• Journal of Korean Society of Forest Science
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• v.94 no.4 s.161
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• pp.243-251
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• 2005

This study was carried out to evaluate precipitation, geological and topographical factors from the landslide area occurred in Maeri, Sangdong-myeon, Gimhaesi, Gyeongsangnam-do. The landslide was affected by geo-topographical factors. Talus which is infiltrated easily by runoff was widely distributed in the landslide area. Concave areas on back- and toe-slope were built up colluvial materials and weathered soils. The colluvial materials were consisted of less weathered pebbles and stones (diameter: 10~100 cm) which are easily infiltrated during rainfall events. Also the landslide was mainly affected by an ascending of ground water table which is low in summit and high in toe-slope due to geo-topographical characteristics of the landslide area. The most important reason of the landslide was a lacking of drainage system of ground water despite the high infiltration rates of ground water in talus area during rainfall events.

• Journal of the Korean association of regional geographers
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• v.19 no.4
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• pp.615-626
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• 2013

In this study, spatial patterns of the urban flood vulnerability index in Seoul are examined by considering climate exposure, sensitivity, and adaptability associated with floodings for recent 5 year (2006~2010) period by the smallest administrative unit called Dong. According to the results of correlation analyses based on the IPCC(Intergovernmental Panel on Climate Change)'s vulnerability model, among many variables associated with urban flooding, rainwater tank capacity, 1-day maximum precipitation and flood pumping station capacity have statistically-significant, and relatively-high correlations with the number of flood damage in Seoul. The flood vulnerability map demonstrates that the extensive areas along Anyang and Joongnang streams show relatively high flood vulnerability in Seoul due to high sensitivity. Especially in case of Joongnang stream areas, climatic factors also contribute to the increase of flood vulnerability. At local scales, several Dong areas in Gangdong-gu and Songpa-gu also show high flood vulnerability due to low adaptability, while those in Gangnam-gu do due to high sensibility and climate factor such as extreme rainfall events. These results derived from the flood vulnerability map by Dong unit can be utilized as primary data in establishing the adaptation, management and proactive policies for flooding prevention within the urban areas in more detail.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.281-293
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• 2011

We investigated the causes and characteristics of a landslide at Hwangryeong Mountain, Busan, based on aerial photos, annual precipitation data, rock fracture patterns, and geomorphic features using GIS Software, and a statistical analysis of tilted trees. The analyzed slope shows evidence of a previous slope failure event and the possibility of future failures. Although the NW-SE trending slope was relatively stable until 1975, a large-scale slope failure occurred between 1975 and 1985 due to complex factors, including favorably oriented geologic structures, human activity, and heavy rain. This indicates that a detailed study of geologic structures, slope stability, and rainfall characteristics is important for slope cuttings that could be a major factor and cause of urban landsliding events. The statistic analysis of tilted trees shows a slow progressive creeping type of mass wasting with rock falls oblique to the dip of the slope, with the slope having moved towards the west since 1985. A concentration of tree tilting has developed on the northwestern part of the slope, which could reach critical levels in the future. The analysis of deformed trees is a useful tool for understanding landslides and for predicting and preventing future landslide events.

• Journal of Korea Water Resources Association
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• v.52 no.10
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• pp.753-761
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• 2019

Localized heavy storm is one of the major causes of flood damage in urban regions. According to the recent disaster statistics in South Korea, the frequency of urban flood is increasing more frequently, and the scale is also increasing. However, localized heavy storm is difficult to predict, making it difficult for local government officials to deal with floods. This study aims to construct a Flood risk matrix (FRM) using ensemble weather prediction data and to assess its applicability as a means of reducing damage by securing time for such urban flood response. The FRM is a two-dimensional matrix of potential impacts (X-axis) representing flood risk and likelihood (Y-axis) representing the occurrence probability of dangerous weather events. To this end, a regional FRM was constructed using historical flood damage records and probability precipitation data for basic municipality in Busan and Daegu. Applicability of the regional FRMs was assessed by applying the LENS data of the Korea Meteorological Administration on past heavy rain events. As a result, it was analyzed that the flood risk could be predicted up to 3 days ago, and it would be helpful to reduce the damage by securing the flood response time in practice.

• Journal of Korea Water Resources Association
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• v.52 no.6
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• pp.411-420
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• 2019

The objective of this study is to evaluate the appropriateness of methodology for designing urban sewer system using a rational method-based model, Makesw and an urban runoff model, SWMM. The Gunja basin was selected as a study area and precipitation, runoff, vegetation, soil, imperviousness data were used to estimate floods. The appropriateness of methodology was evaluated based on comparison analysis between floods estimated from Makesw and SWMM. The comparison analysis was conducted between floods estimated from Makesw and SWMM, which were simulated using design rainfall and measured rainfall from past inundation events. The comparison results showed that in the case of design rainfall, the rational method-based floods were larger than that based on SWMM in all main lines. However in several branch lines, the rational method-based floods were smaller than thoes based on SWMM. In addition, for the case of measured rainfall from past inundation events, it was easily to find the main and branch lines where the rational method-based floods were smaller than SWMM based ones. Especially, the lines where rational method-based floods were underestimated, were mostly main, $1^{st}$, $2^{nd}$ lines. It was concluded that the rational method-based results were not conservative. Based on rational method (steady flow analysis) and SWMM (unsteady flow analysis), the more conservative results the method provides, the more highly it is recommended to use in designing an urban sewer system.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.62-73
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• 2016

The variation of groundwater by wave, tide and precipitation conditions is closely related to the vegetation environment at the natural vegetation and sandy based beach, and it has a significant impact on the vegetation development and ground stabilization. In this study, the water temperature, electrical conductivity, and pressure were monitored at five observational stations normal to the Jinu-do(Island) shoreline of Nakdong river estuary from March 2012 to September 2014 (approximately 799 days) with the aim of measuring the variation in groundwater-table characteristics. The purpose of the study was to identify factors (tide, wave etc.) affecting groundwater-table variation using time series and correlation analysis, and to record spatial variations in the groundwater level and electrical conductivity as a result of storm events. The observational station in the intertidal zone was strongly affected by wave period and tide level. During the storm period, the groundwater-table and electrical conductivity were stabilized at the edge of sand dunes, vegetation, and areas of transition between freshwater and seawater.

• Journal of Korea Water Resources Association
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• v.50 no.1
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• pp.17-28
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• 2017

A recent increase in extreme weather events and flash floods associated with the enhanced climate variability results in an increase in climate-related disasters. For these reasons, various studies based on a high resolution weather radar system have been carried out. The weather radar can provide estimates of precipitation in real-time over a wide area, while ground-based rain gauges only provides a point estimate in space. Weather radar is thus capable of identifying changes in rainfall structure as it moves through an ungauged basin. However, the advantage of the weather radar rainfall estimates has been limited by a variety of sources of uncertainty in the radar reflectivity process, including systematic and random errors. In this study, we developed an ensemble radar rainfall estimation scheme using the multivariate copula method. The results presented in this study confirmed that the proposed ensemble technique can effectively reproduce the rainfall statistics such as mean, variance and skewness (more importantly the extremes) as well as the spatio-temporal structure of rainfall fields.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.6
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• pp.1219-1228
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• 2015

The Fixed Area ARFs (Area Reduction Factors) method has limitations in providing exact information about spatial distribution due to the lack of enough density of rain gauge stations. In this study the storm-centered ARF was evaluated between frontal and typhoon storm events utilizing radar precipitation. In estimating storm-centered ARFs, in order to consider the horizontal advection, direction, and spatial distribution of rain cells, the rotational angle of rainfall of each rainfall event and the optimum areal rainfall within the spatial rain cell envelope was taken into account. Compared with the frontal storm, the ARF of typhoon storm shows narrow range of variability. It is noted that the ARFs of frontal storm increases with the rainfall duration, but those of typhoon storm shows opposite pattern. As a result the typhoon ARFs appear greater than frontal ARFs for 1~3 hours of duration, but less for more than 6 hours of duration.

• Journal of Korea Water Resources Association
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• v.32 no.1
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• pp.15-29
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• 1999

A new methodology to analyze and quantify regional meteorological drought based on annual precipitation data has been introduced in this paper In this study, based on posterior probability estimator and Bayesian classifier in Spatial Analysis Neural Network (SANN), point drought probabilities categorized as extreme, severe, mild, and non drought events has been defined, and a Bayesian Drought Severity Index (BPSI) has been introduced to classify the region of interest into four drought severities. In addition, to estimate the regional drought severity for the entire region, regional extreme, severe, mild, and non drought probabilities which are the areal averages of point drought probabilities over the region has been computed and applied. In this study, the proposed methodology has been applied to analyze the regional drought of South Korea during 1967-1996 years. The drought severity for the whole South Korea was defined spatially at each year and each year was classified in a drought severity criterion. The results may be useful for water manager to understand the South Korean drought with respect to the spatial and temporal variation.

• Journal of Korea Water Resources Association
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• v.40 no.8
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• pp.629-641
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• 2007

This study estimated the urbanization effect of Seoul, the largest city in Korea, on its rainfall. For a comparative analysis, two different data sets are used: One is the precipitation data at the Jeonju rain gauge station, which has a relatively long record length but least urbanization effect, and the other at the Ichon rain gauge station, which has a short record length but located very near to Seoul with least urbanization effect. Also, the difference of the rainfall between Seoul and Jeonju rain gauge stations, as an indicator of urbanization effect, is quantified by use of the intervention model. As a result, it was found that the maximum rainfall intensity of the annual maximum rainfall events shows the increasing trend, its duration the decreasing trend, and the mean intensity the decreasing trend especially after 1960. Also, the quantification of urbanization effect using the intervention model shows that the increasing trend of rainfall intensity and total volume is still on going.