• Journal of Korea Water Resources Association
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• v.37 no.1
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• pp.43-54
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• 2004

The objective of this study is to propose reservoir operation method in relation to the suspended sediment concentration due to rainstorms. Present analysis is made for the Tamjin reservoir which is under construction. For the hydrologic computations the Huff rainfall distribution, Clark unit hydrograph method and Puls reservoir routing method are used. The variation of suspended sediment concentration is calculated by 2-dimensional RMA-4 model. As a result of this study, the possible intake time from the reservoir under low frequency flood is estimated and the rainfall-ret urn period - possible intake time relationship is established, which is very important in maintaining the water quality standard when supplying water from the reservoir for different utilizationurn period- possible intake time relationship is established, which is very important in maintaining the water quality standard when supplying water from the reservoir for different utilizations.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.26-30
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• 2011

최근 기후변화에 따라 강우의 패턴이 변화하고 있다. 강우일수는 줄어드는 반면, 강우강도는 증가하여, 홍수로 인한 많은 피해에 직면하고 있다. 이러한 기상이변은 홍수방어시스템을 위한 수공구조물에도 많은 영향을 미친다. 수공구조물을 설계할 때, 일반적으로 강우 기록들의 통계적 특성이 정상성을 가진다고 가정한다. 하지만 최근의 강우 자료를 분석하면, 시간에 따라 평균, 분산, 왜곡도와 같은 기본 통계량이 변화하는 것을 알 수 있다. 따라서, 수공구조물의 설계를 위한 확률 강우량은 이러한 기후변화에 따른 자료의 특성을 반영할 필요가 있다. 본 연구의 목적은 강우 자료의 비정상성의 특성을 이용하여 확률강우량을 산정하는 것이다. 최근 비정상성 강우빈도해석에 대한 연구가 활발히 진행되고 있는데, 이들 연구는 대부분 목표연도까지 경향성의 기울기가 증가, 또는 일정하다고 가정한다. 하지만, 현재는 경향성이 있지만, 목표연도에는 경향성이 없을 경우도 있고, 또는 경향성이 있어도 그 기울기가 적어지는 경향을 보일 수도 있다. 본 연구에서는 현시점과 목표연도의 시점에 대한 경향성 기울기의 변화를 고려하여 비정상성 강우빈도해석을 수행하였다. 대상지점 선정은 통계적 경향성 검정, Mann-Kendall test를 이용하여 1994년(현재시점)에 경향성이 있다고 판단되는 관측지점을 대상지점으로 선정하였다. 분석 방법은 24시간 임계지속시간의 연최대강우자료를 구축하였다. 자료를 현시점까지 선형회귀식을 이용하여 잔차 계열을 산정하고, Gumbel 분포를 이용하여 확률 잔차를 산정하였다. 확률강우량을 추정하기 위해 추세요소를 산정하였다. 기울기의 증가 혹은 감소 경향을 회귀모형을 이용하여 추세요소를 산정하였고, 잔차의 확률빈도와 추세요소의 합으로 비정상상 확률강우량을 산정하였다.

• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.241-252
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• 2015

Runoff behaviors by five bias correction methods were analyzed, which were Change Factor methods using past observed and estimated data by the estimation scenario with average annual calibration factor (CF_Y) or with average monthly calibration factor (CF_M), Quantile Mapping methods using past observed and estimated data considering cumulative distribution function for entire estimated data period (QM_E) or for dry and rainy season (QM_P), and Integrated method of CF_M+QM_E(CQ). The peak flow by CF_M and QM_P were twice as large as the measured peak flow, it was concluded that QM_P method has large uncertainty in monthly runoff estimation since the maximum precipitation by QM_P provided much difference to the other methods. The CQ method provided the precipitation amount, distribution, and frequency of the smallest differences to the observed data, compared to the other four methods. And the CQ method provided the rainfall-runoff behavior corresponding to the carbon dioxide emission scenario of SRES A1B. Climate change scenario with bias correction still contained uncertainty in accurate climate data generation. Therefore it is required to consider the trend of observed precipitation and the characteristics of bias correction methods so that the generated precipitation can be used properly in water resource management plan establishment.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.219-229
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• 2011

In this study, Correlation analysis for relationship between storm characteristics and flood damage cost was carried out using histogram analysis. The spatial range of flood damage cost data was the whole country and 16 provinces in the Korea, and period range was 16 years, from 1994 to 2009. According to the results of this analysis, most of total flood damage cost was highest in small; middle scale rainfall events of high frequency. Based on the results of comparison among 16 provinces, the ability to prevent flood demage of metropolitan was better than that of provinces. And the storm characteristics of causing maximum flood damage cost was different from each provinces. Therefore, the construction size in flood defence measures has to be determined when flood defence measures considering the results of this study as an useful guideline.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.259-259
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• 2016

This study examined Artificial Neurons Networks model (ANNs) for forecast flash discharge at Southern part of Thailand by using rainfall data and discharge data. The Sungai Kolok River Basin has meant the border crossing between Thailand and Malaysia which watershed drains an area lies in Thailand 691.88 square kilometer from over all 2,175 square kilometer. The river originates in mountainous area of Waeng district then flow through Gulf of Thailand at Narathiwat Province, which the river length is approximately 103 kilometers. Almost every year, flooding seems to have increased in frequency and magnitude which is highly non-linear and complicated phenomena. The purpose of this study is to forecast runoff on Sungai Kolok at X.119A gauge station (Sungai Kolok district, Narathiwat province) for 3 days in advance by using Artificial Neural Networks model (ANNs). 3 daily rainfall stations and 2 daily runoff station have been measured by Royal Irrigation Department and Meteorological Department during flood period 2000-2014 were used as input data. In order to check an accuracy of forecasting, forecasted runoff were compared with observed data by pursuing Coefficient of determination ($R^2$). The result of the first day gets the highest accuracy and then decreased in day 2 and day 3, consequently. $R^2$values for first day, second day and third day of runoff forecasting is 0.71, 0.62 and 0.49 respectively. The results confirmed that the ANNs model can be used when the range of collected dataset is short and real-time operated. In conclusion, the ANNs model is suitable to runoff forecasting during flood incident of Sungai Kolok river because it is straightforward model and require with only a few parameters for simulation.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.963-978
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• 2020

Earthquakes can induce a large number of landslides and cause very serious property damage and human casualties. There are two issues in study on earthquake-induced landslides: (1) slope stability analysis under seismic loading and (2) debris flow run-out analysis. This study aims to review technical studies related to the development and application of earthquake-induced landslide models (seismic slope stability analysis). Moreover, a pilot application of a physics-based slope stability model to Mt. Umyeon, in Seoul, with several earthquake scenarios was conducted to test regional scale seismic landslide mapping. The earthquake-induced landslide simulation model can be categorized into 1) Pseudo-static model, 2) Newmark's dynamic displacement model and 3) stress-strain model. The Pseudo-static model is preferred for producing seismic landslide hazard maps because it is impossible to verify the dynamic model-based simulation results due to lack of earthquake-induced landslide inventory in Korea. Earthquake scenario-based simulation results show that given dry conditions, unstable slopes begin to occur in parts of upper areas due to the 50-year earthquake magnitude; most of the study area becomes unstable when the earthquake frequency is 200 years. On the other hand, when the soil is in a wet state due to heavy rainfall, many areas are unstable even if no earthquake occurs, and when rainfall and 50-year earthquakes occur simultaneously, most areas appear unstable, as in simulation results based on 100-year earthquakes in dry condition.

• Journal of Korea Water Resources Association
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• v.34 no.1
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• pp.81-90
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• 2001

A dynamic flood frequency analysis model was proposed for the frequency analysis in ungaged catchment and applied to 6 subbasins in Pyungchang River basin. As the dynamic flood frequency model requires precipitation, rainfall loss system, and runoff analysis, we adopt the rectangular pulse model, the SCS formula, and the geomorphoclimatic IUH(GcIUH) for the application. Input data for the analysis was borrowed from the results of the statistical flood frequency analysis using L-moment method for the same catchment, and then the return period was estimated using the model. This result was also compared with the return period estimated from the statistical analysis. By comparing with the results from two cases, we found the dynamic flood frequency analysis gave higher estimates than those from statistical analysis for the whole subbasins. However, the dynamic flood frequency analysis model has a potential to be used for determining the design flood for small hydraulic structure in ungaged catchment because it uses only physical parameters for flood frequency analysis. And this model can be easily applicable to other watersheds as the scale effect is negligible.

• Journal of the Korean GEO-environmental Society
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• v.16 no.1
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• pp.29-36
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• 2015

Current domestic research is to demonstrate the effectiveness and efficiencies of flood prevention measures through one-dimensional numerical analysis and this study's object is to help water managers to make the efficient decisions by applying the two-dimensional urban run off model XP-SWMM model in the flooded area and comparing with the flood prevention measures. Statistics were analyzed, based on the data collected from Cheongju Weather Service from 1967 to 2011 for 45 years. 50 years Flood frequency simulations of water flow capacity analysis of the target area for flooded areas $539,548m^2$, inundation depth 1.0 m, was analyzed by inundation time of 48 minutes. When comparing with the constructions of bypass road and underground storage facilities to increase the water flow capacity of A1 small drainage areas as flood protection, if you install a batching target underground detention basin with a capacity of $13,500m^3$, it is expected that the flood by rainfall with frequency of 50 years will be resolved completely. In preparation for extreme weather in the future flood mitigation measures, underground storage tank installation is considered a better efficient way.

• 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.

• Journal of Korea Water Resources Association
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• v.52 no.3
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• pp.173-185
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• 2019

The Korean Peninsula is considered as one of the most typhoon related disaster prone areas. In particular, the potential risk of flooding in coastal areas would be greater when storm surge and heavy rainfall occurred at the same time. In this context, understanding the mechanism of the interactions between them and estimating the risk associated with the concurrent occurrence are of particular interests especially in low-lying coastal areas. In this study, we developed a Poisson-Generalized Pareto (Poisson-GP) distribution based storm surge frequency analysis model to combine the occurrence of the exceedance of a threshold, that is the peaks over threshold (POT), within a Bayesian framework. The storm surge frequency analysis technique developed through this study might contribute to the improvement of disaster prevention technology related to storm surge in the coastal area.