• Journal of Korea Water Resources Association
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• v.50 no.4
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• pp.223-232
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• 2017

The ability to defend against floods in urban areas was weakened, because the increase in the impervious rate of urban areas due to urbanization and industrialization and the increase in the localized torrential rainfall due to abnormal climate. In order to reduce flood damage in urban areas, various runoff reduction facilities such as detention ponds and infiltration facilities were installed. However, in the case of domestic metropolitan cities, it is difficult to secure land for the installation of storm water reduction facilities and secure the budget for improving the aged pipelines. Therefore, it is necessary to design a storage system (called the detention pond in trunk sewer) that linked the existing drainage system to improve the flood control capacity of the urban area and reduce the budget. In this study, to analyze the effect of reducing runoff amounts according to the volume of the detention pond in trunk sewer, three kinds of virtual watershed (longitudinal, middle, concentration shape) were assumed and the detention pond in trunk sewer was installed at an arbitrary location in the watershed. The volume of the detention pond in trunk sewer was set to 6 cases ($1,000m^3$, $3,000m^3$, $5,000m^3$, $10,000m^3$, $20,000m^3$, $30,000m^3$), and the installation location of the detention pond in trunk sewer was varied to 20%, 40%, 60%, and 80% of the detention pond upstream area to the total watershed area (DUAR). Also, using the results of this study, a graph of the relationship and relational equation between the volume of the detention pond in trunk sewer and the installation location is presented.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.3
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• pp.299-309
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• 2006

In recent years, a large natural disasters have occurred due to worldwide abnormal weather and the amount of damage has been increased more resulting from high density population and a large-sized buildings of the urbanized area. In this study. we estimate the flooded area according to rainfall probability intensify and sea level in Woreong dong, Masan occurred flood damages by typhoon Maemi using SWMM, a dynamic rainfall-runoff simulation model in urban area, and then analyze the damage of flood expected area through connecting with GIS database. In result, we can predict accurately expected area of inundation according to the rainfall intensity and sea level rise through dividing the study area into sub-area and estimating a flooded area and height using SWMM. We provide also the shelter information available for urban planning and flood risk estimation by landuse in expected flood area. Further research for hazard management system construction linked with web or wireless communication technology expects to increase its application.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.139-145
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• 2010

Recently, close-to-nature stream improvement works have been carried out in urban streams, where eco-friendly bank revetment methods have been adopted. These bank revetment methods are vulnerable to be damaged or washed away by floods compared to the traditional methods which use concrete materials. Damage analysis methods on the urban streams by the floods of severe rain storm are presented. The analysis methods are the graph-using method and the grid method, which are derived from the survey results at Gwangju stream. Damage analysis grid which is intersected velocity grid and material strength grid is the highest correlation with the damage survey grid. The biggest damage on the bank revetments have been occurred around the crossing structures. Big damages have also been occurred in the connection of low water revetment and the terrace land, and around the structures in the terrace land of the stream.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.321-331
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• 2006

Recently, runoff characteristics of urban area are changing because of the increase of impervious area by rapidly increasing of population and industrialization, urbanization. It needs to extract the accurate topologic and hydrologic parameters of watershed in order to manage water resource efficiently. Thus, this study developed more precise input data and more improved parameter estimating procedures using GIS(Geographic Information System) and GA(Genetic Algorithm). For these purposes, XP-SWMM (EXPert-Storm Water Management Model) was used to simulate the urban runoff. The model was applied to An-Yang stream basin that is a typical Korean urban stream basin with several tributaries. The rules for parameter estimation were composed and applied based on quantity parameters that are investigated through the sensitivity analysis. GA algorithm is composed of these rules and facts. The conditions of urban flows are simulated using the rainfall-runoff data of the study area. The data of area, slope, width of each subcatchment and length, slope of each stream reach were acquired from topographic maps, and imperviousness rate, land use types, infiltration capacities of each subcatchment from land use maps, soil maps using GIS. Also we gave the management scheme of urbanization runoff using XP-SWMM. The parameters are estimated by GA from sensitivity analysis which is performed to analyze the runoff parameters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.3
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• pp.273-283
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• 2020

Because of climate change, the occurrence of localized and heavy rainfall is increasing. It is important to predict floods in urban areas that have suffered inundation in the past. For flood prediction, not only numerical analysis models but also machine learning-based models can be applied. The LSTM (Long Short-Term Memory) neural network used in this study is appropriate for sequence data, but it demands a lot of data. However, rainfall that causes flooding does not appear every year in a single urban basin, meaning it is difficult to collect enough data for deep learning. Therefore, in addition to the rainfall observed in the study area, the observed rainfall in another urban basin was applied in the predictive model. The LSTM neural network was used for predicting the total overflow, and the result of the SWMM (Storm Water Management Model) was applied as target data. The prediction of the inundation map was performed by using logistic regression; the independent variable was the total overflow and the dependent variable was the presence or absence of flooding in each grid. The dependent variable of logistic regression was collected through the simulation results of a two-dimensional flood model. The input data of the two-dimensional flood model were the overflow at each manhole calculated by the SWMM. According to the LSTM neural network parameters, the prediction results of total overflow were compared. Four predictive models were used in this study depending on the parameter of the LSTM. The average RMSE (Root Mean Square Error) for verification and testing was 1.4279 ㎥/s, 1.0079 ㎥/s for the four LSTM models. The minimum RMSE of the verification and testing was calculated as 1.1655 ㎥/s and 0.8797 ㎥/s. It was confirmed that the total overflow can be predicted similarly to the SWMM simulation results. The prediction of inundation extent was performed by linking the logistic regression with the results of the LSTM neural network, and the maximum area fitness was 97.33 % when more than 0.5 m depth was considered. The methodology presented in this study would be helpful in improving urban flood response based on deep learning methodology.

• Journal of Korean Society on Water Environment
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• v.34 no.6
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• pp.569-578
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• 2018

To minimize the negative alterations in hydrologic and water quality environment in urban areas due to urbanization, Low Impact Development (LID) techniques are actively applied. In Korea, LID facilities are classified as Non-point Pollution Reduction Facilities (NPRFs), and therefore they are evaluated using the performance evaluation method for NPRFs. However, while LID facilities are generally installed in small, distributed configuration and mainly work with the infiltration process, the existing NPRFs are installed on a large scale and mainly work with the reservoir process. Therefore, some limitations are expected in assessing both facilities using the same method as they differ in properties. To solve these problems, in this study, a new method for performance evaluation was proposed with focus on bio-retention LID facilities. EPA SWMM was used to reproduce the hydrologic and water quality phenomena in study area, and SWMM-LID module used to simulate TP interception performance by installing a bio-retention cell under various conditions through long-term simulations. Finally, an empirical formula for Load Capture Ratio (LCR) was derived based on storm water interception ratio in the same form as the existing method. Using the existing formula in estimating the LCR is likely to overestimate the performance of interception for non-point pollutants in the extremely low design capacity, and also underestimate it in the moderate and high design capacity.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.855-869
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• 2023

Low Impact Development (LID) technology has been attracting attention as a countermeasure to solve frequent flood damage in urban areas. LID involves recovery of the natural circulation system based on infiltration and storage capacity at the site of rainfall runoff, to protect the aquatic ecosystem from the effects of urbanization. Bioretention as an element of LID technology reduces outflow through storage and infiltration of storm water runoff, and minimizes the effects of non-point pollutants. Although LIDs are being studied extensively, the amount of quantitative research on small watersheds with bioretention has been inadequate. In this study, a bioretention model was constructed in a small watershed using Korea-Low Impact Development Model (K-LIDM), which was conducted quantitative hydrologic analysis. We anticipate that the results of the analysis will be used as reference data for future bioretention research related to watershed characteristics, vegetation type, and soil condition.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.215-226
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• 2018

The purpose of this study is to improve the accuracy of the urban runoff and drainage network analysis by using the observed water level in the drainage network. To do this, sensitivity analysis for major parameters of SWMM (Storm Water Management Model) was performed and parameters were calibrated. The sensitivity of the parameters was the order of the roughness of the conduit, the roughness of the impervious area, the width of the watershed, and the roughness of the pervious area. Six types of scenarios were set up according to the number and types of parameter considering four parameters with high sensitivity. These scenarios were applied to the Seocho-3/4/5, Yeoksam, and Nonhyun drainage basins, where the serious flood damage occurred due to the heavy rain on 21 July, 2013. Parameter optimization analysis based on PEST (Parameter ESTimation) model for each scenario was performed by comparing observed water level in the conduits. By analyzing the accuracy of each scenario, more improved simulation results could be obtained, that is, the maximum RMSE (Root Mean Square Error) could be reduced by 2.41cm and the maximum peak error by 13.7%. The results of this study will be helpful to analyze volume of the manhole surcharge and forecast the inundation area more accurately.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.5
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• pp.1026-1033
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• 2009

In this study, we computed the unit load of nonpoint source for the forest, agricultural, and urban representative region in Anseongchun watershed. In addition, Flow-weighted mean concentration (FWMC) that well represents runoff characteristics of storm water during rainfall, was calculated, and runoff pollutants loading was also examined. FWMCs of 1st rainfall, which runoff coefficient was high, had a tendency higher than those of 2nd rainfall. Based on landuse results, pollutant concentration of the non-urban such as forest and agricultural regions was higher than that of urban region. In case of BOD, runoff pollutants loading was calculated as 1,395, 1,623, 2,268kg/d in 1st rainfall for forest, agricultural, and urban regions, respectively, while runoff loading of 2nd rainfall was 503kg/d in forest), 512kg/d in agricultural, and 898kg/d in urban. By landuses, unit load of the urban as 72.7kg/ha/yr was 12 times higher than that of the agricultural as 6.5kg/ha/yr, and 8 times higher than that of the forest as 9.5kg/ha/yr.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.482-486
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• 2005

불투수지역의 증가에 따른 도시지역의 비점오염원 해석 및 예측은 수자원 관리측면에서 중요성이 증가하고 있다. 그러나, 실측자료의 부족, 오염물질 발생경로의 불명확, 간헐성, 강우 및 유역특성에 따라 오염부하량 및 첨두농도 등의 변화가 심하므로 인하여 연구에 어려움이 많은 실정이다. 이를 극복하기 위해서는 장기적인 자료수집과 국내실정에 맞는 모형개발이 이루어져야 할 것이다. 따라서, 본 연구에서는 초기강우에 의한 수질항목별 오염부하량 및 농도계산이 가능한 ILLUDAS-NPS 모형을 개발하였다. 본 모형은 국내의 도시지역 유출해석에 주로 사용되는 ILLUDAS 모형에 건기 및 우기시의 수질해석 과정들을 추가하여 해석되어 진다. 건기시의 경우 유량 및 수질 계산은 계수지정법을 사용하였으며, 우기시의 경우 유량계산은 기존 ILLUDAS 모형의 알고리즘을 이용하였고, 수질 계산은 일일 오염물 축적법과 쓸림방정식을 적용하여 계산시간별 오염물질 부하량 및 농도 등을 계산하였다. 모형의 검정을 위하여 홍제천 시험유역의 총 3가지 강우사상을 대상으로 검토한 결과 총부하량, 첨두농도, 첨두농도 발생시간 등에서 전반적으로 실측치와 유사한 결과를 얻을 수 있었다. 또한, ILLUDAS-NPS 모형과 SWMM, STORM 등의 기존 도시유출$\cdot$수질 모형들에 의한 결과들의 비교에서 SWMM 모형과 다소의 차이는 있으나 대부분 잘 일치함을 확인할 수 있었다. 추후, 합리적이고 보다 정확한 비점오염 해석을 위하여 도시지역의 건거시 오염물질의 축적율 및 초기강우에 의한 오염물질 쓸림량 등에 관한 실험 및 현장자료 축적이 필요하다.월이 긴 것으로 나타났다. 이러한 현상은 유입수가 저수지로 유입되면서 초기수위가 높은 경우에 운동량이 상대적으로 많이 소멸되기 때문으로 판단된다. 또한 탁수층의 두께도 8월 성층의 경우가 상대적으로 큰 것으로 나타났다. 이는 중층의 8월 수온분포 또는 밀도분포가 상대적으로 균일하기 때문에 연직방향 이송$\cdot$확산이 많이 이루어졌기 때문으로 판단된다.이는 토성간의 침투속도 및 투수속도의 경향이 반영된 것이다. 경사에 따라서는 경사도가 증가할수록 지수적으로 감소하였으며 $10\% 경사일 때를 기준으로 $I(mm)=I_{10}{\times}1.17{\times}e^{-0.0164s(\%)}$로 나타났다. 같은 조건에서 강우량과 유거수의 관계는 $Ro_{10}(mm)=5.32e^{0.11R(mm)}(r^2=0.69)$로 나타났다. 이는 토양의 투수특성에 따라 강우량 증가에 비례하여 점증하는 침투수와 구분되는 현상이었다. 경사와 토양이 같은 조건에서 나지의 경우 역시 $Ro_{B10}(mm)=20.3e^{0.08R(mm)(r^2=0.84)$로 지수적으로 증가하는 경향을 나타내었다. 유거수량은 토성별로 양토를 1.0으로 기준할 때 사양토가 0.86으로 가장 작았고, 식양토 1.09, 식토 1.15로 평가되어 침투수에 비해 토성별 차이가 크게 나타났다. 이는 토성이 세립질일 수록 유거수의 저항이 작기 때문으로 생각된다. 경사에 따라서는 경사도가 증가할수록 증가하였으며 $10\% 경사일 때를 기준으로 $Ro(mm)=Ro_{10