• KCID journal
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• v.19 no.1
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• pp.64-76
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• 2012

Recently, it has been increased disaster of crops and agricultural facilities with climate change such as regional storm, typhoon. However agricultural facilities have unsafe design criteria of improving drainage corresponding to this change. This study has analyzed the impact that inundation area and magnitude of drainage-facility is decided based on fixed- and unfixed-duration precipitation by applying revised design criteria of drainage for climate change. The result was shown that 1-day and 2-days rainfall for 20-years return period has increased about 11.4%, 4.4% respectively by changing fixed- to unfixed duration. And the increase rate of design flood was 15.0%. The result was also shown that Inundation area was enlarged by 6.6% as well as increased inundation duration under same basic condition in designed rainfall between fixed- and unfixed-duration. According to the analysis, it is necessary for pump capacity in unfixed-duration to be increased by 70% for same effect with fixed-duration. Therefore, when computing method of probability precipitation is changed from fixed one to unfixed-duration by applying revised design criteria, there seems to be improving effect in drainage design. Because 1440-minutes rainfall for 20-years return period with unfixed-duration is more effective than 1-day rainfall for 30-years return period with fixed-duration. By applying unfixed-duration rainfall, capacity of drainage facilities need to be expanded to achieve the same effects (Inundation depth & duration) with fixed-duration rainfall. Further study is required for considering each condition of climate, topography and drainage by applying revised design criteria.

• Journal of Korea Water Resources Association
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• v.51 no.1
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• pp.1-10
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• 2018

Recently, localized heavy rainfall has led to increasing flood damage in urban areas such as Gangnam, Seoul ('12), Busan ('13), Ulsan ('16) Incheon and Busan ('17) etc. Urban flooding occurs relatively rapidly compared to flood damage in river basin, and property damage including damage to houses, cars and shopping centers is more serious than facility damage to structures such as levees and small bridges. In Korea, heavy rain warnings are currently announced using the criteria set by KMA (Korea Meteorological Administration). However, these criteria do not reflect regional characteristics and are not suitable to urban flood. So in this study, estimated the flooding limit rainfall amount based on the damage records for Seoul and Ulsan. And for regions that can not estimate the flooding limit rainfall since there is no damage records, we estimated the flooding limit rainfall using a Neuro-Fuzzy model with runoff characteristics. Based on the estimated flooding limit rainfall, the urban flood warning criteria was set. and applied to the actual flood event. As a result of comparing the estimated flooding limit rainfall with the actual flooding limit rainfall, the error of 1.8~20.4% occurred. And evacuation time was analyzed from a minimum of 28 minutes to a maximum of 70 minutes. Therefore, it can be used as a warning criteria in the urban flood.

• Journal of Korea Water Resources Association
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• v.52 no.12
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• pp.963-973
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• 2019

This study reviews a urban flooding risk criteria estimation model to predict risk criteria in areas where flood risk criteria are not precalculated by using watershed characteristic data and limit rainfall based on damage history. The risk criteria estimation model was designed using Support Vector Machine, one of the machine learning algorithms. The learning data consisted of regional limit rainfall and watershed characteristic. The learning data were applied to the SVM algorithm after normalization. We calculated the mean absolute error and standard deviation using Leave-One-Out and K-fold cross-validation algorithms and evaluated the performance of the model. In Leave-One-Out, models with small standard deviation were selected as the optimal model, and models with less folds were selected in the K-fold. The average accuracy of the selected models by rainfall duration is over 80%, suggesting that SVM can be used to estimate flooding risk criteria.

• Journal of Korean Society of Disaster and Security
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• v.12 no.2
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• pp.15-24
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• 2019

In the previous study, the rainfall data of 1 hour, 6 hours and 3 days were used as the rainfall criterion according to the grade to trigger the debris flow in the highway area, using the rainfall data of Gangwon area and the rainfall time-series data at the spot where the debris flow occurred. In this study, we propose an early warning criterion of the highway debris flow triggering through appropriate combination of three rainfall criteria selected through previous studies and adjustments of rainfall criterion in the highway debris flow triggering. In addition, simulations were conducted using the time-series rainfall data of 2010~2012, which had a large amount of precipitation for the five sites where debris flows occurred in 2013. As a result of the study, the criteria for the early warning of highway unsteadiness on the highway were prepared. In case of the grade-based adjustment, it is preferable to apply the unified rating to the grade B. Also, if the fatigue of the monitoring is not a problem, adjusting it to A or S may be a way to positively cope with the occurrence of highway debris flow.

• Journal of the Korean Geotechnical Society
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• v.36 no.5
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• pp.5-16
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• 2020

The purpose of this study is to suggest the management criteria through the decision tree analysis for a seepage, which is an important instrumentation type of the fill dam. In the case of the seepage of the dam in Korea, seepage can be increased rapidly because rainfall directly flow into the downstream slope and abutment of dam during rainfalls. Therefore, it is necessary the management criteria for the seepage of the fill dam in consideration of rainfall. In this study, decision tree analysis was performed for a fill dam in Korea by setting the seepage as the response variable and the rainfall and water level of dam as explanatory variables. As the study results, the water level acted as an explanatory variable from the conditions under daily rainfall of 34.75 mm/day, and the branch conditions of the water level were analyzed to be 37.4 m and 35.23 m. 98% of the rainfall data is distributed under the conditions of the daily rainfall of 34.75 mm/day, and coverage of the seepage is indicated from 13.25 L/min to 24.24 L/min. When the rainfall and water level as the influence factors for the seepage were selected, the influence of the rainfall was dominant. Finally, the seepage of fill dam by considering the rainfall and water level was suggested as a management criteria.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.101-110
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• 2017

The National Emergency Management Agency (NEMA) presented the disaster prevention performance target rainfall (DPPTR) for disaster prevention. The estimation criteria for DPPTR is a 10 year cycle. On the other hand, the target rainfall recalculated every 10 years is difficult to reflect the current change in rainfall on climate change. In this study, the probability of precipitation using the recent rainfall data was prepared and the weights according to socio-economic criteria reflecting the urban characteristics and adjusted probability rainfall criteria were applied to the results. The difference between the existing target rainfall and recalculated result was compared. The input data for the estimated probability rainfall was selected from 6 points located in the rainfall observing station of Chungcheongnam-do, Daejeon region. As a result of the estimation, in the case of upward probability precipitation weight, some similar areas were observed. On the other hand, there were a few cases of upward or downward changes within 10 mm. Considering the rainfall variability and uncertainty due to climate change, the existing target rainfall does not present the condition properly. Therefore, hydrological designers need to calculate the target rainfall, reflecting the present condition.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.751-764
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• 2023

Gangwon State is centered on the Taebaek Mountains with very different climate characteristics depending on the region, and localized heavy rainfall is a frequent occurrence. Heavy rain disasters have a short duration and high spatial and temporal variability, causing many casualties and property damage. In the last 10 years (2012~2021), the number of heavy rain disasters in Gangwon State was 28, with an average cost of 45.6 billion won. To reduce heavy rain disasters, it is necessary to establish a disaster management plan at the local level. In particular, the current criteria for heavy rain warnings are uniform and do not consider local characteristics. Therefore, this study aims to propose a heavy rainfall warning criteria that considers the threshold rainfall for the advisory areas located in Gangwon State. As a result of analyzing the representative value of threshold rainfall by advisory area, the Mean value was similar to the criteria for issuing a heavy rain warning, and it was selected as the criteria for a heavy rain warning in this study. The rainfall events of Typhoon Mitag in 2019, Typhoons Maysak and Haishen in 2020, and Typhoon Khanun in 2023 were applied as rainfall events to review the criteria for heavy rainfall warnings, as a result of Hit Rate accuracy verification, this study reflects the actual warning well with 72% in Gangneung Plain and 98% in Wonju. The criteria for heavy rain warnings in this study are the same as the crisis warning stages (Attention, Caution, Alert, and Danger), which are considered to be possible for preemptive rain disaster response. The results of this study are expected to complement the uniform decision-making system for responding to heavy rain disasters in the future and can be used as a basis for heavy rain warnings that consider disaster risk by region.

• Journal of Korea Water Resources Association
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• v.45 no.3
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• pp.275-290
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• 2012

In this study, we have developed an optimal time distribution model through extraction of peaks over threshold (POT) series. The median values for annual maximum rainfall dataset, which are obtained from the magnetic recording (MMR) and the automatic weather system(AWS) data at Seoul meteorological observatory, were used as the POT criteria. We also suggested the improved methodology for the time distribution of extreme rainfall compared to Huff method, which is widely used for time distributions of design rainfall. The Huff method did not consider changing in the shape of time distribution for each rainfall durations and rainfall criteria as total amount of rainfall for each rainfall events. This study have suggested an extracting methodology for rainfall events in each quartile based on interquartile range (IQR) matrix and selection for the mode quartile storm to determine the ranking cosidering weighting factors on minutely observation data. Finally, the optimal time distribution model in each rainfall duration was derived considering both data size and characteristics of distribution using kernel density function in extracted dimensionless unit rainfall hyetograph.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.95-95
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• 2020

Urban flooding occurs in the form of internal-water inundation on roads and lowlands due to heavy rainfall. Unlike in the case of rivers, inundation in urban areas there is lacking in research on predicting and warning through measurement data. In order to analyze urban flood patterns and prevent damage, it is necessary to analyze flooding measurement data for various rainfalls. In this study, the pattern of urban flooding caused by rainfall was analyzed by utilizing the urban flooding measuring sensor, which is being test-run in the flood prone zone for urban flooding management. For analysis, 2019 rainfall data, surface water depth data, and water level data of a street inlet (storm water pipeline) were used. The analysis showed that the amount of rainfall that causes flooding in the target area was identified, and the timing of inundation varies depending on the rainfall pattern. The results of the analysis can be used as verification data for the urban inundation limit rainfall under development. In addition, by using rainfall intensity and rainfall patterns that affect the flooding, it can be used as data for establishing rainfall criteria of urban flooding and predicting that may occur in the future.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.957-965
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• 2008

Recently, slope stability analysis in current design criteria is criticized for its unrealistic assumption of groundwater table and slope stability analysis incorporating seepage analysis considering rainfall is gaining a recognition as an alternative. However, a reasonable method for determining the rainfall used in the seepage analysis has not yet been established. Rainfall input for seepage analysis is a time series of rainfall and is similar to the hyetograph which is usually obtained from hydrology. In this paper a method to obtain the hyetograph from the intensity-duration-frequency is proposed. The resulting hyetograph can be used in the in the slope design stage. Also some considerations for practical application of slope stability analysis considering the rainfall is included.