• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.965-974
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• 2013

Multiple debris flows occurred on July 27, 2012 in Mt. Umyeon, which resulted in 16 casualties and severe property demage. Accurate reproducing of the propagation and deposition of debris flow is essential for mitigating these disasters. Through applying FLO-2D model to these debris flows and comparing the results with field observations, we seek to evaluate the performance of the model and to analyse the rheological model parameters. Representative yield stress and dynamic viscosity back-calculated for the debris flows in the northern side of Mt. Umyeon are 1022 Pa and 652 $Pa{\cdot}s$, respectively. Numerical results obtained using these parameters reveal that deposition areas of debris flows in Raemian and Shindong-A regions are well reproduced in 63-85% agreement with the field observations. However, the propagation velocities of the flows are significantly underestimated, which is attributable to the inherent limitations of the model that can't take the entrainment of bed material and surface water into account. The debris flow deposition computed in Hyeongchon region where the entrainment is not significant appears to be in very good agreement with the field observation. The sensitivity study of the numerical results on model parameters shows that both sediment volume concentration and roughness coefficient significantly affect the flow thickness and velocity, which underscores the importance of careful selection of these model parameters in FLO-2D modeling.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.29-41
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• 2017

Design rainfalls are one of the most important hydrologic data for river management, hydraulic structure design and risk analysis. The design rainfalls are first estimated by a point frequency analysis and the IDF (intensity-duration-frequency) curve is then constructed by a nonlinear regression to either interpolate or extrapolate the design rainfalls for other durations which are not used in the frequency analysis. It has been widely recognised that the more reliable approaches are required to better account for uncertainties associated with the model parameters under circumstances where limited hydrologic data are available for the watershed of interest. For these reasons, this study developed a hierarchical Bayesian based GLM (generalized linear model) for a regional frequency analysis in conjunction with a scaling function of the parameters in probability distribution. The proposed model provided a reliable estimation of a set of parameters for each individual station, as well as offered a regional estimate of the parameters, which allow us to have a regional IDF curve. Overall, we expected the proposed model can be used for different aspects of water resources planning at various stages and in addition for the ungaged basin.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.4
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• pp.217-224
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• 2014

Cochlodinium polykrikoides is a typical harmful algal species which generates the red-tide in the coastal zone, southern Korea. Accurate algal growth model can be established and then the prediction of the red-tide occurrence using this model is possible if the information on the optimal growth model parameters are available because it is directly related between the red-tide occurrence and the rapid algal bloom. However, the limitation factors on the algal growth, such as light intensity, water temperature, salinity, and nutrient concentrations, are so diverse and also the limitation function types are diverse. Thus, the study on the algal growth model development using the available laboratory data set on the growth rate change due to the limitation factors are relatively very poor in the perspective of the model. In this study, the growth model on the C. polykrikoides are developed and suggested as the optimal model which can be used as the element model in the red-tide or ecological models. The optimal parameter estimation and an error analysis are carried out using the available previous research results and data sets. This model can be used for the difference analysis between the lab. condition and in-situ state because it is an optimal model for the lab. condition. The parameter values and ranges also can be used for the model calibration and validation using the in-situ monitoring environmental and algal bloom data sets.

• Journal of Korea Water Resources Association
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• v.47 no.12
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• pp.1155-1163
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• 2014

The complementary relationship-based evapotranspiration models, namely, AA model of Brutsaert and Stricker (1979) and the CRAE model of Morton (1983) was applied to two permanent stream watersheds Jeju island for the first time, and their major optimal parameters were suggested in this study. The representative watersheds for model calibration and validation were selected as the Hancheon watershed located in the northern part of the Jeju island and and the Kangjeongcheon watershed in southern Jeju island, respectively. The estimated actual evapotranspiration for the Hancheon watershed was compared with the result by the hydrological model, and the major parameters of the AA and CRAE models were calibrated until their results match the hydrological simulations. Through the iterative estimations, the optimal parameters were determined as ${\alpha}=1.00$, $M=30.0Wm^{-2}$ of the AA model, and $b_1=33.0Wm^{-2}$, $b_2=1.02$ of the CRAE model. The calibrated AA and CRAE models were applied to the Kangjeongcheon watershed for model validation, and it was found out that both models can accurately produce the actual evaporation on annual and semiannual bases.

• Journal of KSNVE
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• v.8 no.1
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• pp.57-74
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• 1998

This paper is concerned with a combination of experimental and analytical investigation aimed at identifying modeling errors, accounted for the lack of correlation between experimental measurements and analytical predictions of the modal parameters for lap joint panels. A nonlinearity vibration test methodology, initiated from the theoretical analysis, is suggested for measurements of dynamic stiffnesses in a lap joint using the rivet fastener. Based on the experimental evidence on discrepancies between measured and predicted frequencies, improved finite element models of the joint are developed using PATRAN and ABAQUS, in which the beam element size is evaluated from the joint stiffnesses readily determined in the test. The beam element diameter as a principal design parameter is tuned to match experimental results within the evaluated bound value. Frequencies predicted by the proposed numerical model are compared with frequencies measured by the test. Improved predictions based on this new model are observed when compared with those based on conventional modeling practices.

• Journal of Korea Water Resources Association
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• v.33 no.1
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• pp.51-59
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• 2000

A dynamic model, which combined time series model with distributed-lag model, is applied to understand the relationship between rainfall and groundwater level. In the model, rainfall with distribution lags and past groundwater level as a dependent variables were used to estimate present groundwater level. The distribution of the lagged rainfall effects for groundwater levels was modeled by Almon polynomials. The model was applied to Banglim and Tanbu groundwater stations in Pyungchang river and Bocheong stream watershed which are representative basins for International Hydrological Program (IHP). The dynamic model represents observed groundwater levels very well and can be used to predict the levels. The model parameters reflect hydraulic characteristics of aquifer. In addition, from the parameters it appears that the increase in groundwater level due to rainfall takes place significantly within first two days of the rainfall event. The rainfall of the order of 18mm/day and 30mm/day at Banglim and Tanbu, respectively, had no significant effect on the groundwater levels.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.428-428
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• 2011

댐은 우리사회에 다양한 이익을 제공하는 반면 과거의 댐 붕괴 사례에 비추어 볼 때 붕괴로 인한 피해 규모는 막대하다. 세계 각국에서는 기존 댐들에 대한 잠재적 붕괴에 대비하기 위해 비상대처계획(Emergency Action Plan, EAP)과 같은 대책을 수립하여 붕괴로 인한 피해를 최소화하기 위한 노력을 기울이고 있다. 댐붕괴 모델링은 크게 댐 결괴부에 대한 예측과정과 댐 붕괴로 인한 하류부 홍수추적 과정으로 분류할 수 있다. 결괴부 예측과정은 댐붕괴로 인한 저수지 유출량에 가장 큰 영향을 미치는 부분이며 하류부 영향지역의 평가에도 매우 중요한 요소이다. 댐붕괴 예측모형은 결괴부에 대한 예측에 따라 매개변수 기반 모형과 물리기반 모형으로 분류된다. 매개변수 기반모형은 결괴형성과정을 단순 시간에 의한 함수로 고려하고 있으며 결괴부를 통한 흐름은 위어흐름으로 가정하고 있다. 이 모형은 현재 댐 붕괴 실무에서 가장 널리 이용되고 있으며 대표적인 모형은 FLDWAV/ DAMBRK 모형, HEC-RAS 모형 등이 있다. 물리기반 모형은 댐 붕괴진행 과정의 상세한 이해를 위해 시작되었으며 결괴부 흐름상황, 제체 침식, 제체가 불안정해지는 과정을 수리실험과 수리학, 토질역학, 구조역학 등의 이론을 통합하여 예측하는 기법으로 댐붕괴 과정을 좀 더 현실적으로 예측할 수 있으며 기존 붕괴된 댐들에 대한 붕괴 원인 및 진행과정을 규명할 수 있는 장점을 가진다. 최근 개발된 물리기반 댐 붕괴 모형은 HR-BREACH 모형, WINDAM 모형, FIREBIRD 모형 등이 있으며 지속적으로 연구되고 있다. 본 연구에서는 현재 진행 중에 있는 물리기반 댐 붕괴 모형들을 검토하고 현재 USDA, ARS에서 개발 중에 있는 WINDAM 모형을 이용하여 물리기반 모형의 수행에 요구되는 입력변수, 수행과정, 결과물에 대한 검토를 통해 댐 붕괴 관련 연구의 발전 방향을 모색하고 국내에서 물리기반 댐 붕괴 모형을 적용하기 위해 요구되는 사항과 한계점을 파악하여 댐 붕괴 실무로의 적용 방안을 마련하는 데 그 목적이 있다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6B
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• pp.551-560
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• 2010

This study presents the export of constituent transport loads through a river system. The proposed constituent transport load estimating procedure can be operated with the on-going Korean TMDL monitoring system. This study firstly discusses the use of a hydrologic simulation model (TANK) to estimate stream-flow for the 40 sub-catchments. Model parameters are estimated from 8-days intervals flow data which has been monitored by NIER since 2004. Constituent transport loads are estimated with the 7-parameter log linear model whose parameters are estimated by the minimum variance unbiased estimator. Results from Nakdong river basin reveals that the proposed procedure provides satisfactory TN, TP and SS transport load estimates. As an application, a representative load duration curve is derived to represent the overall hydrologic flux of TN, TP and SS at Nakdong river basin.

• Journal of Korea Water Resources Association
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• v.36 no.1
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• pp.23-32
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• 2003

This study aims at the derivation of representative IUH considering geomorphological factors. Nash model has been combined with geomorphological IUH to estimate the parameters of representative IUH. For this purpose, total 18 storm events which have been recorded upstream parts of Sangye control point in Bocheong river watershed, one of the tributary of Keum river basin, have been analysed. The results show that n value is 3.17 and K value is 7.01. And the results also show that IUHs driven by the method of moments vary with each storm events significantly. As a result of this study the IUH could be median distribution which is representative IUH among each storm events. It is believed that this result considered geomorphological factors is more superior and physically meaningful comparing with the existing methods.

• Water for future
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• v.27 no.2
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• pp.97-109
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• 1994

Parameters for the Synthetic Unit Hydrograph(SUH) using SCS and v methods(including modified type) are derived by regression analysis of the Representative Unit Hydrograph(RUH) of 22 basins in Korea. These derived SUHs were compared with the RUHs and those of Snyder and HYMO given by the Korea Institute of Construction Technology (KICT) for selected 4 basins. In SCS method, when correlated with the lag time of SUHs based on the whole basin rather than on the riverwise basins the peak discharge(excluding Bocheng stream) is close to that of RUH. BUt the peak time given by riverwise basins agrees closer to the RUH than by the whole basins. The modified Nakayasu type SUH(excluding Wi stream) associated with lag time based on riverwise basins gives better agreements to the RUH than that of Nakayasu method. And the modified Nakayasu type SUH gives much better agreement to the RUH than that of Nakayasu method for the case of both whole and riverwise basins.