• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.161-167
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• 2019

In this paper, the performance verification of an around-view sonar and an excavation depth measuring sonar applicable to track-based ROVs (Remotely Operated underwater Vehicles) for heavy duty work is studied. For the performance verification, an experiment is carried out in a water tank and at sea by attaching the around-view sonar and the excavation depth measuring sonar for a heavy work ROV. In the case of the around-view sonar, image sonars are mounted on ROV in four directions (front, back, left and right) and in the case of the excavation depth measuring sonar, the same kind of MBES (Multi Beam Echo Sounder) is mounted on the front of the ROV. The result of an operation test of the ROV equipped with these sonars shows that the sonar systems are rarely affected by high turbidity due to sedimentation during the operation. In the case of the around-view sonar, it is possible to see rock formation, gravel and sandbank 30 m ahead of the ROV. It is confirmed that the excavation depth can be measured after the ROV has performed the excavation. This experiment demonstrates that the ROV can improve the efficiency of the work by utilizing the around-view sonar and the excavation depth measuring sonar.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.705-713
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• 2020

The present study investigated the temporal changes of river habitats caused by construction and operation of the three large weirs (Sejong, Gongju, and Baekje) in the Geum River. High resolution satellite imagery taken during three periods (preconstruction, before and after gate operation) were used for habitat analysis. We divided bar area into eight habitat types in addition to water area. Then, we identified the nine habitat types from the satellite imagery and estimated each habitat area. Our results show that after weir construction, large bar areas were dramatically decreased and bareland was nearly absent post gate-operation in all three weirs. However, total bar area and bareland were again increased distinctively soon after weir opening events, especially in the uppermost weir, the Sejongbo. These results suggest that weir opening operations provide a relatively simple channel of more diverse through the process of increasing bar area in a river channel.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.639-650
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• 2022

In areas where large-scale sediment transport occurs, it is important to apply appropriate countermeasure method because the phenomenon tends to accelerate by time duration. Among the various countermeasure methods applied so far, beach nourishment needs to be reviewed as an erosion prevention measure because the erosion pattern is mitigated and environmentally friendly depending on the particle size. In the case of beach nourishment. a detailed review is required to determine the size, range, etc., of an appropriate particle diameter. In this study, we investigated the characteristics of the related topographic change using the change in the particle size of nourishment materials, the application of partial area, and the condition under the coexistence of waves and wind as variables because those factors are hard to be analyzed and interpreted within results and limitation of that the existing numerical models are not able to calculate and result out so that it is required that phenomenon or efforts are reviewed at the same time through physical model experiments, field monitoring and etc. So we attempt to reproduce the tendency of beach erosion and deposition and predict possible phenomena in the future using machine learning techniques for phenomena that it is not able to be interpreted by numerical models. we used the hydraulic experiment results for the training data, and the accuracy of the prediction results according to the change in the training method was simultaneously analyzed. As a result of the study it was found that topographic changes using machine learning tended to be similar to those of previous studies in short-term predictions, but we also found differences in the formation of scour and sandbars.

• Korean Journal of Environment and Ecology
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• v.10 no.2
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• pp.211-239
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• 1997

The flora of Oesorak in the Soraksan National Park including Chombongsan(Mountain) and Kwanmobong(Peak) were surveyed from February to August, 1996. These areas have very rich and diverse flora;620 taxa with 89 families, 321 genera, 526 species, 2 subspecies, 89 varieties and 3 forms in the Oesorak, 404 taxa with 251 genera, 350 species, 1 subspecies, 51 varieties and 2 forms in the Chombongsan(Mountain), 286 taxa with 206 genera, 233 species, 1 subspecies, 50 varieties and 2 forms in Kwanmobong(peak). The Oesorak had very distinct floristic characteristics such as the wild habitats of Asarum maculatum(Aristolochiaceae) and Ilex macropoda(Aquifoliaceae). In the phyorgeographical point of view, the six species such as Sapium japonicum (Euphorbiaceae), Euphorbia joldini(Euphorbiaceae), Ilex macropoda (Aquifoliaceae), Styrax japonica (Styracaceae), Carex sideros ticta (Cyperaceae) and Asarum maculatum (Aristolochiaceae) were naturalized into this region, while the 17 taxa such as Abies neprolepis(Pinaceae), Pinus pumila(Pinaceae), Thuja koraiensis(Cupressaceae), Allium senescens(Liliaceae), Lilium distichum(Liliaceae), Saxifraga punctata(Saxfragaceae), Rosa marretii(Rosaceae), Bupleurum euphorbioides(Umbelliferae), Androsace cortusaefolia (Primulaceae), Peducularis mandshurica(Scrophulariaceae) and Leontopodium coreanum (Compositae) were distrivuted to this region. The colonizing weedy species such as Ixris repens (Compositae) were distributed to this region. The colonizing weedy species losa(Labiatae) and Rosa rugosa(Rosaceae) were naturalized into ca. 900m at sea level mainly due to the sand soil from the seashore. Mountain roadbed is susceptible than other areas to the slippery road problems, due largely to snow and rain, particularly during winter. Sand soils from seashore are utilized to minimize this slip in traffic operation.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.461-474
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• 2005

Physicochemical parameters, plankton community structure, and sediment were surveyed from 1988 to 2002, at two months interval, in a eutrophic coastal lagoon (Lake Songji, Korea). The lake basin is separated from the sea by a narrow sand dune, and a shallow sill divides the lake basin into two sub-basins. The stable stratifications and chemoclines are maintained all through the year at 1-2 m depth. DO was often very low (<1 $mgO_2\;{\cdot}\;L^{-1}$) in the monimolimnion. Secchi disc transparency was in the range of 0.5-2.7 m. TP, TN, and Chl. a concentration in the mixolimnion were 0.015-0.396 $mgP\;{\cdot}\;L^{-1}$), 0.223-3.521 $mgN\;{\cdot}\;L^{-1}$, and 0.5-129.8 mg ${\cdot}\;m^{-3}$, respectively. TSI was in the eutrophic range of 54 to 62. Sediment was composed of silt and coarse silt. COD, TP, and TN content of the sediment were 51.4-116.9 $mgO_2\;{\cdot}\;gdw^{-1}$, 0.04-1.46 $mgP\;{\cdot}\;gdw^{-1}$ and, 0.12-1.03 $mgN\;{\cdot}\;gdw^{-1}$, respectively. The 49 phytoplankton species were identified. The maximum phytoplankton abundance obscured the lake in September 2001 (max. density: 23,350 cells ${\cdot}\;mL^{-1}$. The Chlorophyte Schroederia judayi was dominant species in summer (max. density: 20,417 cells ${\cdot}\;mL^{-1}$). The lake showed unique limnological features of a brackish lagoon in respect to biological community, chemical characteristics, and physical phenomena.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.318-326
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• 2017

Riverine wetlands were reduced and damaged by dredging of rivers and constructing parks in wetlands by Four Rivers Project from 2008 to 2013. Therefore, replacement wetlands were constructed for the compensation of wetland loss by the government. However, It is not enough to manage replacement wetlands. In order to manage the wetlands efficiently, it is necessaty to assess the functions of the wetlands and to manage them according to their functions. Here we performed functional assessments for a replacement wetland called Gangcheon wetland using the modified HGM approach. Hydrological, biogeochemical, animal habitat, and plant habitat functions for the wetland were assessed. To assess the functions, we collected informations for modified HGM approach from the monitored hydrologic data, field survey, published reports and documents for before and after the project, and hydraulic & hydrologic modeling. As the results of the assessment, the hydrological function for the replacement wetland showed 65.5% of the reference wetland, biogeochemical function showed 66.6%, plant habitat function showed 75%, and animal habitat function showed 108.3%. Overall, Gangcheon wetland function after the project was reduced to 78.9% of the function before the project. The decrease in hydrological function is due to the decrease of subsurface storage of water. And the decrease in biogeochemical & pland habitat functions is due to the removal of sandbank around the Gangcheon wetland. To compensate for the reduced function, it is necessary to expand the wetland area and to plant the various vegetation. The modified HGM used in this study can take into account the degree of improvement for replacement wetlands, so it can be used to efficiently manage the replacement wetlands. Also when the wetland is newly constructed, it will be very useful to assess the change of function of the wetland over time.

• Journal of the Korean Institute of Landscape Architecture
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• v.47 no.1
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• pp.26-38
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• 2019

This study is based on the analysis of the characteristics of waterfront scenery. Recently, waterfront development has expanded residentially, commercially and into leisure space. In the development of the waterfront, it is necessary to apply designs suitable for urban and various other waterfront areas. In this study, the natural scenery of the waterfront was researched with respect to the Korean Jingyeong landscape paintings and the main elements of the scenery were analyzed. In this study, 105 painting of Korean Jingyeong landscapes paintings were selected for the analysis of the waterside scenery. The paintings of Jeong Seon were studied to categorize streams topographically into mountainous, upper, middle, lower, and ocean types. In addition, major micro-topography elements, which are 13 water image elements and 13 staffage elements were analyzed. The main waterfront landscape elements are divided into 13 types. The waterfalls were divided into long waterfalls, short waterfalls, cascading waterfalls, and other aspects considered were line stream, curve stream, multi-curve stream, pond, water surface, flow surface, wave surface, rock side, pile sandy side, sandy side. There are 13 kinds of staffage elements, include pine forest, pine trees, fir trees, bamboo trees, willow trees, broadleaf tree, villages, houses, gazebo, boat, bridges, and people. The waterfront landscape by a river area was explained according to each characteristic of the waterfront landscape and staffage, and their changes were analyzed in each area. The 105 paintings were divided into 35 pieces of mountainous streams, 9 upper streams, 5 middle streams, 35 lower streams, and 21 oceans, and the change of each waterfront landscape and staffage was analyzed. Based on the topographical analysis of the waterfront landscape and staffage, the results can be summarized into 5 types of the waterfront landscape. Based on the micro-topographical characteristics of the waterfront landscape styles are as follow. In the mountainous streams, long waterfall and deep forest type are apparent, which depicts deep mountain waterfall scenery, and a multi-stream forest is the scenery of a picnic in the mountains, which is a representative form of mountainous streams landscape. In the upper-middle stream, the water-surface and gazebo type is predominant. In the lower stream, the sandy-gazebo typ scenery is predominant and the sandy depiction is unique to lower stream landscape. Pile sandy-dock type is life scenes where human activity highlighted, is a representative form of the lower stream landscapes. The characteristic of the coastal landscape is the serpentine rock scenery on the beach and the wave-serpentine rock type that forms the main coastal landscape. The study aims to propose significant design elements for a natural waterfront landscape planning based on the analysis of landscape in the paintings of Jeong Seon.

• Journal of Environmental Impact Assessment
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• v.32 no.6
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• pp.389-406
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• 2023

The research area, located in the northern coastal region of South Korea's West Sea, involves three bird habitats. Among these are two newly established habitats in Songdo International Business District, created by filling and developing tidal flats that were previously utilized as stopover sites for migratory birds. One of these areas showed decrease (Residual tidal flats, site.1) while the other showed increase (Artificial lake, site.2) in bird influx. The third habitat (Namdong reservoir, site.3) is a pre-existing stable habitat which has been maintained as a stable habitat. This study conducts an assessment of habitats based on avian population clusters and environmental surveys and proposes habitat management measures. A survey of bird populations and habitat environments was conducted for a total of 39 occasions from January to December 2022. The observed bird species totaled 14 families and 48 species with 20,760 individuals. Compared to the existing habitats, the newly established habitats showed relatively lower influx of bird species and individuals. During the habitat assessment, the newly established habitats were rated as I to II grade, while the existing habitat was rated as relatively high III grade on the grading assessment of the tidal flat. An analysis of habitat types revealed that the existing habitat, in which diverse strategies for habitat type diversity and mitigating anthropogenic interference were demonstrated, attracted a diverse range of bird species. Through this research, it was deduced that the diversity of habitat types plays a significant role in attracting various bird species. Upon evaluation of habitat types concerning the habitat characteristics of the bird species selected for habitat management, as habitat management measures, it is deemed that the creation of shielded green areas (referred to as 'buffer green') to minimize interference from the surroundings, the establishment of reed fields (site.1, 2) positively correlated with reservoirs, and the improvement of sandbanks (site.1) positively associated with tidal flats, the two relations which we drew from correlation analysis between occurrence species and habitat types, would contribute to the future restoration and maintenance of stable habitats. The results of this study can be applied not only to the study area but also to other development zones, such as coastal reclamation sites, which share similar geographical and environmental characteristics, including arrival sites for migratory birds.