• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.164-164
• /
• 2023

This study investigates the importance of flood-influencing factors on the accuracy of flood risk mapping using the integration of remote sensing-based and machine learning techniques. Here, the Extreme Gradient Boosting (XGBoost) and Random Forest (RF) algorithms integrated with GIS-based techniques were considered to develop and generate flood risk maps. For the study area of NAPA County in the United States, rainfall data from the 12 stations, Sentinel-1 SAR, and Sentinel-2 optical images were applied to extract 13 flood-influencing factors including altitude, aspect, slope, topographic wetness index, normalized difference vegetation index, stream power index, sediment transport index, land use/land cover, terrain roughness index, distance from the river, soil, rainfall, and geology. These 13 raster maps were used as input data for the XGBoost and RF algorithms for modeling flood-prone areas using ArcGIS, Python, and R. As results, it indicates that XGBoost showed better performance than RF in modeling flood-prone areas with an ROC of 97.45%, Kappa of 93.65%, and accuracy score of 96.83% compared to RF's 82.21%, 70.54%, and 88%, respectively. In conclusion, XGBoost is more efficient than RF for flood risk mapping and can be potentially utilized for flood mitigation strategies. It should be noted that all flood influencing factors had a positive effect, but altitude, slope, and rainfall were the most influential features in modeling flood risk maps using XGBoost.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.12 no.3
• /
• pp.30-40
• /
• 1992

The area of grassland established and the arable land in forage production have been decreased recently in Korea. As a result, forages available from the grassland and the arable land provided only 40% of the total roughage consumed by cattle in 1991, compared with 54% in 1989. The decreasing trend of the forage production has been impinged on by a number of legislative. socio-economic. technical and other constraints negatively affecting grassland and forage development. Consequently. effective systems and strategies are quite necessary to have sustainable grassland farming in Korea. In spring and autumn, temperatures are too low for subtropical forage crops, and the summer monsoon climate is another serious limitation to the use of cool-season species. Therefore it is an imperative that not only the research-based grassland development but also the forage crop production should be strongly supported by the government authorities to overcome such climatic limitations. Private forest land holdings are of relatively small units in Korea. Accordingly. it is necessary and important to enlarge the forest land holdings per farm to develop as economic units of grassland. For this the government should introduce new policy measures such as for example: long-term leases of Sorest land and the idle arable land of absentee owners ; rational rental system of national and public forest lands; integrating livestock and forest production. All the laws and regulations standing in the way of the grassland development in forest lands should be modified and revised to open the way for much easier development of grassland. It is also proposed that a high level of financial incentives -hould be provided for structural improvements for the grassland development. They may be: mechanization facilitation, construction of new roads relating to grassland, and land exchange and consolidation. And it is basically necessary that financial enumeration or profits must be garanteed in order to motivate farmers to keep up farming continuously. For more efficient grassland development in mountainous areas, reorganization of Alpine Experiment Station and NAB1 Namwon Branch Station may be needed. Research should be strengthened for completion of pasture mixtures, development of maximum forage production methods with a view to saving labor and reducing production costs, introduction of grazing and forage conservation techniques. and utilization of rice straw as more palatable and nutritious forage source. In order to have more efficient and effective transfer of advanced forage production technologies to livestock farmers the user-clients. it is also essential that special training measures should be given to livestock farmers through making greater use of specialized research and extension workers.

• Journal of Wetlands Research
• /
• v.22 no.3
• /
• pp.200-216
• /
• 2020

Many studies conducted in Kenya regarding water resource governance have focused on the mandate of Water Resource Users Associations (WRUAs) with less attention being accorded to their effectiveness in conservation of wetlands. This study assessed the effectiveness of WRUA committees, and challenges faced in conservation of Rwamuthambi Sub-catchment. The study employed exploratory descriptive research design. Data was collected through questionnaires, semi-structured interviews, observations and review of secondary data. Chi square and descriptive statistics was used to analyze the data. The survey results revealed that only 15% of WRUA committee understood water resources management while 35% were aware of relevant legislations. Factors of wetland degradation showed significant association with existence of WRUA (χ2 (4, N=180) = 20.46, p< .01) where (χ2- chi square (degrees of freedom, N = sample size) = chi-square statistic value, p = p value), although WRUA contributions were perceived differently per agro-ecological zone (χ2 (8, N=147) = 15.51, p>.05). Challenges unearthed were inadequate financial and human resources, lack of understanding, ineffective collaborative governance, poor support from county government and private ownership of riparian land reserve. There is need for WRUAs to embrace collaborative governance for effective conservation of wetlands. Integration of sub catchment management plan with county land use plans and policy review is also required.

• Journal of Korean Society of Rural Planning
• /
• v.13 no.4
• /
• pp.9-22
• /
• 2007

With the establishment of municipalities, public interest in small towns in Korea has been on the rise. To initiate an effective study and suggest subsequent policies for small towns, it is necessary to analyze and discuss substantive issues based on specific conditions of these small towns. The primary objective of this paper is to categorize small towns into types and to analyze the peculiarities and differences of their internal factors. The focus of this research is to determine the general characteristics of the classified towns and to suggest specific revitalization and specialized studies about them. In the main analysis of this paper, 39 small towns are divided into sets according to urban rank, conditions of location, and size of the population in the central site. Furthermore, distinctions of the divided towns are analyzed using three constituents for urban organization, including populations, activities, and facilities/land. From the research results, it was determined that there is a difference between small town types, according to population, land cost, and urban activities, based upon the urban rank and size of the population in the central site. Therefore, this paper concludes it is necessary to conduct further studies on time series analysis regarding the peculiarity changes of the types, and to complement the variables for future related studies.

• Journal of Forest and Environmental Science
• /
• v.17 no.1
• /
• pp.88-103
• /
• 2001

It is one of the important tasks to accurately grasp features of the devastated land to revegetate the denuded, volcanic land. In the present report three factors of such features were discussed : the ash fall phenomenon the overflow of surface water, and the generation of sulfurous acid gas, which are all usual, harmful factors for the successful growth of introduced plants to such area. In addition, it is indicated that to overcome those harmful factors some artificial tools should be applied in such regions before the introduction of pioneer tree species such as Pinus thunbergii and etc. In our three-year pilot study it is found out that the use of mulching sheets developed originally by research members combined together with symbiotic microorganisms such as Pisolithus tinctorus Coker et Couch f. tinctorius was very effective. Experimental plots surveyed throughly in Mt. Fugendake in Nagasaki Prefecture and Mt. Sakurajima in Kagoshima Prefecture showed successful revegetation as models. Finally, for the revegetation of the denuded, volcanic land it is recommended that mulching sheets should be used together with symbiotic microorganisms.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.36 no.2
• /
• pp.24-31
• /
• 2008

Studies for demarcation of urban areas by ecological type have been developed, but the demarcation of urban areas by ecological perception is thus far dependent on artificial land use. Therefore, the purpose of this study is to find factors that account for the urban area ecosystems by surveying a variety of ecosystem factors. By land use type, the urban area of Gangdong District, Seoul was defined. Then ecological factors in each polygon were surveyed. Ecological factors are associated with energy use(building coverage ratio, floor area ratio and ground temperature), water circulation(biotope area factors and impermeable pave ratio) and biological diversity(bird appearance index and green area ratio). The correlation between each factor was analyzed. The results indicate that urban ground temperature is divided into three groups(high, middle and low) by the biotope area factor. The bird population is divided into two groups(abundant and scarce) by the green area ratio. Therefore, demarcating the urban areas by ecological type is applicable to the biotope area factor and green area ratio.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2002.11a
• /
• pp.167-172
• /
• 2002

This study examines and analyzes residential environment and factors with partial region of Chungjang-dong, Dong-gu, Gwangju based on land register and questionnaire. Consequently, most of residents are in their forties or over and working at downtown or place near it. It is found that rate of their own house is high and they live in the current house over 10 years. Residential factors at downtown area include its convenience, distance to workplace, convenient transportation and easy use of cultural and commercial facilities, but their consciousness of residence shows a low satisfaction with children education, air pollution, noise, parking facilities, green zone for making community, resting place, sunshine, view and privacy.

• Korean Journal of Remote Sensing
• /
• v.34 no.3
• /
• pp.553-564
• /
• 2018

Water use efficiency (WUE) is the amount of carbon uptake per unit of water use, which is a key measure of the functions of terrestrial ecosystems, as it is related to both the hydrologic and carbon cycles. Furthermore, it can vary with many factors, such as climate conditions and land cover characteristics, in different regions. In this study, we aim to understand the spatial and temporal variations in WUE on the Korean Peninsula as well as the associated response to drought. The Moderate Resolution Imaging Spectroradiometer (MODIS)-derived gross primary productivity (GPP) and evapotranspiration (ET) datasets and climate data were used to derive a drought index. Based on the monthly WUE, we found that WUE decreased during the monsoon summer in all regions and for all vegetation types. Furthermore, the annual WUE was negatively correlated with the drought index, with increasing correlation coefficients from the northern region to the southern region of the Korean Peninsula.

• Journal of Ecology and Environment
• /
• v.38 no.3
• /
• pp.343-352
• /
• 2015

The landscape setting of a habitat strongly influences the distribution, abundance, and species composition of waterfowl. Thus, habitat assessment is very important to understand the habitat characteristics that sustain waterfowl assemblages. In this study, we hypothesized that the excessive use of artificial materials when new wetlands are constructed negatively influences wintering waterfowl. To test this hypothesis, we measured environmental factors, assessed habitat, and investigated waterfowl at 13 artificial wetlands in the Nakdong River Basin. There were greater numbers of waterfowl species and individuals in artificial wetlands with high habitat assessment scores. In contrast, environmental factors did not affect waterfowl distribution. In particular, features of natural habitats, such as macrophytes and sandbars, and the surrounding land-use patterns were important factors for sustaining waterfowl assemblages in each created wetland. Our results show that promoting naturalness in wetlands and surrounding areas would increase the species diversity and abundance of waterfowl. Further, complex habitats, such as wetlands and some terrestrial habitats, support both aquatic and terrestrial species because mixed habitats feature a larger array of food sources than more limited habitats do.

• Wind and Structures
• /
• v.31 no.4
• /
• pp.321-334
• /
• 2020

Engineering type tropical cyclone (TC) wind field models are used to estimate TC wind hazard. Some of the models are well-calibrated using observation data, while others are not extensively compared and verified. They are all proxies to the real TC wind fields. The computational effort for their use differs. In the present study, a comparison of the predicted wind fields is presented by considering three commonly used models: the gradient wind field model, slab-resolving model, and a linear height-resolving model. These models essentially predict the horizontal wind speed at a different height. The gradient wind field model and linear height-resolving model are simple to use while the nonlinear slab-resolving model is more compute-intensive. A set of factors is estimated and recommended such that the estimated TC wind hazard by using these models becomes more consistent. The use of the models, including the developed set of factors, for estimating TC wind hazard over-water and over-land is presented by considering the historical tracks for a few sites. It is shown that the annual maximum TC wind speed can be adequately modelled by the generalized extreme value distribution.