• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.549-560
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• 2010

Recently, heavy rainfalls due to the climate change in Korea have caused inundation problems in urban sewer networks. In july 2006, a flooding accident at Misari motorboat racing stadium near the Han river occurred due to the effect of record-breaking outflow discharge from Paldang-dam. The purpose of this study was to simulate and analyze the flooding accident at Misari stadium by MOUSE model. The results of simulation analysis indicated that the total flood volume was $1,313,450m^3$. The effect of back water was 85.9% of the total volume which was caused by the manhole accident, and the effect of accumulated runoff was 14.1% of total volume which was caused by non-return valve shutdown. The simulation results of this MOUSE modeling that was linked to the boundary condition of the dynamic flows in the river by DWOPER model showed the potential of successful inundation analysis for sewer networks.

• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.935-946
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• 2006

This study proposed a new procedure of sustainable water resources planning to prevent the urban streamflow depletion, based on the Heathcote's study in 1998: (1) to understand the watershed component and processes, (2) to identify and quantify problems within the watershed, (3) to set clear and specific goals, (4) to develop a list of management options, (5) to eliminate infeasible options, (6) to test the effectiveness of remaining feasible options, and (7) to develop the final options. PSR(Presure-State-Response) concept was used for the determination of indicators of PSD(Potential Streamflow Depletion; step 2) and effect equation (step 7) and composite programming for the calculation of PSD. The instreamflow requirement was proposed as clear and specific goal (step 3) and was determined by the larger of the PHABSIM's environmental flow and the drought flow. A continuous rainfall-runoff model is necessary to test the effectiveness of alternatives. It should estimate not only the exact runoff but also the effect of landuse change, reservoir, infiltration facility and so on like SWAT(Soil and Water Assessment Tool). The proposed procedure will be applied on the corresponding paper.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.5
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• pp.569-577
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• 2019

Urban flooding has been a frequent phenomenon in recent years caused by the increase in maximum stormwater runoff arising from abnormal rainfall due to global warming, urban development, and development of lowlands according to population inflows. In order to respond positively against abnormal precipition in the city, it is necessary to check the GWI (Green Water Infra) effect and effectively utilize the existing stormwater detention tanks and treat stormwater to prevent local flooding. In this study, Overflow Type stormwater drainage methods are evaluated as a method of preventing urban flooding in abnormal precipitation using the Dynamic Wave Analysis SWMM (Storm Water Management Model) provided by the United States Environmental Protection Agency. Comparing and analyzing the Upward Watergate Type and Overflow Type, it was analyzed that the Overflow Type reduces the maximum flood discharge by 61 % and the total flood volume by 56 % in the rainfall of Typhoon Kong-rey. The application of the Overflow Type and the natural-pneumatic drainage method to the rainfall of Typhoon Soulik resulted in a 20 % reduction in maximum flood runoff and a 67 % reduction in total flood quantity. Therefore, as a solution to the abnormal rain fall, it is possible to improve the existing stormwater detection tank and install additional facilities. It is expected to be economically possible to strom drainage under limited conditions.

• Journal of Korea Water Resources Association
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• v.53 no.12
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• pp.1183-1192
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• 2020

Economic analysis is a basic step in establishing disaster mitigation measures, but it is difficult to verify the results due to uncertainty. Therefore, the scope of investigation and analysis is wide. However, it is difficult to predict the amount of damage caused by flooding because the collection of relevant data is limited in the ungauged basin. In this study, distributed runoff analysis and flooding analysis were performed, and a method of estimating the amount of flood damage in the ungauged basin was proposed using collectible social and economic indicators and flood analysis results. For distributed runoff analysis and flooding analysis, GRM (Grid based Rainfall-runoff Model) and G2D (Grid based 2-Dimensional land surface flood model) developed by Korea Institute of Civil engineering and Building Technology were used. The method of substituting collectible social and economic indicators into the simple method and improvement method was used to estimate the amount of flood damage. As a result of the study, it was possible to estimate the amount of flood damage using satellite data and social and economic indicators in the ungauged basin.

• Journal of Korean Society of Disaster and Security
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• v.14 no.2
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• pp.1-11
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• 2021

Recently, in Korea, the risk of meteorological disasters is increasing due to climate change, and the damage caused by rainfall is being emphasized continuously. Although the current weather forecast provides quantitative rainfall, there are several difficulties in predicting the extent of damage. Therefore, in order to understand the impact of damage, the threshold rainfall for each watershed is required. The damage caused by rainfall occurs differently by region, and there are limitations in the analysis considering the characteristic factors of each watershed. In addition, whenever rainfall comes, the analysis of rainfall-runoff through the hydrological model consumes a lot of time and is often analyzed using only simple rainfall data. This study used GIS data and calculated the threshold rainfall from the threshold runoff causing flooding by coupling two hydrologic models. The calculation result was verified by comparing it with the actual case, and it was analyzed that damage occurred in the dangerous area in general. In the future, through this study, it will be possible to prepare for flood risk areas in advance, and it is expected that the accuracy will increase if machine learning analysis methods are added.

• Journal of Korea Water Resources Association
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• v.51 no.4
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• pp.347-354
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• 2018

In urban areas, runoff flow is drained through sewer networks as well as surface areas. Therefore, it is very important to consider sewer networks as a component of hydrological drainage processes when conducting urban inundation modelling. However, most researchers who have implemented urban inundation/flood modelling, instinctively simplified the sewer networks without the appropriate criteria. In this research, a 1D-2D fully coupled urban inundation model is applied to estimate the influence of sewer network simplification on urban inundation modelling based on the dendritic network classification. The one-dimensional (1D) sewerage system analysis model, which was introduced by Lee et al. (2017), is used to simulate inlet and overflow phenomena by interacting with surface flow. Two-dimensional (2D) unstructured meshes are also applied to simulate surface flow and are combined with the 1D sewerage analysis model. Sewer network pipes are simplified based on the dendritic network classification method, namely the second and third order, and all cases of pipes are conducted as a control group. Each classified network case, including a control group, is evaluated through their application to the 27 July 2011 extreme rainfall event, which caused severe inundation damages in the Sadang area in Seoul, South Korea. All cases are compared together regarding inundation area, inflow discharge and overflow discharge. Finally, relevant criterion for the simplification method is recommended.

• Journal of Korea Water Resources Association
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• v.37 no.3
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• pp.195-206
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• 2004

One of the main factors which reduces the efficiency of a sewage treatment plant is the Inflow/Infiltration(Ⅰ/Ⅰ) in the sewer First we must calculate the quantity of Ⅰ/Ⅰ via the investigation of each sewer to establish the reduction plan of Ⅰ/Ⅰ. However, in Korea, we apply the results of a surveyed sample to the entire study area to establish the reduction plan of Ⅰ/Ⅰ. This methodology just considers the total Ⅰ/Ⅰ for the entire study area but it does not consider the quantity of Ⅰ/Ⅰ for the individual sewer systems. Therefore, we may need the model to consider the Ⅰ/Ⅰ in the individual sewer systems and we develop the model to calculate the Ⅰ/Ⅰ that happen in urban sewer systems. We estimate the Ⅰ/Ⅰ of individual systems by the developed model and the estimated Ⅰ/Ⅰ are utilized as the basic data for the establishment of Ⅰ/Ⅰ reduction plan. The observed Ⅰ/Ⅰ for the entire study area is distributed into the individual sewer systems according to their defect states. Here, the weights of defect elements are calculated using AHP(Analytic Hierarchy Process) and we perform the uncertainty analysis for considering the errors using MCS(Monte Carlo Simulation).

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.105-115
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• 2008

Urbanization results in increased runoff volume and peak flowrate and shortening in time of concentration, which may cause frequent flooding downstream. There are various types of flow retardation methods including detention ponds, retention ponds, and infiltration ponds. In general, hydrologic models to design the detention pond are classified into planning model and design model. This study is comparing and analyzing of planning model to design the detention pond in urban area. Detention ponds data of Disaster Impact Assessment Report on 22 sites were analyzed to investigate proper planning models in this study. From this research, following conclusions are derived, 1) In case of on-line detention pond, Lee model(1991) is the best planning model and similar to real storage volume. 2) In case of off-line detention pond, Abt and Grigg model is much more proper model compared to other models.

• Journal of Korea Water Resources Association
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• v.38 no.10 s.159
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• pp.861-869
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• 2005

A rainfall-runoff model should be calibrated so that the model simulates the hydrological behavior of the basin as accurately as possible. In this study, to calibrate the five parameters of the SSARR model, a multi-objective function and the genetic algorithm were used. The solution of the multi-objective function will not, in general, be a single unique set of parameters but will consist of the so-called Pareto solution according to various trade-offs between the different objectives. The calibration strategy using multi-objective function could decrease calibrating time and effort. From the Pareto solution, a single solution could be selected to simulate a specific flow condition.

• Korean Journal of Hydrosciences
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• v.5
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• pp.33-43
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• 1994

This study is to determine the critical duration of design rainfall and to utilize it for the design of detention pond with pump station. To examine the effect of the duration and temporal distribytion of the design rainfall, Huff's quartile method is used for the 9 cases of durations (ranges from 20 to 240 minutes) with ten years return period, and the ILLUDAS model is used for runoff analysis. The storage ratio, which is the ratio of maximum storage amounts to total runoff volume, is introduced to determine the criticalduration of design rainfall. The duration which maximizes the storage ratio is adopted as the critical duration. This study is applied to 18 urban drainage watercheds with pump station in Seoul, of which the range of watershed area is 0.24~12.70$km^2$. The result of simulation shows that the duration which maximizes storage ratio is 30 and 60 minutes on the whole. It is also shown that the storage ratios of 2nd - and 3rd-quartile pattern are larger than those of 1st- and 4th-quartile pattern of temporal distribution. A simplified empirical formula for Seoul area is suggested by the regression analysis between the maximum storage ratio and the peak ratio. This formula can be utilized for the preliminary design and planning of detention pond with pump station.