• Explosives and Blasting
• /
• v.21 no.3
• /
• pp.23-35
• /
• 2003

An analytical diffusion model for flood routing with backwater effects and lateral flows is developed. The basic diffusion equation is linearized about an average depth of (H + h), and is solved using the boundary conditons which take into account the effects of backwater and lateral flows. Scouring phenomenon around pier which affects on the support function of pier and the stabilization if river bed is a complex problem depending on flow properties and river bed state as well as pier geometry. therefore, there is no uniting theory at present which would enable the designer to estimate, with confidence, the depth of scour at bridge piers. The various methods used in erosion control are collectively called upstream engineering, HEC-RAS Model, underwater blasting. They consist of reforestation, check-dam construction, planting of burned-over areas, contour plowing and regulation of crop and grazing practices. Also included are measures for proper treatment of high embankments and cuts and stabilization of streambanks by planting or by revetment construction. One phase of reforestation that may be applied near a reservoir is planting of vegetation screens. Such screens, planted on the flats adjacent to the normal stream channel at the head of a reservoir, reduce the velocity of silt-laden storm inflows that inundate these areas. This stilling action causes extensive deposition to occur before the silt reaches the main cavity of the reservoir.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.10
• /
• pp.1013-1020
• /
• 2008

To evaluate the pollutant removal efficiency and clarify the cause of low removal efficiency of the wetland, temporal and spacial distributions of water quality were investigated at 16 sites in the Sihwa constructed wetland. The removal efficiency showed a tendency to decrease since the construction of the wetland, except for TN. In addition, the efficiency was largely varied with season, especially BOD and TP. No removal efficiency of BOD was observed in April and July when algal bloom was occurred in lower part open water of the wetland. On the other hand, TP showed no removal efficiency from April to August showing -291% of removal efficiency in August. From the horizontal distribution in closed water regions, SS concentration for the central area was significantly higher than for left and right areas(p = 0.013, center > left > right areas). From the results of this study, we infer that anaerobic condition due to the excessive accumulation of organic matters and lack of uniformity of water flow distribution are major factors of the low removal efficiency of the wetland.

• Ecology and Resilient Infrastructure
• /
• v.3 no.4
• /
• pp.315-321
• /
• 2016

To identify the relationship between land use and thermal environment in an urban area, the air temperature was measured at different places of land use, and the changes of land use and air temperature were traced for 40 years in Incheon City. The relationship between land use and temperature was also investigated using satellite image data. The results of temperature measurements on a forest, a cropland (rice paddy), a bareland (school ground), and an urban area (asphalt road) from 19 to 21 August 2014 showed that air temperature was the highest on a pavement road. The temperature increased by about $1.4^{\circ}C$ ($0.035^{\circ}C/year$) for 40 years from 1975 to 2014 in Incheon. The changes in land use patterns of Incheon for the past 40 years showed that urban dry land, bareland and grassland have increased and cultivated land, wetland and forest land have decreased gradually. The land surface temperature (LST) was correlated with the normalized difference vegetation index (NDVI) and normalized difference built-up index (NDBI) extracted from Landsat satellite image. The land surface temperature was lower at higher NDVI, and higher at higher NDBI. Therefore, it is important to conserve and restore the land use of greenery, wetlands, and agricultural land in order to mitigate the heat island effect and improve the thermal environment in an urban area.

• Ecology and Resilient Infrastructure
• /
• v.6 no.4
• /
• pp.191-199
• /
• 2019

Road development is considered an important factor in invasion and dispersion of ailen plants by damaging the natural ecosystems and connecting the detached landscapes into long tubular structures. In this study, vegetation survey was carried out according to the topographical characteristics of cut slope, fill slope, and flat land at the construction site in order to understand the effect of road developemt on the change of the floristic composition of ailen plants. Road developement projects caused a lot of changes in annual and biennial alien plants because of continuous disturbances. Changes in species composition of alien plants decreased in the cut slope. On the other hand, the ailen palnts of the fill slope increased. The increase or decrease alien plants on flat land were identified depending on where it occurred, and no major trend was found. The cause of these change was driven by unintentionally introduced alien plants. In particular, the cut slope with a high occurence of unintentional ailen plants should not be used as a source of high-risk alien plants such as ecosystem disturbances. Since the transplanted species were intentionally planted by the landscape plan, it was possible to identify colonies from early stages and spread to the nearby flat land. Therefore, in order to minimize the impact of road slope vegetation on the surrounding ecosystem during and after road construction, it is suggested to plant high viability plants in the landscape design during the environmental impact assessment consultation.

• Ecology and Resilient Infrastructure
• /
• v.6 no.4
• /
• pp.243-249
• /
• 2019

The purpose of this study is to analyze the reflectance of bed materials according to changes in the water level using a drone-based hyperspectral sensor. For this purpose, we took hyperspectral images of bed materials such as soil, gravel, cobble, reed, and vegetation to compare and analyze the spectral data of each material. To adjust the water level, we constructed an experimental channel to control the discharge and installed the bed materials within the channel. In this study, we configured 3 cases according to the water level (0.0 m, 0.3 m, 0.6 m). After the imaging process, we used the mean value of 10 points for each bed material as analytical data. According to the analysis, each material showed a similar reflectance by wavelength and the intrinsic reflectance characteristics of each material were shown in the visible and near-infrared region. Also, the deeper the water level, the lower the peak reflectance in the visible and near-infrared region, and the rate of decrease differed depending on the bed material. We expect the intrinsic properties of these bed materials to be used as basic research data to evaluate river environments in the future.

• Ecology and Resilient Infrastructure
• /
• v.2 no.2
• /
• pp.108-117
• /
• 2015

This study was carried out to assess problems related to legislative regulations and guidelines concerning some biological assessment systems applied to stream corridor in Korea. We comparatively reviewed the law of stream corridors and the guidelines for master plan concerned, and the law of water quality and health assessment criteria for the aquatic ecosystem concerned. Stream environments were not managed effectively due to the absence of detail regulations and the criteria for stream assessment. A biological assessment system was not equivalently integrated within the management of water resources in process implementation of projects resulting from the dualistic management system for stream corridors in Korea. The current biological assessment system was reflected to mainly physical habitats or only oriented to some aquatic species correlated with water quality. This system was also recognized as part of environment impact assessment based on an intensive survey method of most biological taxa. Conclusively rapid and quantitative assessment techniques based on advanced organisms, such as vegetation, fish and birds, etc. should be urgently provided for considering as representative indicators of stream conditions in Korea.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.11 no.4
• /
• pp.233-246
• /
• 2009

The partitioning of evapotranspiration (ET) into evaporation (E) and transpiration (T) is critical in understanding the water cycle and the couplings between the cycles of energy, water, and carbon. In forests, the total ET measured above the canopy consists of T from both overstory and understory vegetation, and E from soil and the intercepted precipitation. To quantify their relative contributions, we have measured ET from the floors of deciduous and coniferous forests in Gwangneung using eddy covariance technique from 1 June 2008 to 31 May 2009. Due to smaller eddies that contribute to turbulent transfer near the ground, we performed a spectrum analysis and found that the errors associated with sensor separation were <10%. The annual sum of the understory ET was 59 mm (16% of total ET) in the deciduous forest and 43 mm (~7%) in the coniferous forest. Overall, the understory ET was not negligible except during the summer season when the plant area index was near its maximum. In both forest canopies, the decoupling factor ($\Omega$) was about ~0.15, indicating that the understory ET was controlled mainly by vapor pressure deficit and soil moisture content. The differences in the understory ET between the two forest canopies were due to different environmental conditions within the canopies, particularly the contrasting air humidity and soil water content. The non-negligible understory ET in the Gwangneung forests suggests that the dual source or multi-level models are required for the interpretation and modeling of surface exchange of mass and energy in these forests.

• Journal of The Geomorphological Association of Korea
• /
• v.19 no.1
• /
• pp.17-27
• /
• 2012

Coastal dunes help stabilize the coastal landscape and protect the hinterland through dynamic interaction with sand beaches. Sometimes dune erosion occurs during the tropical cyclones, while dune recovery may naturally follow after the event. As the typhoon Kompasu passed through the Korean Peninsula early-September in 2010, it caused a rise in water in association with the storm, wave run-ups, and heavy rains in coastal areas. As the result, coastal dunes along the west coast of Korea were severely damaged during the storm. However, the degree and extent of erosion and recovery of dunes were found to be related with the condition of beach-dune systems including gradients of foreshore and front slope of the dune, sediment supply, vegetation, wind activity, and human interferences. Some dunes retreated landward more and more after the erosional event, while others recovered its original profile by aeolian transport processes mainly during the winter season. Vegetated dunes with pine trees were less recovered after the erosion than grass-covered dunes. In addition, dunes with artificial defense were more eroded and less recovered than those without hard constructions. According to the observation after the severe storm, it is likely that the sand transport process is critical to the dune recovery. Therefore, the interactions between beach and dune must be properly evaluated from a geomorphological perspective for the effective management of coastal dunes, including natural recovery after the erosion by storm events.

• Korean Journal of Remote Sensing
• /
• v.35 no.5_2
• /
• pp.819-829
• /
• 2019

In the disaster of collapse, an immediate response is needed to prevent the damage from worsening, and damage area calculation, response and recovery plan should be established. This requires accurate detection of the damage affected area. This study performed the detection of the damaged area by using UAV which can respond quickly and in real-time to detect the collapse accident. The study area was selected as B-05 housing redevelopment area in Jung-gu, Ulsan, where the demolition of houses and apartments in progress as the redevelopment project began. This area resembles a collapsed state of the building, which clear changes before and after the demolition. UAV images were acquired on May 17 and July 9, 2019, respectively. The changing area was considered as the damaged area before and after the collapse of the building, and the changing area was detected using CVA (Change Vector Analysis) the Representative Change Detection Technique, and SLIC (Simple Linear Iterative Clustering) based superpixel algorithm. In order to accurately perform the detection of the damaged area, the uninterested area (vegetation) was firstly removed using ExG (Excess Green), Among the objects that were detected by change, objects that had been falsely detected by area were finally removed by calculating the minimum area. As a result, the accuracy of the detection of damaged areas was 95.39%. In the future, it is expected to be used for various data such as response and recovery measures for collapse accidents and damage calculation.

• Korean Journal of Plant Resources
• /
• v.23 no.2
• /
• pp.187-196
• /
• 2010

A total of 10 islands (Kumodo and Komundo in Yeosu City; Oinarodo in Goheung County; Chongsando, Soando, and Pogildo in Wando County; Chodo in Jindo County; Uido, Huksando, and Hongdo in Shinan County) were surveyed to confirm distribution of naturalized plants from June 2006 to December 2008. A total of 100 naturalized plants taxa from 25 families were recorded. The highest number of naturalized plant species (82 taxa) was recorded on Oinarodo, while the lowest number was recorded on Hongdo (42 taxa) and on Uido (34 taxa). A total of 26 naturalized species taxa (such as Dactylis glomerata, Lolium perenne, Bromus unioloides, Rumex obtusifolius, Chenopodium album, Phytolacca americana, Barbarea vulgaris, Lepidium apetalum, Robinia pseudo-acacia, Trifolium repens, Erigeron annuus, Erigeron canadensis, Senecio vulgaris, Xanthium strumarium) was recorded in all study areas. Distribution of naturalized plants were categorized into 7 habitat types based on ecological traits: afforested land, beach, port, and vacant land, road boundary, road cut and slope area, waste arable land, landfill area, and wetland. Systematic management is required to conserve unique landscape, species diversity, vegetation and ecosystem of Dadohae National Park. In order to manage the naturalized plants in Dadohae National Park, basic surveys are most needed to understand distribution and dispersal of naturalized plants communities based on ecological features of each habitat type.