• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.937-942
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• 2005

It is necessary to estimate the runoff hydrograph and peak flood discharge using law of probability for synthetic flood control policy and design of hydraulic structures. Rainfall analysis is needed in the process of peak flood discharge estimation and the time distribution of a design rainfall is a very important process in the analysis. In this study, we estimate design flood for a small urban basin and a rural basin of medium scale which have different travel times. The Huff method is widely used in Korea for the time distribution of design rainfall to estimate design flood. So, we use Huff method and a conceptual method which is suggested in this study for the comparative purpose. The 100-year frequency rainfall is used to estimate design flood for each basin and the design flood is compared with the existing design flood. As the result, the design flood is overestimated $14.6m^3/sec$ by Huff method and is underestimated $70.9m^3/sec$ by a conceptual method for the rural basin. For the small urban basin, the design flood is excessively overestimated $294.65m^3/sec$ by Huff method and is overestimated $173m^3/sec$ by a conceptual method. The reason of excessive overestimation by Huff method in the small urban basin is that the increased rate of rainfall intensity according to the decrease of duration is large and the duration exceeds the time of concentration when the increased rainfall intensity is concentrated in a quartile. Therefore, we suggested a conceptual method for the time distribution of design rainfall by considering the rainless period and duration. Especially, the conceptual method might be useful for the small urban basin with short concentration time which the design flood is overestimated by Huff method.

• Journal of Korea Water Resources Association
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• v.41 no.6
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• pp.605-617
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• 2008

This study developed a flood index which evaluates runoff characteristics. Runoff characteristics expressed in a hydrograph were reflected in the flood index in the form of characteristic factors such as a rising curve gradient, a peak discharge, a flood response time, and a flood discharge volume prior to peak. This study applied the standardization method to estimate the relative severity of the characteristic factors by transforming the distribution of characteristic factors into the standard normal distribution. The flood index developed in this study is a comprehensive flood index (CFI) which makes up for the weak points of a flash flood index (FFI) in determining relative severities. The CFI was applied to Han River basin and Selma River basin, and was compared with the FFI based on the correlation analysis and the regression analysis. The CFI could comprehensively evaluate flood runoff characteristics because the CFI is not dominated by a specific characteristic factor, and the CFI could explain more efficiently the relationship between rainfall and runoff than the FFI.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.483-486
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• 2003

This paper presents how effective the detention storage is to control floods at a test watershed. HEC-HMS model was applied to simulate the effects of the storages of different levels and installation methods on the flood peak reduction. The results showed that the detention storage may significant reduce the flood peaks, and the effectiveness depends on the sizes of the storage and types of installation. The simulated peak values reduce considerably for the design storm events. The results also showed that alternatives to control flood may be evaluated using the model.

• Journal of Environmental Science International
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• v.22 no.9
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• pp.1079-1088
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• 2013

The objective of this paper is compare to landuse type for calculating peak flood and soil loss in rapidly expansion urban area. This study compares two landuse maps, including numerical landuse map and aerial photograph landuse map, for calculating the ratio of urban and agriculural area, curve number, time of concentration, peak flood discharge, and soil loss. It is found that flood discharge calculated using aerial photograph landuse map are larger than that calculated using numerical landuse map, and soil loss calculated using aerial photograph landuse map are smaller than that calculated using numerical landuse map. Results also indicate that landuse chage in rapidly expansion urban area significantly influences flood discharge and soil loss.

• Water for future
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• v.19 no.3
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• pp.267-276
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• 1986

This study aims at the development of flood runoff model by comparing and analyzing nonlinear models with linear models in rier basins. The models which are used at the analysis are Nash model and Runoff function method as linear models, and Tank model and Storage function method as nonlinear models. The results, which are obtained from the analysis of these models by using hydrologic data of a representative basin in Nakdong river, Wi-chun basin, show that the peak time, peak flow and flood hydrogrphs by nonlinear models are better than those by linear models in comparison with observed ones, and that nonlinear models are suittable as flood runoff model.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.701-709
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• 2000

Integrated storage function model (ISFM) is applied to some rainfall-runoff events of the selected basins in Korea to show validity of the proposed model. Comparing the numerical results of the model with the field measurements, the simulated hydrographs and peak flood discharges for the most part showed good agreements, except the occurrence time of the peak discharges which showed a bit discrepancy, and they showed it was very hard to have a sufficient lead-time to forecast the flood when the upstream inflow of the channel reach was more dominant than the inflow from the residual watershed of the channel.hannel.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.6
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• pp.119-127
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• 2003

This paper documents recent efforts to validate the GIS-based hydrologic models, HEC-HMS and HEC-GeoHMS by the US Army Corps of Engineers. HMS and Geo-HMS were used to simulate storm runoff from a small rural watershed, the Balan HS#6. The watershed is 3.85 $\textrm{km}^2$ in size. The watershed topographic, soils, and land use data were processed using the GIS tool fur the models. Input parameters were retrieved and calibrated with the field data. The simulated peak runoff, time to peak, and total direct runoff fer twenty three storms were compared with the observed data. The results showed that the coefficient of determination($R^2$) for the observed peak runoff was 0.95 and an error, RMSE, 3.08 $\textrm{m}^3$/s for calibration stages. In the model verifications, $R^2$ was 0.89 and RMSE 6.79 $\textrm{m}^3$/s, which were slightly less accurate than the calibrated data. The simulated flood hydrographs were well compared to the observed. It was concluded that HMS and GeoHMS are applicable to flood analyses for rural watersheds.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.75-83
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• 2013

PURPOSES: In this study, flood mitigation effect of drainage asphalt concrete pavement were analyzed by a SWMM 5.0 program in order to evaluate the low impact development (LID) based on the drainage asphalt concrete pavements. METHODS: In order to determine the porosity parameters of drainage asphalt concretes, the specimen mixtures were manufactured using the conditions presented in the previous study. The numerical simulation was conducted using the SWMM 5.0 program considering the flood mitigation effect of drainage asphalt concrete pavements. The effect of flood reduction can be observed when drainage asphalt concrete pavements were applied to Mokgamcheon watershed. The flood mitigation effect analysis of Mokgamcheon watershed as well as continuous simulation of subwatershed runoff were performed through this study. RESULTS : The analysis of drainage asphalt concrete pavements was carried out for evaluating the effect on runoff, resulting in: the peak flow decreases up to 1.26~9.53% after drainage asphalt concrete pavements applied in the SWMM 5.0 program furthermore, the discharge decreases up to 0.55~4.11%. CONCLUSIONS: As a result, the reduced peak flow and discharge were found through the SWMM 5.0 program. It can be concluded that the flood is effectively reduced when the drainage asphalt concrete pavements are used.

• Journal of Korean Society on Water Environment
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• v.29 no.1
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• pp.45-54
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• 2013

This study analyzes the reduction effects of runoff and flood damage through different arrangements of stormwater storage facilities. Three scenarios based on the spatial allocation of storage capacity are used: concentrated, decentralized and combinative. The characteristics of runoff and flood damage by scenario are compared. The XP-SWMM model is used for runoff simulation by the probable rainfall of return period. The result shows that the concentrated arrangement of storage facilities is most effective to reduce the amount of peak flow and to delay the time of peak flow. Yet, while the concentrated arrangement is most effective to reduce the inundation damage, it is not effective to reduce runoff volume. The decentralized arrangement is most effective to reduce runoff volume. The combinative arrangement is effective not only the runoff reduction but also the reduction of flood damage. The result indicates that the flood mitigation strategies against heavy rainfall need to consider decentralized on-site arrangement for the reduction of runoff volume along with concentrated off-site arrangement of storage facilities.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.87-101
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• 1990

The purpose of this study is to estimate the flood discharge and runoff volume at a stream by using geomorphologic parameters obtained from the topographic maps following the law of stream classification and ordering by Horton and Strahier. The present model is modified from Cheng' s model which derives the geomorphologic instantaneous unit hydrograph. The present model uses the results of Laplace transformation and convolution intergral of probability density function of the travel time at each state. The stream flow velocity parameters are determined as a function of the rainfall intensity, and the effective rainfall is calculated by the SCS method. The total direct runoff volume until the time to peak is estimated by assuming a triangular hydrograph. The model is used to estimate the time to peak, the flood discharge, and the direct runoff at Andong, Imha. Geomchon, and Sunsan basin in the Nakdong River system. The results of the model application are as follows : 1.For each basin, as the rainfall intensity doubles form 1 mm/h to 2 mm/h with the same rainfall duration of 1 hour, the hydrographs show that the runoff volume doubles while the duration of the base flow and the time to peak are the same. This aggrees with the theory of the unit hydrograph. 2.Comparisions of the model predicted and observed values show that small relative errors of 0.44-7.4% of the flood discharge, and 1 hour difference in time to peak except the Geomchon basin which shows 10.32% and 2 hours respectively. 3.When the rainfall intensity is small, the error of flood discharge estimated by using this model is relatively large. The reason of this might be because of introducing the flood velocity concept in the stream flow velocity. 4.Total direct runoff volume until the time to peak estimated by using this model has small relative error comparing with the observed data. 5.The sensitivity analysis of velocity parameters to flood discharge shows that the flood discharge is sensitive to the velocity coefficient while it is insensitive to the ratio of arrival time of moving portion to that of storage portion of a stream and to the ratio of arrival time of stream to that of overland flow.