• Journal of Environmental Science International
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• v.7 no.4
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• pp.451-460
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• 1998

The objectives of this study Is to evaluate the total runoff yield, peak flow and peak flow travel time depending on the urbanization, return period and rainfall patterns at the downstream of Manchon urban watershed in TaeGu City. SWM(Storm Water Management Model) is used for runog analysis based on 5 different steps of urbanization and 4 different types of Hufrs quartile according to 8 return periods. It is analyzed that the order of total runoff yield according to raiun patterns is Huffs 4, Huffs 2. Huffs 3 and Huffs 1 quartile, that of peak flow magnitude is Huffs 2, Huffs 1, Huffs 4 and Huffs 3 quartile at present development ratio. under the 60, 70, 80 and 90ft of urbanization to the 50% of urbanization by means of the rainfall patterns, the mean Increasing ratio of total runoff yield for each case is 4.55, 11.43, 16.07 and 20.02%, that of peak flow is 5.82, 13.61, 17.15 and 18.83%, the mean decreasing ratio of peak flow travel time Is 0.00, 2.44, 5.07 and 6.26%, the mean increasing ratio of runoff depth Is 4.51, 11.42, 16.02 and 20.05% respectively. the mean increasing ratio of total runoff yield by means of each and 19.71%. Therefore, as the result of this study. it can be used for principal data as to storm sewage treatment and flood damage protection planning in urban small watershed.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.107-113
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• 2009

The purpose of this study is to estimate the design flood runoff for ungaged forest watershed to reduce the flood damage in national park. Daewonsa watershed in Jirisan National Park was selected as study watershed, of which characteristic factors were obtained from GIS data. Flood runoff was simulated using SCS unit hydrograph module in HEC-HMS model. SCS Curve Number (CN) was calculated from forest type area weighted average method. Huff's time distribution of second-quartile storm of the Sancheong weather station, which is nearest from study watershed, was used for design flood runoff estimation. Critical storm duration for the study watershed was 3 hrs. Based on the critical duration, the peak runoff for each sub-watershed were simulated. It is recommended to monitor the long-term flow data for major stream stations in National Park for a better reliable peak runoff simulation results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5151-5156
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• 2010

In the previous researches for storm sewer design, the flow paths in overall network were determined to minimize the construction cost and then, it was not considered the superposition effect of runoff hydrographs in the sewer pipes. However, in this research, the flow paths are determined considering the superposition effect to reduce the inundation risk by controlling and distributing the flows in the sewer pipes. This is accomplished by distributing the inflows that enter into each junction by changing the flow path in which pipes are connected between junctions. In this paper, the superposition effect and peak outflows at outlet were analyzed considering the changes of the flow paths in the sewer network. Then, the flow paths are determined using genetic algorithm and the objective function is to minimize the peak outflow at outlet. As the applied result for the sample sewer network, the difference between maximum and minimum peak outflows which are caused by the change of flow path was about 5.6% for the design rainfall event of 10 years frequency with 30 min. duration. Also, the typhoon 'Rusa' which occurred at 2002 was applied to verify the reduction of inundation risk for the excessive rainfall, and then, the amount of overflows was reduced to about 31%.

• Magazine of the Korean Society of Agricultural Engineers
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• v.8 no.1
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• pp.1011-1034
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• 1966

This thesis is the final report which has long been studied by the author to obtain the design basis for various hydrological constructions with the specific system suitable to the natural environmental conditions in Korea. This report is divided into two parts: one is to estimate runoff volume from watersheds and the other to estimate the peak discharge for a single storm. According to the result of observed runoff record from watersheds, it is known that Kajiyama formula is useful instrument in estimating runoff volume from watersheds in this country. But it has been found that this formula shows us 20-30% less than the actual flow. Therefore, when wihed to bring a better result, the watershed characteristics coefficient in this formula, that is, f-value, should be corrected to 0.5-0.8. As for the method to estimate peak discharge from drainage basin, the author proposes to classify it in two ways; one is small size watershed and the other large size watershed. The maximum -flood discharge rate $Q_p$ and time to peak Pt obtained from the observed record on the small size watershed are compared by various methods and formulas which are based upon the modern hydrological knowledge. But it was fou.d that it. was not a satisfied result. Therefore, the author proposes. tocomputate $Q_p$, to present 4.0-5.0% for the total runoff volume ${\Sigma}Q$.${\Sigma}Q$ is computed under the assumption of 30mm 103s in watershed per day and to change the theoritical total flow volume to one hour dura tion total flow rate when design daily storm is given. Time to peak Pt is derived from three parameters which are u,w,k. These are computed by relationship between total runoff volume (ha-m unit)and $Q_p$. (C.M.S. unit). Finally, the author checked out these results obtained from 51 hydrographs and got a satisfied result. Therefore the author suggested the model of design dimensionless unit-hydrograph. And the author believes that this model will be much available at none runoff record river site. In the large size watersheds in Korea when the maximum discharge occurs, the effective rainfall is two consequtive stormy days. So the loss in watershed was assutned as 6Omm/2days,and the author proposed 3-hour-daration hydrograph flow distribution percentage. This distribution percentage will be sure to form the hydrograph coordinate.

• Water for future
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• v.14 no.4
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• pp.27-34
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• 1981

The design flow of the urban strom drainage systems has been assessed largely on a basis of empirical relations between rainfall and runoff, and the rational formula has been widely used for the cities in our country. In order to estimate it more accurately, the urban runoff simulation model based on the RRl method has been developed and applied to the sample basin in this study. The rainfall hyetograph of the design stromfor the design flow has been obtained by the determination of the total rainfall and the temporal distributions of that rainfall. The total rainfall has been assessed from the empirical formula of rainfall intensity and the temporal distribution of that rainfall determined on the basis of Huff's method from the historical rainfall data of the basin. The virtual inflow hydrograph to each inlet of the basin has been constructed by computing the series of discharges in each time increment, using design strom hyetograph and time-area diagram. The actual runoff hydrograph at the basin outlet has been computed from the virtual inflow hydrographs by developing a relations between discharge and storage for the watershed. The discharge data for verification of the simulated runoff hydrograph are not available in the sample basin and so the sensitivity analysis of the simulation model has not been possible. The peak discharge for the design of drainage systems has been estimated from the computed runoff hydrograph at the basin outlet and compared to thatl obtained form the rational formula.

• Journal of Korea Water Resources Association
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• v.51 no.6
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• pp.491-501
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• 2018

This study presents a systematic framework to derive the best values of design and planning parameters for low impact development (LID) practices. LID was developed to rehabilitate the distorted hydrological cycle due to the rapid urbanization. This study uses Water Management Analysis Module (WMAM) to perform sensitivity analysis and multiple scenario analysis for LID design and planning parameters of Storm Water Management Model (SWMM). This procedure was applied to an urban watershed which have experienced rapid urbanization in recent years. As a result, the design and planning scenario derived by WMAM shows lower total flows and peak flow, and larger infiltration than arbitrary scenarios for LID design and planning parameters. In the future, economic analysis can be added for this application in the field.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.58-68
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• 2009

Low impact development (LID) technique is relatively new concept to reduce surface runoff and pollutant loading from land cover by attempting to match predevelopment condition with various integrated management practices (IMPs). In this study, computational model for designing and evaluating LID, named LIDMOD, was developed based on SCS-CN method and applied at Andong bus terminal to evaluate LID applicapability and design retention/detention area for volume or peak flow control. LIDMOD simulated with 21 years simulation period that yearly surface runoff by post-development without LID was significantly higher than that with LID showing about 2.8 times and LID could reduce efficiently yearly surface runoff with 75% reduction of increased runoff by conventional post development. LIDMOD designed detention area for volume/peak flow control with 20.2% of total area by hybrid design. LID can also efficiently reduce pollutant load from land cover. Pollutant loads from post-development without LID was much higher than those from pre-development with showing 37 times for BOD, 2 times for TN, and 9 times for TP. Pollutant loads from post-development with LID represented about 57% of those without LID. Increasing groundwater recharge reducing cooling and heating fee, creating green refuge at building area can be considered as additional benefits of LID. At the point of reducing runoff and pollutant load, LID might be important technique for Korean TMDL and LIDMOD can be useful tool to calculate unit load for the case of LID application.

• Journal of Korea Water Resources Association
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• v.44 no.10
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• pp.777-786
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• 2011

In the previous researches for storm sewer design, the flow path, pipe diameter and pipe slope were determined to minimize the construction cost. But in the sewer networks, the flows can be changed according to flow path. The current optimal sewer layout models have been focussed on satisfying the design inflow for sewer designs, whereas the models did not consider the occurrences of urban inundation from excessive rainfall events. However, in this research, the sewer networks are determined considering the superposition effect to reduce the inundation risk by controlling and distributing the inflows in sewer pipes. Then, urban inundation can be reduced for excessive rainfall events. An Optimal Sewer Layout Model (OSLM) was developed to control and distribute the inflows in sewer networks and reduce urban inundation. The OSLM uses GA (Genetic Algorithm) to solve the optimal problem for sewer network design and SWMM (Storm Water Management Model) to hydraulic analysis. This model was applied to Hagye basin with 44 ha. As the applied results, in the optimal sewer network, the peak outflow at outlet was reduced to 7.1% for the design rainfall event with 30 minutes rainfall duration versus that of current sewer network, and the inundation occurrence was reduced to 24.2% for the rainfall event with 20 years frequency and 1 hour duration.

• Journal of Korean Society on Water Environment
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• v.34 no.4
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• pp.382-390
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• 2018

In this study, the LIDMOD3 was developed to design and evaluate low impact development (LIDMOD). In the same fashion, the LIDMOD3 employs a curve number (NRCS-CN) method to estimate the surface runoff, infiltration and event mean concentration as applicable to pollutant loads which are based on a daily time step. In these terms, the LIDMOD3 can consider a hydrologic soil group for each land use type LID-BMP, and the applied removal efficiency of the surface runoff and pollutant loads by virtue of the stored capacity, which was calculated by analyzing the recorded water balance. As a result of Model development, the LIDMOD3 is based on an Excel spread sheet and consists of 8 sheets of information data, including: General information, Annual precipitation, Land use, Drainage area, LID-BMPs, Cals-cap, Parameters, and the Results. In addition, the LIDMOD3 can estimate the annual hydrology and annual pollutant loads including surface runoff and infiltration, the LID efficiency of the estimated surface runoff for a design rainfall event, and an analysis of the peak flow and time to peak using a unit hydrolograph for pre-development, post-development without LID, and as calculated with LID. As a result of the model application as applied to an apartment, the LIDMOD3 can estimate LID-BMPs considering a well spatical distributed hydroloic soil group as realized on land use and with the LID-BMPs. Essentially, the LIDMOD3 is a screen level and simple model which is easy to use because it is an Excel based model, as are most parameters in the database. This system can be expected to be widely used at the LID site to collect data within various programmable model parameters for the processing of a detail LID model simulation.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.1-7
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• 2009

Most developed models are designed to determine pipe diameter, slope and overall layout in order to minimize the cost for the design rainfall for the optimal sewer layout. However, these models are not capable of considering the superposition effect of runoff hydrographs in the sewer pipes. The flow characteristics in the sewer pipes, such as the sewer layout, pipe diameter and slope, vary according to the design of the sewer system. In particular, when the sewer network is modified, the shapes of the runoff hydrographs in the sewer pipes also change because of the superposition effect. In this study, the sewer layout is designed to control and distribute the flows in the sewer pipes, while considering the runoff superposition effect, in order to reduce the inundation risk at each junction. This is accomplished by separating the inflows that enter into each junction by changing the way in which pipes are connected between junctions. And this model combines SWMM (Storm Water Management Model) to perform the hydraulic analysis for the flows in the sewer network. The current sewer layout was modified to minimize the peak outflow at outlet in Garak basin, Seoul, South Korea. As the results, the peak outflows at the outlet were decreased by approximately 20% for the design rainfall during 30 minutes and the total overflows were also decreased for the excessive rainfalls.