Soojun Kim - Academia.edu (original) (raw)

Papers by Soojun Kim

Research paper thumbnail of Rainfall pattern analysis in 24 East Asian megacities using a complex network

Hydrology and Earth System Sciences

Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East... more Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East Asia via supply chain disruptions. Despite these significant economic impacts, understanding of the interconnection between rainfall patterns in the region is still currently limited. Here, we analyzed the spatial dependence of the rainfall patterns of 24 megacities in the region using complex analysis theory and discussed the technique's applicability. Each city and rainfall similarity were represented by a node and a link, respectively. Vital-node identification and clustering analysis were conducted using adjacency information entropy and multiresolution community detection. The results of vital-node identification analysis show that high-ranking nodes are cities that are located near main vapor providers in East Asia. Using multiresolution community detection, the groups were clustered to reflect the spatial characteristics of the climate. In addition, the climate links between each group were identified using cross-mutual information considering the delay time for each group. We found a strong bond between Northeast China and the southern Indochinese Peninsula and verified that the links between each group originated from the summer climate characteristics of East Asia. The results of the study show that complex network analysis could be a valuable method for analyzing the spatial relationships between climate factors.

Research paper thumbnail of Projection of Flight Cancellations and Economic Losses Caused by Future Climate Change

Journal of the Korean Society of Hazard Mitigation

The aviation industry plays an important role in daily life because of the increase of demand att... more The aviation industry plays an important role in daily life because of the increase of demand attributable to the development of air logistics as well as domestic and foreign tourism. However, the higher frequency of extreme weather caused by climate change has a large adverse effect on the operation of aircraft. As this effect is expected to increase, measures to reduce flight cancellation are needed. Therefore, in this study, the number of future flight cancellations and related economic losses were calculated for 1 3 domestic airports and six domestic airlines. To calculate the future climate of the airports, we used the recently released Shared Socioeconomic Pathways (SSP) climate change scenario. Then, we applied machine learning and the nearest neighbor with genetic algorithm method for spatial and temporal downscaling, respectively. The calculated results were applied to aircraft cancellation criteria and a damage estimation formula. Depending on the scenario, rainfall intens...

Research paper thumbnail of Development of the Method for Flood Water Level Forecasting and Flood Damage Warning Using an AI-based Model

Journal of the Korean Society of Hazard Mitigation

This study reviewed the applicability of AI-based models to predict flood water level and evaluat... more This study reviewed the applicability of AI-based models to predict flood water level and evaluate flood damage in small rivers with short arrival times. The Namyangju-si (Jingwan Bridge) watershed, where the most flood warnings have occurred, was selected as the target of study. Rainfall and water level data from 2008 to 2020 were collected for the watershed. A total of 40 rainfall events were identified when the water level was 1m or higher from June to September, corresponding to the flood season. Additionally, flood water level forecasting was performed using AI-based models such as deep neural network (DNN), long short term memory (LSTM), and storage function models. Predictive power evaluation revealed the DNN model displayed the lowest normalized root mean square error (NRMSE) with a value of 0.06. This study concludes that there are issues with the existing flood warning and heavy rain warning standards due to rainfall variability, correlation with the occurrence of damage c...

Research paper thumbnail of Uncertainty Analysis of Flood Damage Estimation Using Bootstrap Method and SIR Algorithm

Journal of Wetlands Research, 2011

We estimated the expected flood damage considering uncertainty which is involved in hydrologic pr... more We estimated the expected flood damage considering uncertainty which is involved in hydrologic processes and data. Actually, this uncertainty represents a freeboard or safety factor in the design of hydraulic structures. The uncertainty was analyzed using Bootstrap method, and SIR algorithm then the frequency based rainfalls were estimated for each method of uncertainty analysis. Also the benefits for each uncertainty analysis were estimated using 'multi-dimensional flood damage analysis(MD-FDA). As a result, the expected flood damage with SIR algorithm was 1.22 times of present status and Boostrap 0.92 times. However when we used SIR algorithm, the likelihood function should be selected with caution for the estimation of the expected flood damage.

Research paper thumbnail of Quantitative Flood Damage Evaluation Using Grid-Based Spatial Analysis Data

Journal of the Korean Society of Hazard Mitigation, 2021

In Korea, flood damage occurs every year due to typhoons and heavy rains, resulting in increasing... more In Korea, flood damage occurs every year due to typhoons and heavy rains, resulting in increasing damage to human lives and properties in urban areas. To reduce the scale of flood damage, economic analyses of flood-control work are conducted as part of efficient disaster management in the context of a limited budget. In this study, a quantitative evaluation of flood damage in Ulsan due to Typhoon Chaba was conducted using multi-dimensional flood damage analysis (MD-FDA). However, the land cover map applied to MD-FDA has limited data resolution and update intervals. Examination of domestic and foreign research cases to complement these spatial analysis data showed that grid data were being used in disaster-related fields. This study evaluated whether grid data are suitable for quantitative assessment through economic analyses conducted using new spatial analysis data such as road name address digital maps and 100 × 100 m grid-based spatial analysis data. The results of this study con...

Research paper thumbnail of Is the deep-learning technique a completely alternative for the hydrological model?: A case study on Hyeongsan River Basin, Korea

Stochastic Environmental Research and Risk Assessment, 2021

It is no doubt that the reliable runoff simulation for proper water resources management is essen... more It is no doubt that the reliable runoff simulation for proper water resources management is essential. In the past, the runoff was generally modeled from hydrologic models that analyze the rainfall-runoff relationship of the basin. However, since techniques have developed rapidly, it has been attempted to apply especially deep-learning technique for hydrological studies as an alternative to the hydrologic model. The objective of the study is to examine whether the deep-learning technique can completely replace the hydrologic model and show how to improve the performance of runoff simulation using deep-learning technique. The runoff in the Hyeongsan River basin, South Korea from 2013 to 2020 were simulated using two models, 1) Long Short-Term Memory model that is a deep learning technique widely used in the hydrological study and 2) TANK model, and then we compared the runoff modeling results from both models. The results suggested that it is hard to completely replace the hydrological model with the deep-learning technique due to its simulating behavior and discussed how to improve the reliability of runoff simulation results. Also, a method to improve the efficiency of runoff simulation through a hybrid model which is a combination of two approaches, deep-learning technique and hydrologic model was presented.

Research paper thumbnail of Anaylsis of rainfall relationships in East Asia using a complex network

Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East... more Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East Asia through supply chains. Despite the significant economic impacts, however, the understanding of the interconnection between rainfall patterns in the region is yet limited. Here, we analyzed spatial dependence in rainfall patterns of the 24 megacities in the region by means of complex analysis theory and discussed the technique's its applicability. Each city and correlation coefficient was represented by a node and a link, respectively. Vital node identification and clustering analysis were conducted using adjacency information entropy and multi-community detection. The groups were clustered to reflect the spatial characteristics of climate. In addition, the climate links between each group were identified through the cross-mutual information considering the delay time for each group. It was concluded that the complex network analysis can be a useful method for analyzing spatial relationship between climate factors.

Research paper thumbnail of Analysis of Applicability of Grid-based Spatial Analysis Data for Flood Risk Assessment

Journal of the Korean Society of Hazard Mitigation, 2020

The risk assessment techniques currently used in Korea have proven to have limitations as they pr... more The risk assessment techniques currently used in Korea have proven to have limitations as they provide flood risk assessments only. Although these assessment techniques comprehensively evaluate various factors such as wind and flood damage and social disruption, the administrative task-handling capacity is limited at the local government level. In this study, using electronic maps (which include building and road name addresses) and number of buildings in 31 cities and counties in Gyeonggi-do, only the statistical values located within the impact range of flood damage were extracted and evaluated for flood risk. The differences in statistical values resulting from data types were supplemented by the use of correction factors in the grid data. As a result of calculating the detailed index of each local government in Gyeonggi Province using the corrected grid data, the index was calculated in this order: Hwaseong, Yongin and Pyeongtaek. However, when the flood risk map and the number ...

Research paper thumbnail of Development of Decision Method for Investment Priority of River Flooding Disaster Risk Zone

Journal of the Korean Society of Hazard Mitigation, 2019

In disaster management, the importance of the prevention-preparedness phase has increased as comp... more In disaster management, the importance of the prevention-preparedness phase has increased as compared to the response-recovery stage in the past. In general, the state has allotted a large-scale budget for disaster prevention projects that needs to be invested efficiently in areas where it is required: that is, primarily in the order of high feasibility in flood risk zones. This study tries to suggest a decision method for investment priority of river flooding disaster prevention projects for risk zones. Evaluation factors such as the benefit-cost ratio (B/C), flood risk, residents' discomfort, past damage history, and alienated class are selected. Analytic Hierarchy Process (AHP) is applied to estimate the weight of each factor and sub-factor after the questionnaire survey. The applicability of the proposed method to the target area is evaluated.

Research paper thumbnail of A Bayesian Network-Based Integrated for Flood Risk Assessment (InFRA)

Sustainability, 2019

Floods are natural disasters that should be considered a top priority in disaster management, and... more Floods are natural disasters that should be considered a top priority in disaster management, and various methods have been developed to evaluate the risks. However, each method has different results and may confuse decision-makers in disaster management. In this study, a flood risk assessment method is proposed to integrate various methods to overcome these problems. Using factor analysis and principal component analysis (PCA), the leading indicators that affect flood damage were selected and weighted using three methods: the analytic hierarchy process (AHP), constant sum scale (CSS), and entropy. However, each method has flaws due to inconsistent weights. Therefore, a Bayesian network was used to present the integrated weights that reflect the characteristics of each method. Moreover, a relationship is proposed between the elements and the indicators based on the weights called the Integrated Index for Flood Risk Assessment (InFRA). InFRA and other assessment methods were compared...

Research paper thumbnail of A Study on Determination of Investment Priority of Flood Control Considering Flood Vulnerability

Journal of the Korean Society of Hazard Mitigation, 2018

The purpose of this study is to suggest a way to determine effectively investment priority for fl... more The purpose of this study is to suggest a way to determine effectively investment priority for flood control in a region. Potential flood damage(PFD) and flood risk indices were proposed from the national water resource plan. They have been used as the methods for assessing flood vulnerability. This study estimates the flood vulnerability index in each sub-basin after calculating weights on factors of the methods by using existing method, AHP(Analytic Hierarchy Process) and entropy theory. Based on the estimated index, investment priority of flood control in the basin was determined. The tendency of flood vulnerability and the expected effect of business was analyzed through the scenarios on applying flood mitigation projects. As a result, it was expected that the imbalance of the vulnerability was reduced in the watershed with the improvement of the vulnerability in the sub-basins which had the high flood vulnerability.

Research paper thumbnail of Study on Optimum Priority of Flood Control Projects Using the Maximized Economic Curve

Journal of the Korean Society of Hazard Mitigation, 2018

This study compares and considers various economic evaluation methods for flood control and deter... more This study compares and considers various economic evaluation methods for flood control and determines flood control priority. Economic evaluation is an essential factor to be considered in the establishment of flood control steps. It is also a way of reasonably analyzing the feasibility of a flood control project and the benefits for disaster prevention while determining the investment priorities of such projects. Therefore, it is necessary to project priority by selecting the economic evaluation method that meets the current condition and budget. For this purpose, this study constructed a database for twenty-eight cities and counties in Chungcheong province, using an improvement method. The characteristics were then examined and compared on the basis of three economic evaluations: Benefit/Cost (B/C), Net Present Value (NPV), Internal Rate of Return (IRR), and Weight Average Profit Index (WAPI). In addition, it was possible to arrive at a result that reflected each evaluation method well through the proposal of a Maximized Economy Curve (MEC), which accounts for both economic efficiency and the priority of flood control projects according to evaluation methods. The MEC is meaningful in that it presents the selection aspect of the economic evaluation method and the optimal business priority.

Research paper thumbnail of A Study on the Selection of Representative Indicators of Flood Vulnerability Assessment

Journal of the Korean Society of Hazard Mitigation, 2018

The purpose of this study is to select representative indicators that strongly influence flood vu... more The purpose of this study is to select representative indicators that strongly influence flood vulnerability in existing methods. Indicators for assessing the degree of vulnerability are widely scattered among previous studies, which creates challenges in adopting of flood vulnerability assessment measures. Therefore, it is necessary to remove duplicate indicators in such assessment measures and to select indicators with high impact. Therefore, the present study considers indicators in six existing evaluation methods such as FRI, PFD, FDRRI, FVA, FDI, and RSA. For this purpose, the representative indicators were selected by factor and principal component analysis (PCA) of Chungcheong-Do including Daejeon metropolitan and Sejong metropolis cities, and the explanatory power was verified by multiple regression analysis. An index consisting of representative indices was identified as the flood vulnerability indicator (R), and the characteristics were compared with the existing flood vulnerability index. R showed better results in metropolitan areas than indices of existing methods. This study can provide guidance when considering the representative indicators used in flood vulnerability assessment.

Research paper thumbnail of Decomposition of Water Level Time Series of a Tidal River into Tide, Wave and Rainfall-Runoff Components

Water, 2018

The water-level time series of a tidal river is influenced by various factors and has a complex s... more The water-level time series of a tidal river is influenced by various factors and has a complex structure, which limits its use as hydrological forecast data. This study proposes a methodology for decomposing the water-level time series of a tidal river into various components that influence the water level. To this end, the tide, wave, rainfall-induced runoff and noise components were selected as the main components that affect the water-level time series. The tide component and the wave component were first separated through wavelet analysis and curve fitting and then they were removed from the water-level data. A high-pass filter was then applied to the resulting time series to separate the rainfall-induced runoff component and the noise component. These methods made it possible to determine the rate of influence that each component has on the water level of a tidal river. The results could be used as a basis for calibrating a rainfall-runoff model and issuing flood forecasts and...

Research paper thumbnail of The Evaluation of Climate Change Impacts on the Water Scarcity of the Han River Basin in South Korea Using High Resolution RCM Data

Journal of Korea Water Resources Association, 2010

As an attempt to explore the impact of droughts which may be worse by the climate change, the cha... more As an attempt to explore the impact of droughts which may be worse by the climate change, the change in the water balance of the Han-river basin is analyzed. To accomplish it, we suggest a procedure consisting of three successive sub-procedures: daily rainfall generation for 70 years by the RegCM3 RCM (27 × 27 km) with the A2 scenario, daily discharge simulations by SLURP using the generated daily rainfall data, and monthly water balance analysis by K-WEAP (Korean Water Evaluation and Planning System) based on the SLURP simulation. Since significant uncertainty is involved in forecasting the future water consumption and water yields, we assumed three water consumption scenarios and fifty water yields scenarios. Three water consumption scenarios are, namely, "LOW", "MEDIUM", and "HIGH" according to the expected amount of water consumption. The fifty daily discharges are obtained from the SLURP simulations during the drought period. Finally, water balance analysis is performed by K-WEAP based on 150 combinations from three water consumption scenarios and the fifty daily discharges. Analysis of water scarcity in small basins of the Han River basin showed concentration of water scarcity in some small basins. It was also found that water scarcity would increase in all small basins of the Han River basin.

Research paper thumbnail of Assessment of Meteorological Drought in Korea under Climate Change

Advances in Meteorology, 2016

Drought has become one of the most important elements for water resources planning and management... more Drought has become one of the most important elements for water resources planning and management in Korea. The objective of this study is to estimate the spatial distribution of drought and change in the drought characteristics over time due to climate change. For the spatial characterization of drought, the standardized precipitation index (SPI) is calculated from the 45 observatories in Korea and the spatial distribution is also estimated based on the joint probability analysis using the copula method. To analyze the effect of climate change, spatial distribution of drought in the future is analyzed using the SPI time series calculated from Representative Concentration Pathways (RCPs) scenarios and HADGEM3-RA regional climate model. The results show that the Youngsan River and the northwest of Nakdong River basins in Korea have nearly doubled drought amount compared to the present and are most vulnerable to drought in near future (2016 to 2039 years).

Research paper thumbnail of Long-Term Simulation of Daily Streamflow Using Radar Rainfall and the SWAT Model: A Case Study of the Gamcheon Basin of the Nakdong River, Korea

Advances in Meteorology, 2016

In recent years, with the increasing need for improving the accuracy of hydrometeorological data,... more In recent years, with the increasing need for improving the accuracy of hydrometeorological data, interests in rain-radar are also increasing. Accordingly, with high spatiotemporal resolution of rain-radar rainfall data and increasing accumulated data, the application scope of rain-radar rainfall data into hydrological fields is expanding. To evaluate the hydrological applicability of rain-radar rainfall data depending on the characteristics of hydrological model, this study appliedRgaugeandRradarto a SWAT model in the Gamcheon stream basin of the Nakdong River and analyzed the effect of rainfall data on daily streamflow simulation. The daily rainfall data forRgauge,RZ, andRKDPwere utilized as input data for the SWAT model. As a result of the daily runoff simulation for analysis periods usingRZ(P)andRKDP(P), the simulation which utilizedRgaugereflected the rainfall-runoff characteristics better than the simulations which appliedRZ(P)orRKDP(P). However, in the rainy or wet season, th...

Research paper thumbnail of Hydrological Drought Analysis Based on Copula Theory

River Basin Management, 2016

Drought has been a more frequent phenomenon of major concern all over the world. From the perspec... more Drought has been a more frequent phenomenon of major concern all over the world. From the perspective of water resources management, one of the biggest problems associated with drought analyses is a lack of quantitative estimation for the target drought amount. The objective of this study is to examine the establishing process for the severity-duration-frequency (hereafter referred as "SDF") curves on climate change. The standardized truncation level that defines hydrological drought was estimated and a bivariate frequency analysis for drought duration and severity was derived. The SDF curves were also estimated. The methodology suggested in this study could be used as elementary data for water resources managements.

Research paper thumbnail of Wetland Construction: Flood Control and Water Balance Analysis

Environmental Engineering Research, 2010

Recent years have witnessed increasing interest in wetland constructions in Korea as a flood cont... more Recent years have witnessed increasing interest in wetland constructions in Korea as a flood control measure during the flood season and for consideration of the ecology during the non-flood season. In this study, hydraulic and hydrologic analyses were performed on a wetland construction plan for use as an alternative sustainable flood defense during the flood season, as well as a wetland that can protect the ecosystem during the non-flood season. The study area was the basin of the Topyeong-cheon stream, which is a tributary of the Nakdong River, including the Upo wetland, which is registered in the Ramsar Convention and the largest inland wetland in Korea. Wetlands were to be constructed at upstream and downstream of the Upo wetland by considering and analyzing seven scenarios for their constructions to investigate the effect of flood control during the flood season; it was found the best scenario reduced the flood level by 0.56 m. To evaluate the usefulness of the constructed wetlands during the non flood season, the water balance in the wetlands was analyzed, with the best scenario found to maintain a minimum water level of 1.3 m throughout the year. Therefore, the constructed wetlands could provide an alternative measure for flood prevention as well as an ecosystem for biodiversity.

Research paper thumbnail of Urban Drainage System Improvement for Climate Change Adaptation

Water, 2016

Recently, urban areas have experienced frequent, large-scale flooding, a situation that has been ... more Recently, urban areas have experienced frequent, large-scale flooding, a situation that has been aggravated by climate change. This study aims to improve the urban drainage system to facilitate climate change adaptation. A methodology and a series of mitigation strategies are presented to efficiently improve the urban drainage system in light of climate change. In addition, we assess the impact of climate change and predict the scale of potential future flood damage by applying the methodology and mitigation strategies to urban areas. Based on the methodology presented, urban flood prevention measures for Gyeyang-gu (Province), Incheon, Korea, was established. The validity of the proposed alternatives is verified by assessing the economic feasibility of the projects to reduce flood damage. We expect that the methodology presented will aid the decision-making process and assist in the development of reasonable strategies to improve the urban drainage system for adaptation to climate change.

Research paper thumbnail of Rainfall pattern analysis in 24 East Asian megacities using a complex network

Hydrology and Earth System Sciences

Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East... more Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East Asia via supply chain disruptions. Despite these significant economic impacts, understanding of the interconnection between rainfall patterns in the region is still currently limited. Here, we analyzed the spatial dependence of the rainfall patterns of 24 megacities in the region using complex analysis theory and discussed the technique's applicability. Each city and rainfall similarity were represented by a node and a link, respectively. Vital-node identification and clustering analysis were conducted using adjacency information entropy and multiresolution community detection. The results of vital-node identification analysis show that high-ranking nodes are cities that are located near main vapor providers in East Asia. Using multiresolution community detection, the groups were clustered to reflect the spatial characteristics of the climate. In addition, the climate links between each group were identified using cross-mutual information considering the delay time for each group. We found a strong bond between Northeast China and the southern Indochinese Peninsula and verified that the links between each group originated from the summer climate characteristics of East Asia. The results of the study show that complex network analysis could be a valuable method for analyzing the spatial relationships between climate factors.

Research paper thumbnail of Projection of Flight Cancellations and Economic Losses Caused by Future Climate Change

Journal of the Korean Society of Hazard Mitigation

The aviation industry plays an important role in daily life because of the increase of demand att... more The aviation industry plays an important role in daily life because of the increase of demand attributable to the development of air logistics as well as domestic and foreign tourism. However, the higher frequency of extreme weather caused by climate change has a large adverse effect on the operation of aircraft. As this effect is expected to increase, measures to reduce flight cancellation are needed. Therefore, in this study, the number of future flight cancellations and related economic losses were calculated for 1 3 domestic airports and six domestic airlines. To calculate the future climate of the airports, we used the recently released Shared Socioeconomic Pathways (SSP) climate change scenario. Then, we applied machine learning and the nearest neighbor with genetic algorithm method for spatial and temporal downscaling, respectively. The calculated results were applied to aircraft cancellation criteria and a damage estimation formula. Depending on the scenario, rainfall intens...

Research paper thumbnail of Development of the Method for Flood Water Level Forecasting and Flood Damage Warning Using an AI-based Model

Journal of the Korean Society of Hazard Mitigation

This study reviewed the applicability of AI-based models to predict flood water level and evaluat... more This study reviewed the applicability of AI-based models to predict flood water level and evaluate flood damage in small rivers with short arrival times. The Namyangju-si (Jingwan Bridge) watershed, where the most flood warnings have occurred, was selected as the target of study. Rainfall and water level data from 2008 to 2020 were collected for the watershed. A total of 40 rainfall events were identified when the water level was 1m or higher from June to September, corresponding to the flood season. Additionally, flood water level forecasting was performed using AI-based models such as deep neural network (DNN), long short term memory (LSTM), and storage function models. Predictive power evaluation revealed the DNN model displayed the lowest normalized root mean square error (NRMSE) with a value of 0.06. This study concludes that there are issues with the existing flood warning and heavy rain warning standards due to rainfall variability, correlation with the occurrence of damage c...

Research paper thumbnail of Uncertainty Analysis of Flood Damage Estimation Using Bootstrap Method and SIR Algorithm

Journal of Wetlands Research, 2011

We estimated the expected flood damage considering uncertainty which is involved in hydrologic pr... more We estimated the expected flood damage considering uncertainty which is involved in hydrologic processes and data. Actually, this uncertainty represents a freeboard or safety factor in the design of hydraulic structures. The uncertainty was analyzed using Bootstrap method, and SIR algorithm then the frequency based rainfalls were estimated for each method of uncertainty analysis. Also the benefits for each uncertainty analysis were estimated using 'multi-dimensional flood damage analysis(MD-FDA). As a result, the expected flood damage with SIR algorithm was 1.22 times of present status and Boostrap 0.92 times. However when we used SIR algorithm, the likelihood function should be selected with caution for the estimation of the expected flood damage.

Research paper thumbnail of Quantitative Flood Damage Evaluation Using Grid-Based Spatial Analysis Data

Journal of the Korean Society of Hazard Mitigation, 2021

In Korea, flood damage occurs every year due to typhoons and heavy rains, resulting in increasing... more In Korea, flood damage occurs every year due to typhoons and heavy rains, resulting in increasing damage to human lives and properties in urban areas. To reduce the scale of flood damage, economic analyses of flood-control work are conducted as part of efficient disaster management in the context of a limited budget. In this study, a quantitative evaluation of flood damage in Ulsan due to Typhoon Chaba was conducted using multi-dimensional flood damage analysis (MD-FDA). However, the land cover map applied to MD-FDA has limited data resolution and update intervals. Examination of domestic and foreign research cases to complement these spatial analysis data showed that grid data were being used in disaster-related fields. This study evaluated whether grid data are suitable for quantitative assessment through economic analyses conducted using new spatial analysis data such as road name address digital maps and 100 × 100 m grid-based spatial analysis data. The results of this study con...

Research paper thumbnail of Is the deep-learning technique a completely alternative for the hydrological model?: A case study on Hyeongsan River Basin, Korea

Stochastic Environmental Research and Risk Assessment, 2021

It is no doubt that the reliable runoff simulation for proper water resources management is essen... more It is no doubt that the reliable runoff simulation for proper water resources management is essential. In the past, the runoff was generally modeled from hydrologic models that analyze the rainfall-runoff relationship of the basin. However, since techniques have developed rapidly, it has been attempted to apply especially deep-learning technique for hydrological studies as an alternative to the hydrologic model. The objective of the study is to examine whether the deep-learning technique can completely replace the hydrologic model and show how to improve the performance of runoff simulation using deep-learning technique. The runoff in the Hyeongsan River basin, South Korea from 2013 to 2020 were simulated using two models, 1) Long Short-Term Memory model that is a deep learning technique widely used in the hydrological study and 2) TANK model, and then we compared the runoff modeling results from both models. The results suggested that it is hard to completely replace the hydrological model with the deep-learning technique due to its simulating behavior and discussed how to improve the reliability of runoff simulation results. Also, a method to improve the efficiency of runoff simulation through a hybrid model which is a combination of two approaches, deep-learning technique and hydrologic model was presented.

Research paper thumbnail of Anaylsis of rainfall relationships in East Asia using a complex network

Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East... more Concurrent floods in multiple locations pose systemic risks to the interconnected economy in East Asia through supply chains. Despite the significant economic impacts, however, the understanding of the interconnection between rainfall patterns in the region is yet limited. Here, we analyzed spatial dependence in rainfall patterns of the 24 megacities in the region by means of complex analysis theory and discussed the technique's its applicability. Each city and correlation coefficient was represented by a node and a link, respectively. Vital node identification and clustering analysis were conducted using adjacency information entropy and multi-community detection. The groups were clustered to reflect the spatial characteristics of climate. In addition, the climate links between each group were identified through the cross-mutual information considering the delay time for each group. It was concluded that the complex network analysis can be a useful method for analyzing spatial relationship between climate factors.

Research paper thumbnail of Analysis of Applicability of Grid-based Spatial Analysis Data for Flood Risk Assessment

Journal of the Korean Society of Hazard Mitigation, 2020

The risk assessment techniques currently used in Korea have proven to have limitations as they pr... more The risk assessment techniques currently used in Korea have proven to have limitations as they provide flood risk assessments only. Although these assessment techniques comprehensively evaluate various factors such as wind and flood damage and social disruption, the administrative task-handling capacity is limited at the local government level. In this study, using electronic maps (which include building and road name addresses) and number of buildings in 31 cities and counties in Gyeonggi-do, only the statistical values located within the impact range of flood damage were extracted and evaluated for flood risk. The differences in statistical values resulting from data types were supplemented by the use of correction factors in the grid data. As a result of calculating the detailed index of each local government in Gyeonggi Province using the corrected grid data, the index was calculated in this order: Hwaseong, Yongin and Pyeongtaek. However, when the flood risk map and the number ...

Research paper thumbnail of Development of Decision Method for Investment Priority of River Flooding Disaster Risk Zone

Journal of the Korean Society of Hazard Mitigation, 2019

In disaster management, the importance of the prevention-preparedness phase has increased as comp... more In disaster management, the importance of the prevention-preparedness phase has increased as compared to the response-recovery stage in the past. In general, the state has allotted a large-scale budget for disaster prevention projects that needs to be invested efficiently in areas where it is required: that is, primarily in the order of high feasibility in flood risk zones. This study tries to suggest a decision method for investment priority of river flooding disaster prevention projects for risk zones. Evaluation factors such as the benefit-cost ratio (B/C), flood risk, residents' discomfort, past damage history, and alienated class are selected. Analytic Hierarchy Process (AHP) is applied to estimate the weight of each factor and sub-factor after the questionnaire survey. The applicability of the proposed method to the target area is evaluated.

Research paper thumbnail of A Bayesian Network-Based Integrated for Flood Risk Assessment (InFRA)

Sustainability, 2019

Floods are natural disasters that should be considered a top priority in disaster management, and... more Floods are natural disasters that should be considered a top priority in disaster management, and various methods have been developed to evaluate the risks. However, each method has different results and may confuse decision-makers in disaster management. In this study, a flood risk assessment method is proposed to integrate various methods to overcome these problems. Using factor analysis and principal component analysis (PCA), the leading indicators that affect flood damage were selected and weighted using three methods: the analytic hierarchy process (AHP), constant sum scale (CSS), and entropy. However, each method has flaws due to inconsistent weights. Therefore, a Bayesian network was used to present the integrated weights that reflect the characteristics of each method. Moreover, a relationship is proposed between the elements and the indicators based on the weights called the Integrated Index for Flood Risk Assessment (InFRA). InFRA and other assessment methods were compared...

Research paper thumbnail of A Study on Determination of Investment Priority of Flood Control Considering Flood Vulnerability

Journal of the Korean Society of Hazard Mitigation, 2018

The purpose of this study is to suggest a way to determine effectively investment priority for fl... more The purpose of this study is to suggest a way to determine effectively investment priority for flood control in a region. Potential flood damage(PFD) and flood risk indices were proposed from the national water resource plan. They have been used as the methods for assessing flood vulnerability. This study estimates the flood vulnerability index in each sub-basin after calculating weights on factors of the methods by using existing method, AHP(Analytic Hierarchy Process) and entropy theory. Based on the estimated index, investment priority of flood control in the basin was determined. The tendency of flood vulnerability and the expected effect of business was analyzed through the scenarios on applying flood mitigation projects. As a result, it was expected that the imbalance of the vulnerability was reduced in the watershed with the improvement of the vulnerability in the sub-basins which had the high flood vulnerability.

Research paper thumbnail of Study on Optimum Priority of Flood Control Projects Using the Maximized Economic Curve

Journal of the Korean Society of Hazard Mitigation, 2018

This study compares and considers various economic evaluation methods for flood control and deter... more This study compares and considers various economic evaluation methods for flood control and determines flood control priority. Economic evaluation is an essential factor to be considered in the establishment of flood control steps. It is also a way of reasonably analyzing the feasibility of a flood control project and the benefits for disaster prevention while determining the investment priorities of such projects. Therefore, it is necessary to project priority by selecting the economic evaluation method that meets the current condition and budget. For this purpose, this study constructed a database for twenty-eight cities and counties in Chungcheong province, using an improvement method. The characteristics were then examined and compared on the basis of three economic evaluations: Benefit/Cost (B/C), Net Present Value (NPV), Internal Rate of Return (IRR), and Weight Average Profit Index (WAPI). In addition, it was possible to arrive at a result that reflected each evaluation method well through the proposal of a Maximized Economy Curve (MEC), which accounts for both economic efficiency and the priority of flood control projects according to evaluation methods. The MEC is meaningful in that it presents the selection aspect of the economic evaluation method and the optimal business priority.

Research paper thumbnail of A Study on the Selection of Representative Indicators of Flood Vulnerability Assessment

Journal of the Korean Society of Hazard Mitigation, 2018

The purpose of this study is to select representative indicators that strongly influence flood vu... more The purpose of this study is to select representative indicators that strongly influence flood vulnerability in existing methods. Indicators for assessing the degree of vulnerability are widely scattered among previous studies, which creates challenges in adopting of flood vulnerability assessment measures. Therefore, it is necessary to remove duplicate indicators in such assessment measures and to select indicators with high impact. Therefore, the present study considers indicators in six existing evaluation methods such as FRI, PFD, FDRRI, FVA, FDI, and RSA. For this purpose, the representative indicators were selected by factor and principal component analysis (PCA) of Chungcheong-Do including Daejeon metropolitan and Sejong metropolis cities, and the explanatory power was verified by multiple regression analysis. An index consisting of representative indices was identified as the flood vulnerability indicator (R), and the characteristics were compared with the existing flood vulnerability index. R showed better results in metropolitan areas than indices of existing methods. This study can provide guidance when considering the representative indicators used in flood vulnerability assessment.

Research paper thumbnail of Decomposition of Water Level Time Series of a Tidal River into Tide, Wave and Rainfall-Runoff Components

Water, 2018

The water-level time series of a tidal river is influenced by various factors and has a complex s... more The water-level time series of a tidal river is influenced by various factors and has a complex structure, which limits its use as hydrological forecast data. This study proposes a methodology for decomposing the water-level time series of a tidal river into various components that influence the water level. To this end, the tide, wave, rainfall-induced runoff and noise components were selected as the main components that affect the water-level time series. The tide component and the wave component were first separated through wavelet analysis and curve fitting and then they were removed from the water-level data. A high-pass filter was then applied to the resulting time series to separate the rainfall-induced runoff component and the noise component. These methods made it possible to determine the rate of influence that each component has on the water level of a tidal river. The results could be used as a basis for calibrating a rainfall-runoff model and issuing flood forecasts and...

Research paper thumbnail of The Evaluation of Climate Change Impacts on the Water Scarcity of the Han River Basin in South Korea Using High Resolution RCM Data

Journal of Korea Water Resources Association, 2010

As an attempt to explore the impact of droughts which may be worse by the climate change, the cha... more As an attempt to explore the impact of droughts which may be worse by the climate change, the change in the water balance of the Han-river basin is analyzed. To accomplish it, we suggest a procedure consisting of three successive sub-procedures: daily rainfall generation for 70 years by the RegCM3 RCM (27 × 27 km) with the A2 scenario, daily discharge simulations by SLURP using the generated daily rainfall data, and monthly water balance analysis by K-WEAP (Korean Water Evaluation and Planning System) based on the SLURP simulation. Since significant uncertainty is involved in forecasting the future water consumption and water yields, we assumed three water consumption scenarios and fifty water yields scenarios. Three water consumption scenarios are, namely, "LOW", "MEDIUM", and "HIGH" according to the expected amount of water consumption. The fifty daily discharges are obtained from the SLURP simulations during the drought period. Finally, water balance analysis is performed by K-WEAP based on 150 combinations from three water consumption scenarios and the fifty daily discharges. Analysis of water scarcity in small basins of the Han River basin showed concentration of water scarcity in some small basins. It was also found that water scarcity would increase in all small basins of the Han River basin.

Research paper thumbnail of Assessment of Meteorological Drought in Korea under Climate Change

Advances in Meteorology, 2016

Drought has become one of the most important elements for water resources planning and management... more Drought has become one of the most important elements for water resources planning and management in Korea. The objective of this study is to estimate the spatial distribution of drought and change in the drought characteristics over time due to climate change. For the spatial characterization of drought, the standardized precipitation index (SPI) is calculated from the 45 observatories in Korea and the spatial distribution is also estimated based on the joint probability analysis using the copula method. To analyze the effect of climate change, spatial distribution of drought in the future is analyzed using the SPI time series calculated from Representative Concentration Pathways (RCPs) scenarios and HADGEM3-RA regional climate model. The results show that the Youngsan River and the northwest of Nakdong River basins in Korea have nearly doubled drought amount compared to the present and are most vulnerable to drought in near future (2016 to 2039 years).

Research paper thumbnail of Long-Term Simulation of Daily Streamflow Using Radar Rainfall and the SWAT Model: A Case Study of the Gamcheon Basin of the Nakdong River, Korea

Advances in Meteorology, 2016

In recent years, with the increasing need for improving the accuracy of hydrometeorological data,... more In recent years, with the increasing need for improving the accuracy of hydrometeorological data, interests in rain-radar are also increasing. Accordingly, with high spatiotemporal resolution of rain-radar rainfall data and increasing accumulated data, the application scope of rain-radar rainfall data into hydrological fields is expanding. To evaluate the hydrological applicability of rain-radar rainfall data depending on the characteristics of hydrological model, this study appliedRgaugeandRradarto a SWAT model in the Gamcheon stream basin of the Nakdong River and analyzed the effect of rainfall data on daily streamflow simulation. The daily rainfall data forRgauge,RZ, andRKDPwere utilized as input data for the SWAT model. As a result of the daily runoff simulation for analysis periods usingRZ(P)andRKDP(P), the simulation which utilizedRgaugereflected the rainfall-runoff characteristics better than the simulations which appliedRZ(P)orRKDP(P). However, in the rainy or wet season, th...

Research paper thumbnail of Hydrological Drought Analysis Based on Copula Theory

River Basin Management, 2016

Drought has been a more frequent phenomenon of major concern all over the world. From the perspec... more Drought has been a more frequent phenomenon of major concern all over the world. From the perspective of water resources management, one of the biggest problems associated with drought analyses is a lack of quantitative estimation for the target drought amount. The objective of this study is to examine the establishing process for the severity-duration-frequency (hereafter referred as "SDF") curves on climate change. The standardized truncation level that defines hydrological drought was estimated and a bivariate frequency analysis for drought duration and severity was derived. The SDF curves were also estimated. The methodology suggested in this study could be used as elementary data for water resources managements.

Research paper thumbnail of Wetland Construction: Flood Control and Water Balance Analysis

Environmental Engineering Research, 2010

Recent years have witnessed increasing interest in wetland constructions in Korea as a flood cont... more Recent years have witnessed increasing interest in wetland constructions in Korea as a flood control measure during the flood season and for consideration of the ecology during the non-flood season. In this study, hydraulic and hydrologic analyses were performed on a wetland construction plan for use as an alternative sustainable flood defense during the flood season, as well as a wetland that can protect the ecosystem during the non-flood season. The study area was the basin of the Topyeong-cheon stream, which is a tributary of the Nakdong River, including the Upo wetland, which is registered in the Ramsar Convention and the largest inland wetland in Korea. Wetlands were to be constructed at upstream and downstream of the Upo wetland by considering and analyzing seven scenarios for their constructions to investigate the effect of flood control during the flood season; it was found the best scenario reduced the flood level by 0.56 m. To evaluate the usefulness of the constructed wetlands during the non flood season, the water balance in the wetlands was analyzed, with the best scenario found to maintain a minimum water level of 1.3 m throughout the year. Therefore, the constructed wetlands could provide an alternative measure for flood prevention as well as an ecosystem for biodiversity.

Research paper thumbnail of Urban Drainage System Improvement for Climate Change Adaptation

Water, 2016

Recently, urban areas have experienced frequent, large-scale flooding, a situation that has been ... more Recently, urban areas have experienced frequent, large-scale flooding, a situation that has been aggravated by climate change. This study aims to improve the urban drainage system to facilitate climate change adaptation. A methodology and a series of mitigation strategies are presented to efficiently improve the urban drainage system in light of climate change. In addition, we assess the impact of climate change and predict the scale of potential future flood damage by applying the methodology and mitigation strategies to urban areas. Based on the methodology presented, urban flood prevention measures for Gyeyang-gu (Province), Incheon, Korea, was established. The validity of the proposed alternatives is verified by assessing the economic feasibility of the projects to reduce flood damage. We expect that the methodology presented will aid the decision-making process and assist in the development of reasonable strategies to improve the urban drainage system for adaptation to climate change.