flow rate to silt type(Mz, $5{\sim}10\;{\phi}$) at the downstream of Gyeongancheon and Paldang lake, reflecting the water circulation in the area. Except sampling point St. 36 near the wetland, the determination coefficient($r^2$) of Mz and organic matter(LOI) was 0.88, showing that more organic matters are concentrated inside finer sediments. The concentrations of T-N and T-P in sediments were higher in the area at which Mz and organic matters are also higher. High concentrations of T-P analyzed in the sediments, ranging from $216{\sim}1,623\;{\mu}g/g$ (Avg. $769\;{\mu}g/g$) could be considered as a critical level. Adsorbed-P and NAI-P, which are easily released to the surrounding environments when physico-chemical characteristics of sediments are changed, was found to be around 20%, which was showed by the result of fractionated-P. Moreover, Principle Component Analysis(PCA), showed that high concentrations of T-N, T-P, organophilic metals (Cd, Cu, Pb, Zn) are distributed in the areas where high organic matter contents and fine grain-sized sediments are found. However, results of $I'_{geo}$ (Geoaccumulation Index) that considers the grain size of sediments showed that heavy metal concentrations in the lake was low enough to be considered as Class 1 indicating the relative degree of pollution was less than zero.