• Korean Journal of Ichthyology
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• v.31 no.1
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• pp.16-22
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• 2019

Investigations on the study of the distribution aspects and extinction threat evaluation of the Korean endemic species, Iksookimia pacifica were done from 2017 to 2018 in Korea. During the study period, the samples of I. pacifica were collected in 17 streams, 46 sites (from Baebongcheon Stream of Goseong-gun to Gunsuncheon Stream of Gangneung-si) among the noted 33 streams and 104 sampling sites investigated. The population size of I. pacifica was relatively large in streams such as Bukcheon, Baebongcheon, Hwasangcheon, Cheonjincheon, Ohhocheon Stream etc., but the population size was small in streams such as Sacheoncheon, Namcheon, Gangneung Namdaecheon Stream etc. The main habitat of I. pacifica was the downstream pool of clean water with slow velocity and sand bottoms, and their sensibility was estimated to be due to river work and water pollution. Comparing the previous records of the appearance of I. pacifica, they were first seen in Sampocheon Stream, but they did not appear in Jusucheon, Jeoncheon, Samcheok Osipcheon Stream. Given this evidence as noted for the 19.5% reduction in occupancy within 3 generations, in small appearance range ($1,343km^2$) and small occupancy area ($184km^2$), the number of locations were many (18) and the population was relatively large within the range of habitat. Therefore, I. pacifica is now considered a Near Threatened (NT) based on the IUCN Red List categories and criteria.

• Korean Journal of Plant Resources
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• v.32 no.2
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• pp.201-206
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• 2019

Alien invasive species are introduced with or without intent and spreading all over Korea. They are known to have negative effects on biodiversity such as economic and environmental damage and causing decrease or loss of native species. The habitats like wetland, reservoir and riverside are especially in danger of being invaded by alien species due to stress and disturbance. Therefore, Korea National Arboretum is steadily working on research and studies on managing alien invasive species. This research aims to collect basic information of Ludwigia peploides subsp. montevidensis (Spreng.) P.H. Raven which was found near riverside in Suwon-si and is concerned to become an invasive alien species. We expect the description, diagram and pictures of this taxon will be helpful for early detection and effective management.

• Journal of Cadastre & Land InformatiX
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• v.51 no.1
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• pp.97-110
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• 2021

This study estimated the delay factor, which is the ratio of travel time at the speed limit and travel time at the actual speed using real-time traffic information in Seoul. The actual travel speed on the road was lower than the maximum speed of the road and the travel speed was the slowest during the rush hour. As a result of accessibility analysis based on travel speed during the rush hour, the travel time at the actual speed was 37.49 minutes on average. However, the travel time at the speed limit was 15.70 minutes on average. This result indicated that the travel time at the actual speed is 2.4 times longer than that at the speed limit. In addition, this study proposedly defined the delay factor as the ratio of accessibility by the speed limit and accessibility to actual travel speed. As a result of delay factor analysis, the delay factor of Seoul was 2.44. The results by the administrative district showed that the delay factor in the north part areas of the Han River is higher than her south part areas. Analysis results after applying the relationship between road density and traffic volume showed that as the traffic volume with road density increased, the delay factor decreased. These results indicated that it could not be said that heavy traffic caused longer travel time. Therefore, follow-up research is needed based on more detailed information such as road system shape, road width, and signal system for finding the exact cause of increased travel time.

• Journal of Environmental Impact Assessment
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• v.30 no.3
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• pp.164-174
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• 2021

Information on biodiversity plays an important role in conservation planning for ecosystem. As existing biodiversity indices are calculated and predicted only based on the number of individuals and species, it is difficult to explain aspects of genetic and ecological diversity. Phylogenetic diversity can indirectly evaluate ecological diversity as well as genetic diversity overlooked by existing biodiversity assessments. In this study, typical metrics of biodiversity (e.g., species diversity, species richness, etc.) and phylogenetic diversity were evaluated together using a long-term monitoring data of winter birds in Jungrang, Cheonggye and Anyang stream where are designated as Seoul migratory bird reserves. Then discussed the meaning of each assessmentresult. In Jungrang and Anyang stream, the number of individuals generally decreased overtime, whereas in Cheonggye stream, there was no significant change. In addition, species abundance increased over time slightly in Cheonggye stream, while there was no significant change in Jungrang and Anyang stream. Species diversity temporally increased in Jungrang and Cheonggye stream, excluding Anyang stream, but phylogenetic diversity showed a tendency to increase only in Cheonggye stream. These changes in the biodiversity assessment indices are thought to be due to anthropogenic disturbances such as construction that occurred within each site, and it was shown that species diversity and phylogenetic diversity do not always lead to the same assessment results. Therefore, this study suggests that biodiversity assessment needs to be considered from various contexts such as genetic and ecological perspectives.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.5
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• pp.281-302
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• 2021

Railway projects have been consistently increasing in Korea. In relation to this trend, the mechanized tunneling using Tunnel Boring Machine (TBM) is preferably applied for mining urban areas and passing under rivers. The TBM tunneling under difficult grounds like mixed faces with high water pressure could require ground improvements for stable TBM advance or safe cutter head intervention (CHI). In this study, pre-grouting works for CHI in Daegok-Sosa railway project are presented in terms of the grouting zone design, the executions and the results, the lessons learned from the experience. It should be mentioned that the grouting from inside TBM was carried out several times and turned out to be inefficient in the project. Therefore, grouting experiences from the surface are highlighted in this study. Jet grouting was implemented on CHI points on land, while permeation grouting off shore in the Han River, which mostly allow to access the cutter head of TBM in free air with stable faces. The results of CHI works have been analyzed and the lesson learned are suggested.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.409-418
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• 2021

The land cover map is a very important data that is used as a basis for decision-making for land policy and environmental policy. The land cover map is mapped using remote sensing data, and the classification results may vary depending on the acquisition time of the data used even for the same area. In this study, to overcome the classification accuracy limit of single-period data, multi-series satellite images were used to learn the difference in the spectral reflectance characteristics of the land surface according to seasons on a U-Net model, one of the deep learning algorithms, to improve classification accuracy. In addition, the degree of improvement in classification accuracy is compared by comparing the accuracy of single-period data. Seoul, which consists of various land covers including 30% of green space and the Han River within the area, was set as the research target and quarterly Sentinel-2 satellite images for 2020 were aquired. The U-Net model was trained using the sub-class land cover map mapped by the Korean Ministry of Environment. As a result of learning and classifying the model into single-period, double-series, triple-series, and quadruple-series through the learned U-Net model, it showed an accuracy of 81%, 82% and 79%, which exceeds the standard for securing land cover classification accuracy of 75%, except for a single-period. Through this, it was confirmed that classification accuracy can be improved through multi-series classification.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.493-502
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• 2021

Recently, because of changes in temperature and rising water temperatures due to increased pollution sources, many algae have been produced in the water system. Therefore, there has been a lot of research using satellite images for the generation and monitoring of green algae. However, in prior studies, it is difficult to consider the optical properties of the local water system by using only a single index, and by using medium and low-resolution satellite images to conduct large-scale algae detection, there is a problem of accuracy in narrow, broad rivers. Therefore, in this work, we utilize high-resolution images of Sentinel-2 satellites to perform green algae detection on a single index (NDVI, SEI, FGAI) and development index (NDVI & SEI, FGAI & SEI) that mixes single indices. In this study, POD, FAR, and PC values were utilized to evaluate the accuracy of green algae detection algorithms, and the FGAI & SEI index showed the highest accuracy with 98.29% overall accuracy PC.

• Journal of Korea Water Resources Association
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• v.54 no.1
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• pp.27-38
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• 2021

Recently, many studies have been conducted to use the radar rainfall in hydrology. However, in the case of weather radar, the beam is blocked due to the limitation of the observation such as mountain effect, which causes underestimation of the radar rainfall. In this study, the radar rainfall was estimated using the Hybrid Sacn Reflectivity (HSR) technique for hydrological use of weather radar and the runoff analysis was performed using the GRM model which is a distributed rainfall-runoff model. As a result of performing the radar rainfall correction and runoff simulation for 5 rainfall events, the accuracy of the dual-polarization radar rainfall using the HSR technique (Q_H_KDP) was the highest with an error within 15% of the ground rainfall. In addition, the result of runoff simulation using Q_H_KDP also showed an accuracy of R2 of 0.9 or more, NRMSE of 1.5 or less and NSE of 0.5 or more. From this study, we examined the application of the dual-polarization radar and this results can be useful for studies related to the hydrological application of dual-polarization radar rainfall in the future.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.1
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• pp.53-68
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• 2021

The study aims to propose a locating method of green space for reducing Particulate Matter (PM) in ambient air in conjunction with its source traces and vulnerable groups. In order to carry out the aims and purposes, a literature review was conducted to derive indicators of vulnerable area to PM. Based on the developed indicators, the vulnerable areas and green spaces creation strategies for each cluster were developed for the case of Seongdong-gu, Seoul. As a result, six indicators for vulnerability analysis were came out including the vulnerable groups (children's facilities, old people's facilities), emission sources (air pollutant emission workplaces, roads), and environmental indicators (particulate matter concentration, NDVI). According to the six selected indicators, the target area was divided into 39 hexagons and analyzed to result the most vulnerable areas to particulate matter. As a result of comprehensive vulnerability analysis, the Seongsu-dong area was found to be the most vulnerable to particulate matter, and 5 clusters were derived through k-means cluster analysis. Cluster 1 was analyzed as areas that most vulnerable to particulate matter as a result of the comprehensive analysis, therefore urgent need to create green spaces to reduce particulate matter. Cluster 2 was areas that mostly belonged to the Han River. Cluster 3 corresponds to the largest number of hexagons, and since many vulnerable groups are distributed, it was analyzed as a cluster that required the creation of a green spaces to reduce particulate matter, focusing on facilities for vulnerable groups. Three hexagons are included in cluster 4, and the cluster has many roads and lacks vegetation in common. Cluster 5 has a lot of green spaces and is generally distributed with fewer vulnerable groups and emission sources; however, it has a high level of particulate matter concentration. In a situation where various green spaces creation projects for reducing particulate are being implemented, it is necessary to consider the vulnerable groups and emission sources and to present green space creation strategies for each space characteristic in order to increase the effectiveness of such projects. Therefore, this study is regarded as meaningful in suggesting a method for selecting a green area for reducing PM.

• Journal of Korea Water Resources Association
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• v.55 no.1
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• pp.71-84
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• 2022

The objective of this study is to develop a two-dimensional (2D) flood model that can perform accurate flood analysis with simple input data. The 2D flood inundation models currently used to create flood forecast maps require complex input data and grid generation tools. This sometimes requires a lot of time and effort for flood modeling, and there may be difficulties in constructing input data depending on the situation. In order to compensate for these shortcomings, in this study, a grid-based model that can derive accurate and rapid flood analysis by reflecting correct topography as simple input data was developed. The calculation efficiency was improved by extending the existing 2×2 sub-grid model to a 5×5. In order to examine the accuracy and applicability of the model, it was applied to the Gamcheon Basin where both urban and river flooding occurred due to Typhoon Rusa. For efficient flood analysis according to user's selection, flood wave propagation patterns, accuracy and execution time according to grid size and number of sub-grids were investigated. The developed model is expected to be highly useful for flood disaster mapping as it can present the results of flooding analysis for various situations, from the flood inundation map showing accurate flooding to the flood risk map showing only approximate flooding.