• Water Engineering Research
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• 제6권4호
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• pp.179-187
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• 2005

This paper introduces the Cheonggye-cheon restoration project. The restoration project aims to revive the 600-year-old city of Seoul by recovering the historical heritage, guaranteeing safety from the deteriorated covering structures, creating the environment-friendly space, and revitalizing the neglected city centers. In order to understand the current hydrological cycle of the Chenggye-cheon watershed, the annual water balance of the region was calculated using the observed data including precipitation, runoff, water supply and sewage, and the changes in the groundwater level. The $2001{\sim}2002$ data were used to calibrate the WEP, and the $2003{\sim}2004$ data were used to verify the WEP. The calibration and validation results for the flood hydrograph how a reasonable value (at Majanggyo station, the R2 for the calibration period was 0.9, and that for the validation period was 0.7). According to the annual water balance of the Cheonggye-cheon watershed for 2004, the amount of surface runoff, infiltration, and evapotranspiration was 1,097mm, 216mm and 382mm, respectively, for an annual precipitation of 1,499mm. The application results from WEP, a distributed hydrological model, provide more detailed information of the watershed, and the model will be useful for improving the hydrological cycle in urban watershed.

• 물과 미래
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• 제9권2호
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• pp.76-86
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• 1976

The 30-year design flood hydrograph for the Musim Representative Basin, one of the study basins of the International Hydrological Program, is synthesized by the method of unit hydrograph. The theory of unit hydrograph has been well known for a long time. However, the synthesis of flood hydrograph by this method for a basin with insufficient hydrologic data is not an easy task and hence, assumptions and engineering judgement must be exercized. In this paper, the problems often encountered in applying the unit hydrograph method are exposed and solved in detail based on the theory and rational judgement. The probability rainfall for Cheonju Station is transposed to the Musim Basin since it has not been analyzed due to short period of rainfall record. The duration of design rainfall was estimated based on the time of concentration for the watershed. The effective rainfall was determined from the design rainfall using the SCS method which is commonly used for a small basin. The spatial distribution of significant storms was expressed as a dimensionless rainfall mass curve and hence, it was possible to determine the hyetograph of effective design storm. To synthesize the direct runoff hydrograph the 15-min. unit hydrograph was derived by the S-Curve method from the 1-hr unit hydrograph which was obtained from the observed rainfall and runoff data, and then it was applied to the design hyetograph. The exsisting maximum groundwater depletion curve was derived by the base flow seperation. Hence, the design flood hydrograph was obtained by superimposing the groundwater depletion curve to the computed direct runoff hydrograph resulting from the design storm.

• 한국방재학회 논문집
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• 제7권4호
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• pp.107-113
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• 2007

The Kuem-River, one of the largest rivers in Korea, is the primary water source for more than 4 million people in Kongju city and surrounding area. To study the effect of stormwater runoff to CSOs, twelve monitoring sites were selected in two large cities (City of Kongju and City of Buyeo) near the Kuem-River. Monitoring was reformed by collecting grab samples, measuring flow rates during dry and wet seasons during over two rainy seasons. Generally the flow rate of wastewater in combined sewers was rapidly decreased after 23:00 P.M. and gradually increased from 06:30 A.M. in all sites during the dry season. The concentrations of pollutant increase approximately 5 to 7 fold for TSS and 1.5 to 2.5 fold for BOD during the rainy season. Monitoring and statistical analysis show that the groundwater contributes on sewage volume increase (average 25-45% more) during dry periods and the stormwater runoff contributes approximately 51-72% increase during rainy periods. Generally the concentrations of combined sewage were more polluted during the first flush period than after the first flush during a storm event.

• 한국농공학회지
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• 제38권5호
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• pp.64-73
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• 1996

When typhoon occurs, the meteorological conditions get worse and can cause a large damage from storm and flood . This damage, however, can be minimized if a precise analysis of the runoff characteristics by typhoon tracks is used in the flood contorl This paper aims at the analysis of storm occurrence and runoff characteristics by typhoon tracks in Nakdong river basin. Therefore, the data of 14 typhoons which invaded Nakdong river basin during the period from 1975 to 1991 were collected, analyzed, and studied. The major results of this study are as followings; 1) The frequency of the typhoon occurrence here in Korea was affected by the storms three times a year on the average. The highest-recorded frequency was during the months of July to September. 2) The survey of the track characteristics depending on the forms of the storm in the Nakdong river basin showed that typhoon storm advanced from the south of the basin to the north, while the frontal type storm was most likely to advanced from the west to the north. 3) Typhoon tracks are classified into three categories, 6 predictors with high correlation coefficient are finally selected, and stepwise multiple regression method are used to establish typhoon strom forecasting models. 4) The riview on the directions of progress of the storm made it clear that the storm moving downstream from upstream of the basin could develop into peak discharge for ca short time and lead to more flood damage than in any other direction.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2009년도 춘계 종합학술대회 논문집
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• pp.432-436
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• 2009

최근 개발에 따른 토지이용 변화로 유역내 강우의 도달시간이 짧아지고, 집중호우가 빈번하게 발생함에 따라 유출량이 증가하여 많은 홍수피해가 일어나고 있다. 유출량 증가는 하천 수위를 상승시켜 하천주변에 막대한 재산피해를 주고 있으므로 유역의 정확한 유출량 산정이 선행되어야 한다. 산정된 유출량을 바탕으로 홍수재해 발생시 예상되는 홍수범람지역을 추정함으로써 홍수피해를 예방하고, 최소화시키는 것이 필요하다. 실무에서 범용적으로 사용하고 있는 HEC-HMS 모형을 이용하여 남대천 유역의 빈도별 확률강우량에 대한 유출량을 산정하였다. 또한 이로부터 모의된 첨두홍수량을 하도수리분석을 위한 경계조건으로 사용하여 남대천 하류구간의 홍수위를 HEC-RAS 모형에 의해 분석하였다.

• 물과 미래
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• 제29권3호
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• pp.153-161
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• 1996

최근에 도시화 된 산본천 유역을 대상으로 한 유출 해석이다. 실측한 각종 자료를 유출해석 모형인 ILLUDAS를 이용하여 도시화에 따른 첨두유량과 총유출량의 연구를 분석하였다. 도시하천에서 첨두유량의 증가는 도시화에 따른 하정비가 가장 큰 영향이 있는 것으로 판단된다. 첨두유량은 강우 지속시간이나 재현기간에 따라 조도계수 n=0,04일 경우에 최대 10%까지, n=0.015일 경우는 7~16%이었으며, 또한 자연하도(n=0.04)에서 계획하도(n=0.015)로 변화하면 첨두유량은 51~158%까지 큰 폭의 증가를 보였다. 일반적으로 호우시 홍수첨두유량은 증가하지만 도시유역의 경우는 배수계통의 정비로 유속이 증가하면서 하천 수위는 오히려 감소하는 것으로 나타났다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.151-151
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• 2018

The present study is aimed to quantifying the uncertainty in the general circulation model (GCM) selection and its impacts on hydrology studies in the basins. For this reason, 13 GCMs was selected among the 26 GCM models of the Fifth Assessment Report (AR5) scenarios. Then, the climate data and hydrologic data with two Representative Concentration Pathways (RCPs) of the best model (INMCM4) and worst model (HadGEM2-AO) were compared to understand the uncertainty associated with GCM models. In order to project the runoff, the Precipitation-Runoff Modelling System (PRMS) was driven to simulate daily river discharge by using daily precipitation, maximum and minimum temperature as inputs of this model. For simulating the discharge, the model has been calibrated and validated for daily data. Root mean square error (RMSE) and Nash-Sutcliffe Efficiency (NSE) were applied as evaluation criteria. Then parameters of the model were applied for the periods 2011-2040, and 2070-2099 to project the future discharge the five large basins of South Korea. Then, uncertainty caused by projected temperature, precipitation and runoff changes were compared in seasonal and annual time scale for two future periods and RCPs compared to the reference period (1976-2005). The findings of this study indicated that more caution will be needed for selecting the GCMs and using the results of the climate change analysis.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2020년도 학술발표회
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• pp.118-118
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• 2020

This study investigates the change of flow characteristics over 10 Asian river basins in the past 30 years (1976-2005). The variation is estimated from The Soil and Water Assessment Tool (SWAT) model outputs based on reanalysis data which was bias-corrected for Asian monsoon reagion. The model was firstly calibrated and validated using observed data for daily streamflow. Four statistical criteria were applied to evaluate the model performance, including Coefficient of determination (R2), Nash - Sutcliffe model efficiency coeffi cient (NSE), Root mean square error-observations standard deviation ratio (RSR), and Percentage Bias (PBIAS). Then parameters of the model were applied for the historical period 1976-2005. The estimates show a temporal non-considerable increasing rate of daily streamflow in most of the basins over the past 30 years. The difference of monthly discharge becomes more significant during the months in the wet season (June to September) in all basins. The seasonal runoff shows significant difference in Summer and Autumn, when the rainfall intensity is higher. The line showing averaged runoff/rainfall ratio in all basins is sharp, presenting high variation of seasonal runoff/rainfall ratio from season to season.

• 대한토목학회논문집
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• 제36권5호
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• pp.779-789
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• 2016

강우-유출 모의 과정에서 유효강우는 토양수분을 고려하여 산정되며, 이러한 토양수분을 강우-유출 모형에 반영하기 위해서는 직접 관측된 자료를 활용하거나, 모형 내부에서 간접적으로 산정한다. 본 연구에서 사용한 강우-유출 모형은 유역의 기온에 따른 유역습윤지수(Catchment Wetness Index, CWI)를 산정하고, CWI와 강수량의 조합을 통해 산정되는 토양수분지수(Soil Moisture Index, SMI)를 직접 활용하여 유효강우 및 유출량을 계산하는 IHACRES 모형을 사용하여 연구를 수행했다. 합천댐 유역을 대상으로 CWI와 유효강우 간의 관계가 장기 유출 산정에 미치는 영향에 대해 연구한 결과, CWI와 유효강우는 비선형적인 관계를 가짐을 확인하였으며 이러한 비선형 관계는 장기 유출 모의에 있어 홍수기 보다 비홍수기에서 더 많은 영향을 미침을 확인하였다. CWI가 장기 유출에 미치는 영향을 자세히 분석하고자, 보정기간(2002~2004년)과 검정기간(2005~2007년)으로 나누어 가변 CWI와 일정 CWI 조건하에서 유황에 따른 유출모의성능을 분석하였다. 분석결과 전반적으로 가변 CWI의 결과가 일정 CWI의 결과에 비하여 우수하게 나타났다. 풍수기에서 결정계수는 평수기나 갈수기에 비하여 높은 값을 보이고 있으나 가변 CWI와 일정 CWI간에 차이는 크지 않았다. 이는 강수량이 많은 시기의 유출의 경우 기온에 따른 증발 및 토양수분에 대한 민감도가 상대적으로 작다는 것을 의미한다. 반면, 풍수기에 비해 유출량이 적은 평수기와 갈수기에서는 가변 CWI의 평가지표가 더 우수한 결과를 보이고 있어, 평갈수량을 포함한 장기유출모의시 기온을 고려한 증발과 이에따른 토양수분의 고려가 유출량 산정에 상당한 영향을 미침을 확인할 수 있다. NSE의 경우 풍수기가 평갈수기보다 다소 떨어지는 경향을 볼 수 있으나 NSE가 이상치의 영향을 크게 받는 지표이므로 유량 절대값이 큰 풍수기에서는 당연한 결과라 볼 수 있으며, 그럼에도 전체적으로는 0.9이상의 양호한 수치를 보여주고 있다. 풍수기에는 기온에 따른 CWI가 크게 영향을 미치지 못하지만, 유출량이 적은 평 갈수기에서 CWI의 활용이 장기 유출 모의 정확도를 개선할 수 있을 것이라 사료된다.

• 한국수자원학회논문집
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• 제38권12호
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• pp.1061-1072
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• 2005

본 연구에서는 영산호의 상류에 위치한 나주유역의 홍수시 유출량을 실시간으로 예측하기 위하여 Grey홍수 유출모형을 개발하였다. 나주유역의 유출량은 나주수위관측소에서 실시간으로 측정하고 있으며, 이곳은 영산호의 유입홍수량을 예측과 홍수관리를 위한 주관측소이다. 모형의 지배방정식은 Grey시스템 이론에 근거하여 구성되었으며, 모형의 매개변수는 Grey 시스템매개변수의 조합으로 구성하였다. 모형의 차수는 실측자료와 모의결과를 비교하여 다른 차수 보다 양호한 결과를 나타내는 5차로 하였다. 모형의 보정시 예측결과와 실측치간의 RMSE는 $3.1\~290.5m^{3}/sec$를 나타냈으며, $R^{2}$는 $0.909\~0.999$를 나타냈다. 모형의 검정시 예측결과와 실측치간의 RMSE는 $20.6\~147.4m^{3}/sec$를 나타냈으며, $R^{2}는\;0.940\~0.998$를 나타냈다. 매개변수가 추정된 모형을 이용하여 담수호의 유입량을 하천수위 상태에 따라 예측한 결과, 하천수위가 상승할 경우와 하강할 경우의 예측 홍수량은 예측시간이 증가할수록 커지는 경향을 나타냈다. 또한, 하천수위가 첨두에 가까운 시기의 홍수량은 예측시간에 관계없이 실측자료와 비슷한 결과를 나타냈다. 이와 같은 결과는 Grey 홍수유출모형을 홍수시 담수호 유입량을 실시간으로 정확하게 예측하는데 적용할 수 있음을 나타낸다.