• Korean Journal of Remote Sensing
• /
• v.38 no.5_3
• /
• pp.901-912
• /
• 2022

The frequency of disasters is increasing due to global climate change, and unusual heavy rains and rainy seasons are occurring in Korea. Periodic monitoring and rapid detection are important because these weather conditions can lead to drought and flooding, causing secondary damage. Although research using optical images is continuously being conducted to determine the waterbody, there is a limitation in that it is difficult to detect due to the influence of clouds in order to detect floods that accompany heavy rain. Therefore, there is a need for research using synthetic aperture radar (SAR) that can be observed regardless of day or night in all weather. In this study, using Sentinel-1 SAR images that can be collected in near-real time as open data, the UNet model among deep learning algorithms that have recently been used in various fields was applied. In previous studies, waterbody detection studies using SAR images and deep learning algorithms are being conducted, but only a small number of studies have been conducted in Korea. In this study, to determine the applicability of deep learning of SAR images, UNet and the existing algorithm thresholding method were compared, and five indices and Sentinel-2 normalized difference water index (NDWI) were evaluated. As a result of evaluating the accuracy with intersect of union (IoU), it was confirmed that UNet has high accuracy with 0.894 for UNet and 0.699 for threshold method. Through this study, the applicability of deep learning-based SAR images was confirmed, and if high-resolution SAR images and deep learning algorithms are applied, it is expected that periodic and accurate waterbody change detection will be possible in Korea.

• Journal of Korean Society of Disaster and Security
• /
• v.14 no.4
• /
• pp.9-15
• /
• 2021

The frequency of flash floods in mountainous areas is increasing due to the abnormal weather that occurs increasingly in the recent, and it causes human and material damages is increasing. Various plans for disaster mitigation have been established, but artificial plans such as raising embankment and dredging operation are inappropriate for valleys and rivers in national parks that prioritize nature protection. In this study, flood risk assessment was conducted for Gyeryongsan National Park in Korea using the WMS (Watershed Modeling System)which is rainfall runoff model for valleys and rivers in the catchment. As the result, it was simulated that it is flooding in three sub-catchments (Jusukgol, Sutonggol, Dinghaksa) of a total in Gyeryongsan National Park when rainfall over the 50 years return period occurs, and it was confirmed that the risk of trails and facilities what visitors are using was high. The risk of trails in national parks was quantitatively presented through the results of this study, and we intend to present the safe management guidelines of national parks in the future.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.5B
• /
• pp.497-507
• /
• 2010

Climate changes affect greatly natural ecosystem, human social and economic system acting on constituting the climate system such as air, ocean, life, glacier and land, etc. and estimating the current impact of climate change would be the most important thing to adapt to the climate changes. This study set the target area to Nakdong river watershed and investigated the impact of climate changes through analyzing precipitation tendency, and to understand the impact of climate changes on hydrological elements, analyzed elasticity of precipitation-streamflow. For the analysis of precipitation trend, collecting the precipitation data of the National Weather Service from major points of Nakdong river watershed, resampling them at the units of year, season and month, used as the data of precipitation trend analysis. To analyze precipitation-streamflow elasticity, collecting area average precipitation and long-term streamflow data provided by WAMIS, annual and seasonal time-series were analyzed. In addition, The results of this study and elasticity, and other abroad study compared with the elasticity analysis and the validity of this study was verified. Results of this study will be able to be utilized for study on a plan to increase of flood control ability of flooding constructs caused by the increase of streamflow around Nakdong river watershed due to climate changes and on a plan of adapting to water environment according to climate changes.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.38 no.4
• /
• pp.12-24
• /
• 2020

The purpose of this study is to analyze the influence of the water system on the location, spatial structure, and construction method of Hongju-eupseong, centering on Hongjumok-eupchi. During the Joseon Dynasty, the water system in Hongjumok-eupchi is composed of artificially constructed Seong-an Runnel and ponds based on a branch-shaped natural waterways flowing from south to north and west to east. Compiling the results of various literature records, excavations and analysis of map data, it can be seen that the water system has an important influence on the construction of Hongju-seong. Firstly, Hongju-seong from the Goryeo Dynasty to the late Joseon Dynasty is located using a circular shape of topographical structure and a small erosion basin formed on the inner side of the Hongseongcheon and Wolgyecheon streams without significant change in location. In particular, Wolgyecheon and Hongseongcheon are natural moats, which are harmonized with Sohyangcheon and riverside topographical structures, affecting the location and construction method of Hongju-seong, water related facilities, and the spatial structure of eupseong. It is understood that location characteristic of Hongju-seong reflects the urban location structure harmonized with waterways in ancient China and Korea. Secondly in harmony with the water system and topographic structure of Hongju-seong, it is an important factor in deciding the land use of the town, the arrangement of the town hall facilities and inducing various non-subsidiary measures such as the establishment of embankment forest with a secret function and the closure of the south gate. In addition, artificial drainage facilities such as Seongan runnel and ponds are being actively introduced from early on to protect the walls or towns from flooding of Wolgyecheon. Especially there were typical methods for protecting the walls from water damage such as the Joseon Dynasty stone castle structure that was integrated with saturn(soil wall) in the Goryeo Dynasty, retreating wall in the northern gate area in the late Joseon Dynasty, and the method of constructing wall using korean tile and stone floors between reinforced soil layers in the western and northern wall.

• Korean Journal of Microbiology
• /
• v.50 no.2
• /
• pp.137-151
• /
• 2014

Various studies have been conducted to investigate effects of dams on river ecosystems, but less information is available regarding damming impacts on downstream denitrification. We measured denitrification enzyme activity (potential denitrification rate) and denitrifier abundances (using nirS, nirK, and nosZ as markers) in dammed headstreams of the Nakdong River in South Korea. Sediments in Phragmites-dominated riparian areas and in-stream areas across streams (dammed vs. reference) with different streambed materials (gravel and sand) were sampled occasionally. We hypothesized that (i) the higher available N and C contents in sediments downstream of dams foster larger denitrifier communities than in the reference system and (ii) differences in potential denitrification rates across the systems correspond with denitrifier abundances. Despite 30 years of different hydrological management with dams and greater inorganic N and DOC contents in sediments downstream of dams, compared to the references, abundances of denitrifier communities and potential denitrification rates within the whole sediment were not significantly different across the systems. However, nirS and nosZ denitrifier abundances and potential denitrification rates were considerably increased in specific sediments downstream of dams (gravelly riparian and sandy in-stream) with regard to flooding events and seasonal temperature variation. nirK was not amplified in all sediments. Canonical correspondence analyses (CCA) revealed that the relationship between abundances of denitrifier communities and nutrient availabilities and potential denitrification rates was a weak one.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.1
• /
• pp.593-601
• /
• 2014

In this study, we investigated the methods of improving the capturing ability of acid fume by assessing the performance of slot-type external hood installed on both sides of an open surface tank for acid washing process. A field survey and the results of computational fluid dynamics revealed that capturing performance of existing hoods is very poor. To solve such problem, 'push-pull hood' that pushes from one side of an open surface tank and pulls on the other side was suggested. The initial prediction was that if a push-pull hood is used, the acid fume of an acid-washing tank surface could be moved towards the hood through the push flow. However, this study has confirmed that if the push flow velocity becomes too high, it could spread to other areas due to flooding from the hood. Therefore, if the push air supply is maintained at around 25 $m^3/min$(push 10 m/s), proper control flow is formed on the surface of a tank and acid fume that stayed at the upper part of the tank is smoothly captured toward the hood, significantly enhancing the capturing performance.

• Journal of Digital Convergence
• /
• v.15 no.11
• /
• pp.245-250
• /
• 2017

Flash floods is defined as the flooding of intense rainfall over a relatively small area that flows through river and valley rapidly in short time with no advance warning. So that it can cause damage property and casuality. This study is to establish the flash-flood warning system using 38 accident data, reported from the National Disaster Information Center and Land Surface Model(TOPLATS) between 2009 and 2012. Three variables were used in the Land Surface Model: precipitation, soil moisture, and surface runoff. The three variables of 6 hours preceding flash flood were reduced to 3 factors through factor analysis. Decision tree, random forest, Naive Bayes, Support Vector Machine, and logistic regression model are considered as big data methods. The prediction performance was evaluated by comparison of Accuracy, Kappa, TP Rate, FP Rate and F-Measure. The best method was suggested based on reproducibility evaluation at the each points of flash flood occurrence and predicted count versus actual count using 4 years data.

• Research in Plant Disease
• /
• v.9 no.2
• /
• pp.79-84
• /
• 2003

A wilt disease of commercial cyclamen (Cyclamen persicum) which grown in greenhouse was found in Gyeo-nggi province of Korea during the period from August, 2001 to July, 2002. The disease incidence was up to 42.7% in Kimpo, Gyeonggi province. The disease was more severe in ebb and flow irrigation system than con-ventional overhead flooding\'s. The wilted cyclamen plants showed the chlorosis of leaves and followed by the death. The vascular tissues of the infected basal stem and bulb were discolored with black streaks. The casual fungus was identified to be Fusarium oxysporum f. sp. cyclaminis on the basis of mycological characteristics. Effect of infected soil showed 100% infection rate when the cyclamen plants were grown in potting with infested soil. Examine resistant cultivar showed ‘Matis red’, ‘Schubert’, ‘Victoria’ and ‘Chopin’ were the resistant cultivars but most of cultivars were susceptible to Fusarium wilt. The control effect of chemicals for cyclamen wilt was not much efficient to curative effects even though. Benomyl WP and Fludioxonil SC on the Fusarium wilt had only preventive effects by soil drenching in the pot before inoculation of F. oxysporum. This is the first report on the fusarium wilt of cyclamen caused by F. oxysporum f. sp. cyclaminis in Korea.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.17 no.3
• /
• pp.104-115
• /
• 2014

A levee is defined as an man-made structure protecting the areas from temporary flooding. This paper suggests a methodology for establishing the levee GIS database using the airborne topographic LiDAR(Light Detection and Ranging) data taken in the Nakdong river basins and the WAMIS(WAter Management Information System) information. First, the National Levee Database(NLD) established by the USACE(United States Army Corps Engineers) and the levee information tables established by the WAMIS are compared and analyzed. For extracting the levee information from the LiDAR data, the DSM(Digital Surface Model) is generated from the LiDAR point clouds by using the interpolation method. Then, the slope map is generated by calculating the maximum rates of elevation difference between each pixel of the DSM and its neighboring pixels. The slope classification method is employed to extract the levee component polygons such as the levee crown polygons and the levee slope polygons from the slope map. Then, the levee information database is established by integrating the attributes extracted from the identified levee crown and slope polygons with the information provided by the WAMIS. Finally, this paper discusses the advantages and limitations of the levee GIS database established by only using the LiDAR data and suggests a future work for improving the quality of the database.

• Proceedings of the Korean Environmental Health Society Conference
• /
• 2005.06a
• /
• pp.263-272
• /
• 2005

Chlorine disinfection has been used in drinking water supply to disinfect the water-borne microbial disease which may cause to serious human disease. it is still the least costly, relatively easy to use, Chlorination is the primary means to disinfect portable water supplies and control bacterial growth in the distribution system. However, chlorine reacts with natural organic matter(NOM), that presents in nearly all water sources, and then produces disinfection by-products(DBPs), that have adverse health effects. Although the existent DBPs have been reported in drinking water supplies, it is not feasible to predict the levels of the various DBPs due to the complex chemistry reaction involved. 1. The objectives of this study is to investigate seasonal variation difference concentration of DBPs in the plant to tap water. The average concentration of THMs was 20.04 ${\mu}g/{\ell}$ , HAAs 8-15 ${\mu}g/{\ell}$ , HANs 2-4.5 ${\mu}g/{\ell}$ respectively. 2. Distant variation of DBPs furmation by the distance is that THMs concentration increased by 17% at 2km point from the plant and by 28% at 7km and HAAs, HANs also increase each by 16%, 32% at 2 km from the plant and 35%, 56% at 7 km. DBPs increase in water supply pipe continually, 3. The seasonal occurrence of BBPs is that in May and August DBPs concentration is very higher than in march, in May DBPs concentration is highest. The temperature is main factor of DBPs formation, precursor also. 4. Precursor which was accumulated for winter flowed into the raw water by flooding in spring and summer and produced DBPs. 5. Therefore for the supply of secure drinking water, it is required to protect precursor of flowing into raw water and to add to BCAA and DBAA to drinking water standards.