• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.474-481
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• 2007

With population growth, industrialization, and urbanization within the watershed, the hydrologic response changed dramatically, resulting in increases in peak flow with lesser time to peak and total runoff with shortened time of concentration. Infiltration is directly affected by initial soil moisture condition, which is a key element to determine runoff. Influence of the initial soil moisture condition on hydrograph analysis should be evaluated to assess land use change impacts on runoff and non-point source pollution characteristics. The Long-Term Hydrologic Impact Assessment (L-THIA) model has been widely used for the estimation of the direct runoff worldwide. The L-THIA model was applied to the Little Eagle Creek (LEC) watershed and Its estimated direct runoff values were compared with the BFLOW filtered direct runoff values by other researchers. The $R^2$ value Was 0.68 and the Nash-Sutcliffe coefficient value was 0.64. Also, the L-THIA estimates were compared with those separated using optimized $BFI_{max}$ value for the Eckhardt filter. The $R^2$ value and the Nash-Sutcliffe coefficient value were 0.66 and 0.63, respectively. Although these higher statistics could indicate that the L-THIA model is good in estimating the direct runoff reasonably well, the Antecedent Moisture Condition (AMC) was not adjusted in that study, which might be responsible for mismatches in peak flow between the L-THIA estimated and the measured peak values. In this study, the L-THIA model was run with AMC adjustment for direct runoff estimation. The $R^2$ value was 0.80 and the Nash-Sutcliffe coefficient value was 0.78 for the comparison of L-THIA simulated direct runoff with the filtered direct runoff. However there was 42.44% differences in the L-THIA estimated direct runoff and filtered direct runoff. This can be explained in that about 80% of the simulation period is classified as 'AMC I' condition, which caused lower CN values and lower direct runoff estimation. Thus, the coefficients of the equation to adjust CN II to CN I and CN III depending on AMC condition were modified to minimize adjustments impacts on runoff estimation. The $R^2$ and the Nash-Sutcliffe coefficient values increase, 0.80 and 0.80 respectively. The difference in the estimated and filtered direct runoff decreased from 42.44% to 7.99%. The results obtained in this study indicate the AMC needs to be considered for accurate direct runoff estimation using the L-THIA model. Also, more researches are needed for realistic adjustment of the AMC in the L-THIA model.

• Journal of Korea Water Resources Association
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• v.51 no.1
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• pp.19-33
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• 2018

This study proposed a rainfall-runoff model for the purpose of real-time flood warning in urban basins. The proposed model was based on the shot noise process, which is expressed as a sum of shot noises determined independently with the peak value, decay parameter and time delay of each sub-basin. The proposed model was different from other rainfall-runoff models from the point that the runoff from each sub-basin reaches the basin outlet independently. The model parameters can be easily determined by the empirical formulas for the concentration time and storage coefficient of a basin and those of the pipe flow. The proposed model was applied to the total of three rainfall events observed at the Jungdong, Guro 1 and Daerim 2 pumping stations to evaluate its applicability. Summarizing the results is as follows. (1) The unit response function of the proposed model, different from other rainfall-runoff models, has the same shape regardless of the rainfall duration. (2) The proposed model shows a convergent shape as the calculation time interval becomes smaller. As the proposed model was proposed to be applied to urban basins, one-minute of calculation time interval would be most appropriate. (3) Application of the one-minute unit response function to the observed rainfall events showed that the simulated runoff hydrographs were very similar to those observed. This result indicates that the proposed model has a good application potential for the rainfall-runoff analysis in urban basins.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.237-247
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• 2018

The basin characteristics reflect the attributes of geomorphological pattern of basin and stream networks affect the rainfall-runoff. In order to analyze the relationship between the basin runoff and stream morphometric characteristics, the morphometric characteristics were investigated for 27 water-level observation stations on 19 rivers in the Han River basin using Arc-map. The morphometric characteristics were divided into linear, areal and relief aspects for calculation while the annual mean runoff ratio as a basin response by rainfall was estimated using the measured precipitation and discharge to analyze the rainfall-runoff characteristics. The correlation among the morphometric parameters were schematized to analyze the correlations among them. The multiple regression equation for rainfall-runoff ratio was provided with morphometric parameters of stream length ratio, form factor ratio, shape factor, stream area ratio, and relief ratio and the coefficient of determination was 0.691. The RMSE and MAPE between the measured and the estimated annual runoff rates were found as 0.09, 11.61% respectively, the suggested regression equation showed good estimation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1458-1464
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• 2011

This study is on the application of TOPMODEL-topographic based hydrologic model-to the runoff analysis, The test area was the ssang-chi watershed which is mountainous catchment located in the upstream of the sumjin-gang basin and the watershed area is $126.7km^2$. The six's hourly runoff and precipitation data was selected in the 2006 ~ 2009 year. And the model parameters are calibrated using observed runoff data by Pattern Search method. The topographic index of the ssang-chi catchment was produced by digital elevation model(DEM) of 100m grid. As a results of the analysis, the parameters of model, a decay facter(m), transmissivity(T0), and the unsaturated zone delay(TD) are sensible to hydrologic response, and the simulated runoff data are in good agreement with observed runoff data.

• Journal of Korea Water Resources Association
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• v.38 no.2
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• pp.167-177
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• 2005

In this study, the PRMS(Precipitation and Runoff Modeling System), developed by USGS(United States Geological Survey), was applied to the Yongdam dam watershed in the Geum River basin. The efficiency for runoff simulation and spatial characteristics of PRMS were evaluated. The runoff changes with the changes of subcatchments and HRUs were estimated. As results, the size of the subcatchment and HRV did not significantly affect the runoff at the exit of watershed. Consequently, the spatial characteristic of PRMS was shown as lumped type rather than semi-distributed. The geographical input data for Yongdam dam watershed were converted to the USGS Input type, and the parameters were calibrated using Rosenbrock optimization method, validated with the observed runoff data. The PRMS showed resonable agreements in the long-term continuous runoff simulation, if the accuracy of observed data is ensured.

• Journal of The Geomorphological Association of Korea
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• v.28 no.2
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• pp.31-44
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• 2021

Due to recent climate change, continuous soil loss is occurring in the mountainous watershed. The development of geographic information systems allows the spatial simulation of soil loss through hydrological models, but more researches applied to the mountain watershed areas in Korea are needed. In this study, prior to simulating the soil loss characteristics of the mountainous watershed, the field monitoring and the SWAT and GeoWEPP models were used to simulate and analyze the rainfall and runoff characteristics in the mountainous watershed area of Jirisan National Park. As a result of monitoring, runoff showed a characteristic of a rapid response as rainfall increased and decreased. In the simulation runoff results of calibrated SWAT models, R², RMSE and NSE was 0.95, 0.03, and 0.95, respectively. The runoff simulation results of the GeoWEPP model were evaluated as 0.89, 0.30, and 0.83 for R², RMSE, and NSE, respectively. These results, therefore, imply that the runoff simulated through SWAT and GeoWEPP models can be used to simulate soil loss. However, the results of the two models differ from the parameters and base flow of actual main channel, and further consideration is required to increase the model's accuracy.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.5
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• pp.537-543
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• 2006

There have been many recent studies on the nonlinear rainfall-runoff modeling, where the use of neural networks is shown to be quite successful. Due to fundamental limitation of linear structures, employing linear models has often been considered inferior to the neural network approaches in this area. However, we believe that with an appropriate extension, the concept of linear impulse responses can be a viable tool since it enables us to understand underlying dynamics principles better. In this paper, we propose the use of multiple impulse responses for the problem of rainfall-runoff analysis. The proposed method is based on a simple and fixed strategy for switching among multiple linear impulse-response models, each of which satisfies the constraints of non-negativity and uni-modality. The computational analysis performed for a certain Korean hydrometeorologic data set showed that the proposed method can yield very meaningful results.

• Water Engineering Research
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• v.6 no.2
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• pp.91-99
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• 2005

One of the most important factors for estimating a flood runoff from streams is the lag time. It is well known that the lag time is affected by the morphometric properties of basin which can be expressed by catchment shape descriptors. In this paper, the notion of the geometric characteristics of an equivalent ellipse proposed by Moussa(2003) was applied for calculating the lag time of geomorphologic instantaneous unit hydrograph(GIUH) at a basin outlet. The lag time was obtained from the observed data of rainfall and runoff by using the method of moments and the procedure based on geomorphology was used for GIUH. The relationships between the basin morphometric properties and the hydrological response were discussed based on application to 3 catchments in Korea. Additionally, the shapes of equivalent ellipse were examined how they are transformed from upstream area to downstream one. As a result, the relationship between the lag time and descriptors was shown to be close, and the shape of ellipse was presented to approach a circle along the river downwards. These results may be expanded to the estimation of hydrological response of ungauged catchment.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.57-66
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• 2007

The purpose of this study is both the variation of hydrologic topographical informations extracted by using WMS and the quantitative effect of rainfalll-runoff simulation due to dividing watershed. Miho stream basin in Geum river was selected by this study. Watershed dividing method are determined by area, channel slope and channel length. Hydrological response of divided watershed using Clark method, SCS method and Snyder method was compared with actual measured flood hydrograph. As a results, area-based watershed dividing method are particularly suitable the hydrologic applications using SCS method. This study can be used as basic data for the phase of the runoff variation in Miho stream basin.

• Journal of Korea Water Resources Association
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• v.36 no.5
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• pp.851-861
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• 2003

Snow accumulation and snow melt was simulated and included in the computation of the watershed runoff for Soyanggang Dam and Chungju Dam. A modified Tank Model was used for the simulation, which has three serial tanks and a pulse response function. The model parameters were estimated through the global optimization method of Shuffled Complex Evolution-University of Arizona (SCE-UA). A watershed was divided into four zones of elevation. The temperature decrease of the zones was a rate of -0.6$^{\circ}C$/100m. Almost all precipitation from December to February become accumulated as snow, and then the snow melts and runs off from March to April. The average runoff with snow melt was greater than the average runoff without snow melt during the period from March to April. The improved amount from snow melt simulation was about one fifth of the observed one for Soyanggang Dam. The increased amount for Chungju Dam was about one fourth of the observed average runoff during the same period. Although the watershed runoff was simulated including snow melt, it was less than the observed one for both of the dams.