• Journal of the Korean Society of Safety
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• v.24 no.1
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• pp.89-94
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• 2009

The purpose of this study is to estimate the critical flood discharge and flash flood trigger rainfall for alarm system providing for a flash flood in mountainous area. The flash flood need non-linear approaching method, because rainfall-runoff is nonlinear and it is difficult to explain the existing linear rainfall-runoff. Hydrological characteristics would be utilized to apply such as hydrologic modelling or basin management. This study was effectively estimated a topographic characteristic factor of basin using the GIS. Especially, decided stream order using GIS at stream order decision that is important for input variable of GCIUH. A flash floods defined as a flood which follows shortly after a heavy or excessive rainfall event, with a few hours. In this study, we gave a definition that a critical flood for alarm is the flood when valley depth judging dangerous depth is over 0.5m depth from the bottom of channel. Result that calculate threshold discharge to use GCIUH, at the Mureung valley basin, flash flood trigger rainfall was 16.34mm in the first 20minutes when the threshold discharge was $14.54m^3/sec$.

• Journal of Korea Water Resources Association
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• v.51 no.9
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• pp.769-782
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• 2018

Estimation of design floods is typically required for hydrologic design purpose. Design floods are routinely estimated for water resources planning, safety and risk of the existing water-related structures. However, the hydrologic data, especially streamflow data for the design purposes in South Korea are still very limited, and additionally the length of streamflow data is relatively short compared to the rainfall data. Therefore, this study collected a large number design flood data and watershed characteristics (e.g. area, slope and altitude) from the national river database. We further explored to formulate a scaling approach for the estimation of design flood, which is a function of the watershed characteristics. Then, this study adopted a Hierarchical Bayesian model for evaluating both parameters and their uncertainties in the regionalization approach, which models the hydrologic response of ungauged basins using regression relationships between watershed structure and model. The proposed modeling framework was validated through ungauged watersheds. The proposed approach have better performance in terms of correlation coefficient than the existing approach which is solely based on area as a predictor. Moreover, the proposed approach can provide uncertainty associated with the model parameters to better characterize design floods at ungauged watersheds.

• Journal of Environmental Science International
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• v.14 no.11
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• pp.995-1004
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• 2005

As a research establish reservoir safety operation for small dam systems. This study presents hydrologic analysis conducted in the Duckdong and Bomun dam watershed based on various rainfall data and increase inflow. Especially the Duckdong dam without flood control feature are widely exposed to the risk of flooding, thus it is constructed emergency gate at present. In this study reservoir routing program was simulation for basin runoff estimating using HEC-HMS model, the model simulation the reservoir condition of emergency Sate with and without. At the reservoir analysis results is the Duckdong dam average storage decrease $20\%$ with emergency gate than without emergency gate. Also, the Bomun dam is not affected by the Duckdong flood control augmentation.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.168-176
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• 2010

This study proposes the improvement of the present Total Maximum Daily Load (TMDL) management system of MOE (Ministry of Environment). The margin of safety (MOS) is calculated by a method using standard error and a method using variability and uncertainty. The allocation of pollutant loads are calculated using three methods, equal load reduction method, equal percent removal method and method using equity standards. This study applied the improved TMDL management system to the Anyangcheon watershed. Since MOS varies from 12% to 44% due to the high variability of measured and simulated data, it must not be ignored in the TMDL. The method using equity standards is the most proper in this application since the others produced unrealistic allocations. Area, runoff, water use quantity, population and budget are considered for equity standards. This study shows that this allocation method can be also applicable for the administrative units as well as the sub-watersheds. Finally, Hydrologic Simulation Program-FORTRAN (HSPF) with the allocated pollutant load was used to confirm whether it satisfy the water quality standard or not. This study will be helpful to improve the MOS and allocation system TMDL in the future.

• Water Engineering Research
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• v.2 no.2
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• pp.123-138
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• 2001

An injection experiment was carried ut to investigate the pressure domain within which hydromechanical coupling influences considerably the hydrologic behavior of a granite rock mass. The resulting database is used for testing a numerical model dedicated to the analysis of such hydromechanical interactions. These measurements were performed in an open hole section, isolated from shallower zones by a packer set at a depth of 275 m and extending down to 840 m. They consisted in a series of flow meter injection tests, at increasing injection rates. Field results showed that conductive fractures from a dynamic and interdependent network, that individual fracture zones could not be adequately modeled as independent systems, that new fluid intakes zones appeared when pore pressure exceeded the minimum principal stress magnitude in that well, and that pore pressures much larger than this minimum stress could be further supported by the circulated fractures. These characteristics give rise to the question of the influence of the morphology of the natural fracture network in a rock mass under anisotropic stress conditions on the effects of hydromechanical couplings.

• Water Engineering Research
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• v.6 no.4
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• pp.179-187
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• 2005

This paper introduces the Cheonggye-cheon restoration project. The restoration project aims to revive the 600-year-old city of Seoul by recovering the historical heritage, guaranteeing safety from the deteriorated covering structures, creating the environment-friendly space, and revitalizing the neglected city centers. In order to understand the current hydrological cycle of the Chenggye-cheon watershed, the annual water balance of the region was calculated using the observed data including precipitation, runoff, water supply and sewage, and the changes in the groundwater level. The $2001{\sim}2002$ data were used to calibrate the WEP, and the $2003{\sim}2004$ data were used to verify the WEP. The calibration and validation results for the flood hydrograph how a reasonable value (at Majanggyo station, the R2 for the calibration period was 0.9, and that for the validation period was 0.7). According to the annual water balance of the Cheonggye-cheon watershed for 2004, the amount of surface runoff, infiltration, and evapotranspiration was 1,097mm, 216mm and 382mm, respectively, for an annual precipitation of 1,499mm. The application results from WEP, a distributed hydrological model, provide more detailed information of the watershed, and the model will be useful for improving the hydrological cycle in urban watershed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.6
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• pp.109-118
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• 2003

As a fundamental research to establish a safety operation plan for irrigation dams, this study presents hydrologic analysis conducted in Sungju Dam watershed based on various rainfall data. Especially those reservoirs without flood control feature are widely exposed to the risk of flooding, a safe and optimized operation program need to be improved against arbitrary flooding. In this study, reservoir routing program was developed and simulated for reservoir runoff estimation using WMS hydrology model. The model simulated the variations of reservoir elevation under the condition of open or closed emergency gate. In case of closed emergency gate, water surface elevation was given as 193.15 m, and this value exceeds the dam crest height by 1.65 m. When the emergency gate is open, the increment of water surface elevation is given as 192.01 m, and this value exceeds dam crest height by 0.57 m. As an alternative plan, dam height increase can be considered for flood control under the PMP (Probable Maximum Precipitation) condition. Since the dam size is relatively small compare to the watershed area, sound protection can be expected from the latter option rather than emergency gate installation.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.966-973
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• 2008

In recent, the collapses of cut-slope is gradually increased due to the heavy rains accompanied by typhoon. Specially, many cut-slope failures and landslides was happened to Goheung, Yeosu, Suncheon region, Jeonranamdo in the middle of September 2007. The slope of investigation is width 20 m, height 22 m, and the circular failure was occurred. The parent rocks of the slope are pyroclastic rock, namely andesite, andesitic tuff et al. and the weathering grade is completely weathered to residual soils owing to rapid weathering process and has the existence of fault zone and mafic dyke. Also, lots of extension cracks are presented and the hydrologic condition is very deteriorated. As a result of the limit equilibrium analysis, the safety factor is 1.09(in dry season) and 0.64(in wet season). For the stabilization of the cut-slope, we decided to use the retaining wall, anchors and drainage apparatus.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.245-254
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• 2001

The experimental study on disposal cover through the performance test facility offers reliability in the safety of near surface disposal of low and intermediate level radioactive waste. To ensure the long-term safety of the repository, the impermeability, integrity, resistance to degradation and ease of maintenance might be considered as the basic performance requirement of the disposal cover. considering the difficulties to meet these performance requirement by using single layer, the disposal cover design which is composed of top layer, middle drainage layer and bottom low permeability layer is schemed for the test facility. The water balance of the cover was evaluated by using HELP code. For the long-term monitoring of the soil moisture content and matric potential, TDR probes and tensiometers will be installed in 6 test cells. Each test cell is dimensioned 3$\times$3$\times$3.3m.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.231-238
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• 2017

Water supply safety index plays an important role on assessing the water supply capacity of hydrologic system. Due to the absence of consistent guidance, however, practical problems have been brought up on data period used for dam design and performance evaluation. Therefore, this study employed bivariate drought frequency analysis which is able to consider drought severity and duration simultaneously, in order to evaluate water supply capacity of multi-purpose dams. Drought characteristics were analyzed based on the probabilistic approach, and water supply capacity of five multi-purpose dams in Korea (Soyang River, Chungju, Andong, Daecheong, Seomjin River) were evaluated under the specific drought conditions. As a result, it would be possible to have stable water supply with their own inflow during summer and fall, whereas water shortage would occur even under the 1-year return period drought event during spring and winter due to low rainfall.