Seung-Jong Bae

Development of A Single Reservoir Agricultural Drought Evaluation Model for Paddy

This study aimed to develop an agricultural drought assessment methodology for irrigated paddy field districts from a single reservoir. Agricultural drought was defined as the reservoir storage shortage state that cannot satisfy water requirement from the paddy fields. The suggested model, SRADEMP (a Single Reservoir Agricultural Drought Evaluation Model for Paddy), was composed of 4 submodels: PWBM (Paddy Water Balance Model), RWBM (Reservoir Water Balance Model), FA (Frequency and probability Analysis model), and DCI (Drought Classification and Indexing model). Two indices, PDF (Paddy Drought Frequency) and PDI (Paddy Drought Index) were also introduced to classify agricultural drought severity Both values were divided into 4 steps, i.e. normal, moderate drought, severe drought, and extreme drought. Each step of PDI was ranged from +4.2 to -1.39, from -1.39 to -3.33, from -3.33 to -4.0 and less than -4.0, respectively. SRADEMP was applied to Jangheung reservoir irrigation district, and the results showed good relationships between simulated results and the observed data including historical drought records showing that SRADEMP explains better the drought conditions in irrigated paddy districts than PDSI.

Regional Drought Assessment Considering Climate Change and Relationship with Agricultural Water in Jeju Island

Recently, the occurrences of droughts have been increased because of global warming and climate change. Water resources that mostly rely on groundwater are particularly vulnerable to the impact of precipitation variation, one of the major elements of climate change, are very sensitive to changes in the seasonal distribution as well as the average annual change in the viewpoint of agricultural activity. In this study, the status of drought for the present and future on Jeju Island which entirely rely on groundwater using SPI and PDSI were analyzed considering regional distribution of crops in terms of land use and fluctuation of water demand. The results showed that the precipitation distribution in Jeju Island is changed in intensity as well as seasonal variation of extreme events and the amount increase of precipitation during the dry season in the spring and fall indicated that agricultural water demand and supply policies would be considered by regional characteristics, especially the western region with largest market garden crops. Regarding the simulated future drought, the drought would be mitigated in the SPI method because of considering total rainfall only excluding intensity variation, while more intensified in the PDSI because it considers the evapotranspiration as well as rainfall as time passed. Moreover, the drought in the northern and western regions is getting worse than in the southern region so that the establishment of regional customized policies for water supply in Jeju Island is needed.

Thresholds of Rainfall Duration and Intensity for Predicting Abrupt Landslide Occurrence

The objective of this study is to suggest rainfall threshold for landslide forecasting and warning. For this study, we chose the research area where landslide have occurred. And we performed infiltration-stability analysis with rainfall intensity-duration. As the results of this study, slope stability variation chart with rainfall intensity-duration are established. This kind of chart is believed to be able to be used for forecasting and warning the landslide caused by rainfall.

Development of Evaluation Indices for Redundant Farmlands Rehabilitation-Policy Directions

The objective of this study is to develop evaluation indices which can be applied to analyze rational rehabilitation-policy directions of redundant farmlands. To achieve this objective, the main tasks of this research are 1) categorizing the redundant farmlands rehabilitation types 2) developing the evaluation indices of redundant farmlands rehabilitation 3) determining the weights of each index. The redundant farmlands rehabilitation types were classified into agricultural rehabilitation type, non-agricultural rehabilitation type and hybrid type which are called by agricultural income model, rural environment improvement model and hybrid model as development project name, respectively. The 5 parts and 21 indices for evaluation of redundant farmlands rehabilitation directions were extracted by case studies and experts brainstorming. The weights of each index were determined by Analytic Hierarchy Process (AHP). The developed evaluation indices were applied to study areas located on Yanghwa district of Gongju-city and Aewol district of Jeju-city. From the results of this study, it was ascertained that the evaluation indices developed in this study would help the decision-makers in the planning process of redundant farmlands rehabilitation directions.

Assessment of Potential Flood Damage Considering Regional Flood Damage Cycle

Recently, flood has been increased due to climate change resulting in numerous damages for humans and properties. The main objective of this study was to suggest a methodology to estimate the flood vulnerability using Potential Flood Damage (PFD) concept. To evaluate the PFD at a spatial resolutions of city/county units, the 19 representative evaluation indexing factors were carefully selected for the three categories such as damage target (), damage potential () and prevention ability (). The three flood vulnerability indices of , and were applied for the 162 cities and counties in Korea for the pattern classification of potential flood damage. It is expected that the supposed PFD can be utilized as the useful flood vulnerability index for more rational and practical protection plans against flood damage.

Effects of the impervious cover change on runoff and pollutant loadings from a small watershed in South Korea

The main objective of this study was to evaluate the performance of the AGNPS (Agricultural Non-point Source Pollution) model in assessing the effects of impervious surface increase of rural area on hydrology and water quality. The Baran watershed, 385ha in size, was selected as the study site, which was a rural watershed experiencing fast increase in impervious surface area along with rapid urbanization. Digital maps extracted from the study site include a digital elevation map (DEM), slope distribution map, channel map, flow direction map, landuse map, soil map, and curve number map. Model parameters related to hydrology and water quality were calibrated and validated by comparing model predictions with the field data collected for 2 years (1999 through 2000). Calibration and validation resulted in R2 values of 0.67-0.91 for all the water quality parameters. The simulated runoff and water quality values also agreed well with the observed data. Some scenarios were used to simulate future impervious surface change by increasing impervious area or decreasing pervious area. Then each scenario was assessed in terms of its effects on hydrology and water quality. The method proposed in this study can be a useful tool for evaluating the effects of the impervious surface change on runoff and pollutant loadings for rural watersheds

Analysis of Landscape Structure on the Impervious Cover of the Gap-Stream Watershed using FRAGSTATS

An impervious cover in the watershed management has been used as effective indicators. It is a very useful barometer to measure the impacts of watershed development on aquatic systems. Hence, it is necessary to survey the impervious cover of a watershed and to develop an impervious cover model (ICM) for supporting best management practices. The main objectives of this study were to investigate the spatial patterns of the impervious cover, to calculate landscape indices using FRAGSTATS, and to develop an ICM in the Gap-stream watershed and its six sub-watersheds. The results showed that the impervious cover of the Gap-stream watershed increased from 4.9 % in 1975 to more than 11.2 % in 2000, the number of impervious cover fragments increased from 662 to 3,578, and the landscape shape index increased from 27.0796 to 91.1982. Fragmentation was severe within the Yudeungcheon downstream and the Gapcheon downstream of six sub-watersheds. This paper presented the results derived landscape indices to define landscape patterns and structure for the Gap-stream watershed. Our results indicate that altered land use might be influenced changes in landscape structure.

Analyzing the Spatial Centrality of Rural Villages for Green-Tourism using GIS and Social Network Analysis -Focusing on Rural Amenity and Human Resources-

The aim of this study is to analyze the green-tourism centrality considering spatial interaction using Gravity Model and social network method. The degree centrality and prestige centrality were applied as green-tourism centrality index. The rural amenity resources and human resources were counted as attraction factors, and a distance among villages was used as friction factor in gravity model. The weights of rural tourism amenity resources were calculated using the analytic hierarchy process(AHP) method and applied to evaluate green-tourism potentiality. The distance was measured with the shortest path among villages using geographic information system_(GIS) network analysis. The spatial interaction from gravity model were employed as link weights between nodal points; a pair villages. Using the spatial interaction, the degree-centrality and prestige-centrality indices were calculated by social network analysis and demonstrated possibility of developing integrated green-tourism region centered on high centrality villages.

Rural Amenity Survey and Evaluation

In the process industrialization and urbanization in Korea, rural area has been degraded with incurable problems including community aging and destruction of ancient cultural or natural rural amenities. However, the tangible and intangible resources in rural areas has highlighted in these days since the life quality elevated. Rural Amenity, the rural resources that give affection and agreeable feelings, is regarded as a solution that can revitalize the rural community. Therefore, Rural Development Administration (RDA) has been conducting nation-wide survey project for rural amenity resources to construct the databases of rural amenity distribution and richness. In this article, the survey project that was implemented from 2005 through 2009 was narrated in terms of methods and procedures. And, using surveyed data from the project, this study was implemented to evaluate rural amenity values based on Simple Additive Weighting (SAW) method considering living aspect and tourism aspect. For defining the set of evaluation criteria, rural amenity resources were classified into natural resources, cultural resources and social resources. The criteria’s weights were evaluated from the step wise pair-comparison results by Analytic Hierarchy Process (AHP) method. The two aspects evaluation method was applied to the selected 18 towns (called eup or myeon in Korea) in Chungcheongbuk-do. The results demonstrated the differences of amenity values as living conditions or tourism conditions.

A Spatio-temporal Change Analysis of Rural Landscape Patterns using Landscape Ecology Indices : Focused on a part of Gyeonggi-do

Studies in landscape ecology have emphasized on the relationship between landscape patterns and shapes. A variety of landscape metrics has been developed so far to quantify landscape structures. Therefore, their developments and widespread applications become possible with the advent of spatial information systems including geographic information systems(GIS) and remote sensing. This study is to grasp the change of land use and landscape ecology indices, and to analyze the change of landscape structure in a part of Gyeonggi-do during 15 years from 1985 to 2000. Green-area distribution maps and agricultural-area distribution maps for the analysis were reconstructed from land cover maps constructed by WAMIS(Water Management Information System). And then, 4 landscape ecology indices(TA, LPI, SHAPE_AM, CAI_MN) for the green-area and 5 landscape ecology indices(TA, PD, LPI, LSI, CAI_MN) for the agricultural-area were selected by using pearson correlation analysis. According to the spatio-temporal change analysis using landscape ecology indices, the green-area fragmentation of Yongin was the most severe of the study area and the agricultural-area fragmentation of Gwangju and Namyangju was more severe than any other regions.