• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.529-536
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• 2013

The semi-distributed rainfall runoff model of SWAT is applied to the Seom-river experimental watershed. The simulations of various antecedent periods before the targeted simulation periods of 2002 to 2009 are not necessary despite of the slight appearance of corresponding changes in simulated total runoff. The simulated results of total runoff by using various numbers of soil layer maps have little differentiated nevertheless the slight changes in simulated results have been appeared. The 7 parameters of CANMX, $CN_2$, ESCO, GW_REVAP, SOL_ALB, SOL_AWC, and SOL_K greatly govern the rainfall runoff are confirmed and their sensitivity analyses have been carried out. The optimal parameters used in SWAT are derived by SUFI-2 of SWAT-CUP. The NS and $R^2$ are 0.99 and 0.98, respectively which is shown the good agreement between the observed and the simulated results. The uncertainty factors of P-factor and R-factor are 0.85 and 0.06, respectively which is also shown the high efficiency of the model. The high applicability is also shown with improving the RMSE in SWAT model simulation using the parameters estimated by SUFI-2 of SWAT-CUP.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.647-659
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• 2003

The purpose of this study is to evaluate hydrological applicability of spatially observed rainfall distribution data by the TRMM/PR (Tropical Rainfall Measuring Mission / Precipitation Radar). For this study, firstly, TRMM/PR data (Y) of the Yongdam-Dam Watershed (930.38$km^2$) was extracted and secondly, TRMM/PR data and the rainfall data (X) by AWS (Automatic Weather Station) were compared by executing a correlation analysis. As a result, the regression equations were deduced as two parts (under 60mm/day : Y = 18.55X-0.53, over 60mm/day : Y = 3.11X+51.16). SCS runoff analysis was conducted using 7 rainfall events in 1999 for Yongdam-Dam watershed and the Cheon-Cheon subwatershed for the revised TRMM/PR data. TRMM/PR data showed relative errors ranging from 19.6％ ti 45.6％, and from 11.3％ to 38.9％ for Cheon-Cheon subwatershed and Yongdam-Dam watershed, respectively, AWS data showed relative errors ranging from 0.5％ to 12.8％, and from -1.6％ to -10.3％, for Cheon-Cheon subwatershed and Yongdam-Dam watershed, respectively. Futher researches are necessary to evaluate the relationship between TRMM/PR data and AWS data for practical hydrological applications.

• Journal of Korea Water Resources Association
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• v.51 no.9
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• pp.747-759
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• 2018

Multivariate regional frequency analysis has advantages of regional and multivariate framework as adopting a large number of regional dataset and modeling phenomena that cannot be considered in the univariate frequency analysis. To the best of our knowledge, the multivariate regional frequency analysis has not been employed for hydrological variables in South Korea. Applicability of the multivariate regional frequency analysis should be investigated for the hydrological variable in South Korea in order to improve our capacity to model the hydrological variables. The current study focused on estimating parameters of regional copula and regional marginal models, selecting the most appropriate distribution models, and estimating regional multivariate growth curve in the multivariate regional frequency analysis. Annual maximum rainfall and duration data observed at 71 stations were used for the analysis. The results of the current study indicate that Frank and Gumbel copula models were selected as the most appropriate regional copula models for the employed regions. Several distributions, e.g. Gumbel and log-normal, were the representative regional marginal models. Based on relative root mean square error of the quantile growth curves, the multivariate regional frequency analysis provided more stable and accurate quantiles than the multivariate at-site frequency analysis, especially for long return periods. Application of regional frequency analysis in bivariate rainfall-duration analysis can provide more stable quantile estimation for hydraulic infrastructure design criteria and accurate modelling of rainfall-duration relationship.

• Journal of the Korean GEO-environmental Society
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• v.6 no.2
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• pp.61-73
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• 2005

In Korea, none of the design methods, which can consider the properties of hard soil, weathered rock and the condition of construction, are suggested. Therefore, the properties of geomaterial are simply classified into three categories such as sand, clay and rock for the resistance estimation of axially loaded drilled shafts in Korea. However, in America, O'Neill et al.(1996) presented design methods for a new category of geomaterial which is between soil and rock termed "intermediate geomaterials, IGM's". And FHWA(1999) adapted above most complete classification of geomaterials in its design manual. However, in Korea, these properties are depended on the engineer's judgement, the weathered rocks may be counted as soils, although they may be referred to as IGM's in America. In this study, the applicability of IGM method was investigated through the two construction sites in Korea. For the comparison, two geomaterial properties are applied, respectively. The one was sound soil condition and the other was IGM condition and classical design method and IGM method were applied, respectively. The results showed that the predicted bearing capacities of drilled shafts with IGM's were larger than the predicted values by the classical design method with sound soil condition.

• Journal of the Korean GEO-environmental Society
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• v.8 no.4
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• pp.47-55
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• 2007

Using the results of the Piezocone Penetration Test (PCPT) which were executed at the Yangsan-Mulgum site, the applicability of the interpretation methods for estimating the coefficient of consolidation ($C_v$) of soft clay was evaluated. At the same time, laboratory soil tests using the total of 172 undisturbed soft clay samples from the 44 regions of the Yangsan-Mulgum site were performed to study the differency in the coefficient of consolidation ($C_v$) compared to the results of PCPT. The calculated constrained modulus ($M_{\varepsilon}$) and coefficient of consolidation ($C_v$) using the results of consolidation laboratory tests which are based upon the consolidation theory of Terzaghi were compared with the predicted constrained modulus ($M_p$) and coefficient of consolidation ($C_{v-{M_p}}$) from the PCPT. The relationship between the predicted constrained modulus ($M_p$) and the calculated constrained modulus($M_c$) were showed good correlation. The $M_p$ by the Jones & Rust method were showed mostly similar to the calculated constrained modulus ($M_c$). The relationship between the coefficient of consolidation ($C_v$) obtained from the consolidation tests and the calculated coefficient of consolidation ($C_{v-{M_p}}$) were showed a linear relationship. The results of the calculated coefficient of consolidation ($C_{v-{M_p}}$) were about 54% of the value of the coefficient of consolidation ($C_v$) obtained from the consolidation tests.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.1
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• pp.1-10
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• 2003

In this paper, the laboratory test results with middle-sired ,soil box test in modeling the in-situ installing of horizontal drains are discussed the estimation of the optimum negative pressure. The test was carried out in the different vacuum pressure conditions together with the measurement for the settlement and volume change of drained water by the installed drains during the consolidation process. After the test, the water content was measured to both directions of lateral distance from the drain and depth of the soil, to find out the distribution of ground improvement and strength enhancement. From the analysis on the distribution of water content, the gradual application of vacuum pressure to higher level by pre-determined stages starting from low vacuum pressure is found to be effective and desirable. In the comparison of the degrees of consolidation with elapsed time, the calculated value by the prediction method based on the Barren's conventional theory showed a good agreement with the measured value. With this, It is positively considered that the applicability of the prediction method based on Barren's theory to the practical design of horizontal drains can be justified such as in the calculation of drain spacing and consolidation period.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.3
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• pp.103-113
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• 2018

Tide-surge characteristics of the West/South domestic coasts were analyzed with a tool of EST (empirical simulation technique). As a result, stations of Incheon, Gunsan, Mokpo and Busan are categorized as tide-dominant coasts, while Yeosu, Tongyoung and Busan are as surge-dominant coasts. In the tide-dominant coasts, extreme sea level of less than 50-yr frequency is formed without typhoon-surge, while only 10-yr extreme sea level is formed in the surge-dominant coasts. As the results of casual condition of extreme sea level formation considering the relative degree of surge on tide, the regional characteristics were detected also. Three methods for estimating the design tide level were compared. The AHHW method shows an unrealistic outcomes of the concern of over estimate design. Furthermore, the probability distribution function method has been concerned as causing missing data if a huge typhoon occurs in a neap tide or a low tide. To cope with these drawbacks, the applicability of the EST method is proved to be suitable especially in tide-dominant coasts.

• Journal of Korea Water Resources Association
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• v.46 no.5
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• pp.519-530
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• 2013

To provide a reliable tool for runoff simulations of ungauged watersheds upstream of reservoirs, a daily runoff simulation model, Tank model, is restructured, the parameter regionalization of the model is conducted, and the model's applicability is evaluated. Taking into account the characteristics of runoffs from the watersheds, a three-tank model is employed. The percolation process of the model's third tank is eliminated, considering the water budgets of the watersheds, and its evapotranspiration component is improved, reflecting the conditions of meteorological observation in South Korea. The sensitivity analysis of the model shows that the model's behaviors, varying with a sensitive parameter, ${\alpha}$, are reasonable. The regional parameter estimation equations are determined, using the characteristics and land uses of the watersheds as variables. The model is applied for the runoff simulations of three watersheds and the water stage simulation of one reservoir, and the simulation results are then compared with the observed values, which prove to be in close agreement with the observations. In addition, the results from simulating inflows of twenty-four reservoirs using the model show that the averages of evapotranspiration rate and runoff rate are 42.8% and 56.6%, respectively, which are resonable. Consequently, it is concluded that the model is practically applicable to simulating runoffs from watersheds upstream of reservoirs, and simulated inflow data are useful for watershed management and reservoir planning, design, and operation.

• Journal of the Korean Society for Railway
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• v.18 no.6
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• pp.543-551
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• 2015

Quick-hardening track (QHT) is a construction method which is used to change from old ballast track to concrete track. Sufficient time for construction is important, as the construction should be done during operational breaks at night. Most of the time is spent on exchanging the ballast layer. If it is possible to apply the ballast non-exchange type of quick-hardening track, it would be more effective to reduce the construction time and costs. In this paper, pouring materials with high permeability are suggested and a construction method involving a layer separation pouring process considering the void condition is introduced in order to develop ballast non-exchange type of QHT. The separate pouring method can secure the required strength because optimized materials are poured into the upper layer and the lower layer for each void ratio condition. To ensure this process, a rheology analysis was conducted on the design of the pouring materials according to aggregate size, the aggregate distribution, the void ratio, the void size, the tortuosity and the permeability. A polymer series was used as the pouring material of the lower layer to secure the void filling capacity and for adhesion to the fine-grained layer. In addition, magnesium-phosphate ceramic (MPC) was used as the pouring material of the upper layer to secure the void-filling capacity and for adhesion of the coarse-grained layer. As a result of a mechanics test of the materials, satisfactory performance corresponding to existing quick-hardening track was noted.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.783-791
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• 2018

The biased estimation of low density rainfall network and radar rainfall has limited application to extreme rainfall in a small area. To improve this, more rainfall information needs to be produced. In this study, we analyzed the applicability of the vehicle rainfall sensor developed and used recently. The developed rainfall sensor was attached to the vehicle to observe the rainfall according to the movement of the vehicle. The analytical method used time series and average rainfall values for observations of rainfall sensors and nearby rainfall stations. The results show that the trend of observed values according to rainfall events shows a certain pattern. It is analyzed that it is caused by various causes such as the difference between the observation position of the rainfall sensor and the nearby rainfall station, the moving speed of the vehicle, and the rainfall observation method. This result shows the possibility of rainfall observation using a rainfall sensor for a vehicle, and it is possible to observe rainfall more precisely through experiments and improvement of rainfall sensors in various conditions in the future.