• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.687-697
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• 2019

By monitoring sediment grain size and level variation of tidal flat surface for 6 years (2005-2011), and also by mooring TISDOS (tidal-flat sediment dynamics observation system) on the low intertidal flat in 2008, we investigated the sedimentary environment of tidal flat in the dammed Yeongsan River Estuary. The tidal flat of the Yeongsan River Estuary lost 82 % of its area because of coastal development projects, and a narrow tidal flat below mean sea level now remains. Most of the tidal flat sediments are composed of silt up to 70-94 %, and show the characteristics of clay deficiency and silt dominance. This is closely related with the coastal development, which led to the destruction of high tidal flats where most mud settled, and the modification of tidal current patterns. Moreover, the estuarine tidal-flat sediments reveal seasonal variation. They are coarse with abundant silt during windy autumn to spring, fine with abundant clay during the less-windy and high-discharge summer. This phenomenon indicates that the behavior of sediment particles on the low intertidal flats of the Yeongsan River Estuary is influenced by wind waves for silt and fresh water discharge and the tidal process for clay. Monitoring results of the altitude of tidal flat surface showed that the study area had eroded at an average rate of -2.6 cm/y during the period of 2005-2011, and also that an unusual deposition with a rate of 4 cm/y occurred in 2010. The erosion can be explained by an increased tidal amplitude and a strengthened ebb-dominant tidal asymmetry after the construction of an estuary dike and the Yeongam Kumho Seawall. The deposition in 2010 seems to have been closely related to the mass production of suspended materials from dredging of the estuary.

• Korean Journal of Environment and Ecology
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• v.34 no.4
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• pp.334-344
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• 2020

A total of 24 families, 44 species, and 658 benthic macroinvertebrates were identified, and Ecdyonurus dracon Kluge (13%) was the dominant species in forested streams within the Yeonyeopsan (Mt.). A total of four habit categories (i.e., clingers (56%), burrowers (19%), swimmers (14%), and sprawlers (56%)) were identified, and clingers were the dominant habit at all survey points except point one (UP1). Habitat characteristics were depended on the hydraulic factors (e.g., flow velocity, depth, and substrates), water quality (e.g., DO and water temperature), and the habitat characteristics were differed in the riffle, which has a faster the flow velocity, compared by in the stagnant pool. In other words, in riffles, the clingers dominated in high flow velocity with the large maximum and median grain size for substrates in the habitats regardless of depth, but the burrowers and sprawlers were dominant in low flow velocity with the small maximum and median grain size for substrates in the habitats. Moreover, DO and flow velocity were in positive correlation (y = 0.6666x - 0.659, R² = 0.0851), and the habitat for burrowers was wider than that for sprawlers or clingers. The water depth was negatively correlated with water temperature (y = -26.397x + 283.87, R² = 0.1802) since the water temperature is more sensitive to insolation in shallow depth. pH was positively correlated with water temperature. The investigation of the habitat characteristics by separating the relations between pH and DO in upstream and downstream showed the low pH and high DO in the upstream with a high crown density of 68%, regardless of community composition. On the other hand, high pH and low DO in the downstream with a relatively low crown density of 51%. It was considered that the riparian forest played a role in suppressing the growth of attached algae and the controlling water temperature in headwater streams. Our findings identified the habitat characteristics of benthic macroinvertebrates in a headwater stream. We expected that the finding can provide reference data for suggesting conservation and management plans in a headwater stream and increasing academic value.

• Journal of Environmental Policy
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• v.8 no.1
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• pp.73-95
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• 2009

The fact that soil loss causing to increase muddy water and devastate an ecosystem has been appearing upon a hot social and environmental issues which should be solved. Soil losses are occurring in most agricultural areas with rainfall-induced runoff. It makes hydraulic structure unstable, causing environmental and economical problems because muddy water destroys ecosystem and causes intake water deterioration. One of three severe muddy water source areas in Soyanggang-dam watershed is Jawoon-ri region, located in Hongcheon county. In this area, many cash-crops are planted at illegally cultivated agricultural fields, which were virgin forest areas. The purpose of this study is to estimate soil loss with current land uses(including illegal cash-crop cultivation) and soil loss reduction with land use conversion from illegal cultivation back to forest. In this study, the Sediment Assessment Tool for Effective Erosion Control(SATEEC) ArcView GIS was utilized to assess soil erosion. If the illegally cultivated agricultural areas are converted back to forest, it would be expected to 17.42% reduction in soil loss. At the Jawoon-ri region, illegally cultivated agricultural areas located at over 30% and 15% slopes take 47.48 ha(30.83%) and 103.64 ha(67.29%) of illegally cultivated agricultural fields respectively. If all illegally cultivated agricultural fields are converted back to forest, it would be expected that 17.41% of soil erosion and sediment reduction, 10.86% reduction with forest conversion from 30% sloping illegally agricultural fields, and 16.15% reduction with forest conversion from 15% sloping illegally agricultural fields. Therefore, illegally cultivated agricultural fields located at these sloping areas need to be first converted back to forest to maximize reductions in soil loss reduction and muddy water outflow from the Jawoon-ri regions.

• Geophysics and Geophysical Exploration
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• v.7 no.3
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• pp.164-173
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• 2004

To delineate geothermal water movement at the Pohang geothermal development site, Self-Potential (SP) survey and monitoring were carried out during pumping tests. Before drilling, background SP data have been gathered to figure out overall potential distribution of the site. The pumping test was performed in two separate periods: 24 hours in December 2003 and 72 hours in March 2004. SP monitoring started several days before the pumping tests with a 128-channel automatic recording system. The background SP survey showed a clear positive anomaly at the northern part of the boreholes, which may be interpreted as an up-flow Bone of the deep geothermal water due to electrokinetic potential generated by hydrothermal circulation. The first and second SP monitoring during the pumping tests performed to figure out the fluid flow in the geothermal reservoir but it was not easy to see clear variations of SP due to pumping and pumping stop. Since the area is covered by some 360 m-thick tertiary sediments with very low electrical resistivity (less than 10 ohm-m), the electrokinetic potential due to deep groundwater flow resulted in being seriously attenuated on the surface. However, when we compared the variation of SP with that of groundwater level and temperature of pumping water, we could identify some areas responsible to the pumping. Dominant SP changes are observed in the south-west part of the boreholes during both the preliminary and long-term pumping periods, where 3-D magnetotelluric survey showed low-resistivity anomaly at the depth of $600m\~1,000m$. Overall analysis suggests that there exist hydraulic connection through the southwestern part to the pumping well.

• Journal of Korean Society of Forest Science
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• v.101 no.3
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• pp.333-343
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• 2012

In-stream large wood (LW) has a critical impact on the geomorphic characteristics relevant to ecosystem management and disaster prevention, yet relatively little is known about variations in its dynamics and subsequent export on the watershed-scale perspective in Korea. Here we review variations in the dynamics and subsequent export of LW as a function of stream size, which is appropriate for Korean mountain streams. In upstream channels with narrow bankfull widths and low stream discharges, a massive amount of LW, resulting from forest dynamics and hillslope processes, may persist for several decades on valley floor. These pieces, however, are eventually transported during infrequent debris flows from small tributaries, as well as peak hydrology in main-stem channels. During the transport, these pieces suffer fragmentation caused by frictions with boulders, and stream bank and bed. Although infrequent, these events can be dominant processes in the export of significant amounts of LW from upstream channel networks. In downstream channels with wide bankfull widths and high stream discharges, LW is dominantly recruited by forest dynamics and bank erosion only at locations where the channel is adjacent to mature riparian forests. With the LW pieces that are supplied from the upstream, these pieces are continuously transported downstream during rainfall events. This leads to further fragmentation of the LW pieces, which increases their transportability. With decreasing stream-bed slope, these floated LW pieces, however, can be stored and form logjams at various depositional sites, which were developed by interaction between channel forms and floodplains. These pieces may decay for decades and be subsequently transported as particulate or dissolved organic materials, resulting in the limitation of LW fluvial export from the systems. However, in Korea, such depositional sites were developed in the extremely limited streams with a large dimension and no flood history for decades, and thus it does not be expected that the reduction of LW export amount, which can be caused by the long-term storage. Our review presents a generalized view of LW processing and is relevant to ecosystem management and disaster prevention for Korean mountain streams.

• Journal of the Korean association of regional geographers
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• v.6 no.3
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• pp.37-52
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• 2000

Generally speaking, the metropolitan agricultural regions have some advantages from the high accessibility to markets. But agriculture inevitably rests on the biological process. This study shows what characteristics of the agricultural management are found in these less favored metropolitan areas with bad natural conditions and how farm household live there. From the view point of farm household, the quality of labors they can get is quite low, and insufficient in quantity. The shortage of labor can be made up for the farming on Trust Farming System And the relatively less favored agricultural conditions prevent people from immigrating into these kind of areas, if they don't have any relationship with there. With bad natural conditions, the farm households usually cultivate relatively small areas for the purpose of self-sufficiency, and with smaller cultivating units(Baemi) of the land than in open fields. The scale of the agricultural management is largely affected by the ages of agricultural managers. The more aged the managers are, the smaller scale of the agricultural management. How to use lands is determined in accordance with the natural conditions such as percentage of sunshine and accessibility to drainage facilities -the two major factors- and more. Either owner-run farmlands or leased farmlands doesn't show any difference in each growing crops. Depending on the conditions of the lands, rice paddy is used for growing rice and field is used for growing self sufficient plants including vegetables for the farm household. Although the lack of infrastructure causes the inconvenience of living, and there exist less favored agricultural conditions, this kind of life and agricultural management style -self-sufficiency type- seems to be sustained quite longer. The less favored natural conditions for farming keeps the agricultural management style from being developed to be the level of commercialization. And the poor economic situation of farmers are continuing again and again. With the result of this study, there should be two conditions to be established previously if they want to develop these regions. First, each farm household should get to know of the importance of commercialization and try to spread it. The commercialization. should be attained through the expansion of the environmental friendly agriculture and the improvement of the previously established distribution system of the crops. Secondly, there should be a support from the government. The support will include the expansion of the infrastructures for fanning to improve the fanning conditions and the compensation system directly from the government to the farmers.

• Journal of the Korean Geographical Society
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• v.31 no.3
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• pp.469-488
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• 1996

The defining of weather forecasting regions is possible. since the representativeness of regional weather can by reasonably clarified in terms of weather entropy and the use of information ratio. In this paper, the weather entropy and information ratio were derived numerially from using the information theory. The typical weather characteristics were clarified and defined in the homogeneous weather forecasting regions of the southern parts of Korea. The data used for this study are the daily precipitation and cloudiness during the recent five years (1990-1994) at 42 stations in southern parts of Korea. It is divided into four classes of fine, clear, cloudy and rainy. The results are summarized as follows: 1. The maximum value of weather entropy in study area is 2.009 vits in Yosu in July, and the minimum one is 1.624 bits in Kohung in October. The mean value of weather entropy is maximal in July, on the other hand, minimal in October during four season. The less the value of entropy is, the stabler the weather is. While the bigger the value of entropy is, the more changeable the weather is. 2. The deviation from mean value of weather entropy in southern parts of Korea, with the positive and the negative parts, shows remarkably the distributional tendency of the east (positive) and the west (negative) in January but of the south (positive) and the north (negative) in July. It also clearly shows the distributional tendency of the east (postive) and the west(negative) in the coastal region in April, and of X-type (southern west and northern east: negative) in Chiri Mt. in October. 3. In southern parts, the average information ratio maximaly appear 0.618 in Taegu area in July, whereas minimally 0.550 in Kwangju in October. Particularly the average information ratio of Pusan area is the greatest in April, but the smallest in October. And in Taegu, Kwangju, and Kunsan, it is the greatest in April, January, and July, but the smallest in Jyly, July, and pril. 4.The narrowest appreance of weather representativeness is in July when the Kwangju is the center of the weather forecasting. But the broadest one is in April when Taegu is the center of weather forecasting. 5. The defining of weather forecasting regions in terms of the difference of information ratio most broadly shows up in July in Pusan including the whole Honam area and the southern parts of Youngnam when the Pusan-Taegu is the basis of the application of information ratio. Meanwhile, it appears most broadly in January in Taegu including the whole southern parts except southern coastal area.

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.79-86
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• 2004

Hydraulic conductivity along rock fracture is mainly dependent on fracture geometries such as orientation, aperture, roughness and connectivity. Therefore, it needs to consider fracture geometries sufficiently on a fracture model for a numerical analysis to calculate permeability coefficient in a fracture. This study performed new type of numerical analysis using a homogenization analysis method to calculate permeability coefficient accurately along single fractures with several fracture models that were considered fracture geometries as much as possible. First of all, fracture roughness and aperture variation due to normal stress applied on a fracture were directly measured under a confocal laser scaning microscope (CLSM). The acquired geometric data were used as input data to construct fracture models for the homogenization analysis (HA). Using the constructed fracture models, the homogenization analysis method can compute permeability coefficient with consideration of material properties both in microscale and in macroscale. The HA is a new type of perturbation theory developed to characterize the behavior of a micro inhomogeneous material with a periodic microstructure. It calculates micro scale permeability coefficient at homogeneous microscale, and then, computes a homogenized permeability coefficient (C-permeability coefficient) at macro scale. Therefore, it is possible to analyze accurate characteristics of permeability reflected with local effect of facture geometry. Several computations of the HA were conducted to prove validity of the HA results compared with the empirical equations of permeability in the previous studies using the constructed 2-D fracture models. The model can be classified into a parallel plate model that has fracture roughness and identical aperture along a fracture. According to the computation results, the conventional C-permeability coefficients have values in the range of the same order or difference of one order from the permeability coefficients calculated by an empirical equation. It means that the HA result is valid to calculate permeability coefficient along a fracture. However, it should be noted that C-permeability coefficient is more accurate result than the preexisting equations of permeability calculation, because the HA considers permeability characteristics of locally inhomogeneous fracture geometries and material properties both in microscale and macroscale.

• Journal of Wetlands Research
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• v.16 no.4
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• pp.379-388
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• 2014

A sewage was treated using a serially combined vertical(VFCW) and horizontal flow double media (sand and zeolite for VFCW and sand and waste oyster-shell for HFCW) reed constructed wetland(HFCW) with intermittent feeding (see Fig. 1). The sewage was fed into the reed constructed wetland for 10 minutes every 6 hours at the hydraulic load of $314L/m^2{\cdot}day$. The summarized results were as follows: pH values in the effluent depended very heavily on oyster-shell height filled in the HFCW. They were maintained at less than pH 6.24 when the height of the oyster-shell layer was 200 mm. Influent DO(oxygen demand) values(average 0.19 mg/L) were increased in the VFCW(average 7.65 mg/L) and decreased again in the HFCW(average 6.49 mg/L). They were higher in the winter than in the summer. The OTR(oxygen transfer rate) was $57.15g\;O_2/m^2{\cdot}day$ in the VFCW and $5.65g\;O_2/m^2{\cdot}day$ in the HFCW. The removal efficiency of $NH_4{^+}$-N was 80.17%(6.01 $NH_4{^+}$-N mg/L in the effluent). It was lower than that in the case where only zeolite was filled in the reed constructed wetland. But it was expected that treated sewage effluent using a double media reed constructed wetland with 300 mm zeolite layer could stably meet the Korean treated sewage effluent standard(20 mg T-N/L). Average removal efficiencies were SS 88.09%, BOD 88.12%, $COD_{Cr}$ 83.11%, $COD_{Mn}$ 85.58%, T-N 57.21%, $NH_4{^+}$-N 80.17%, T-P 86.73%. Nearly, The concentration of $NO_3{^-}$-N in the effluent of the VFCW was decreased in that of the HFCW. More than half of T-N in the effluent was $NO_3{^-}$-N(7.92 mg/L) but the concentration of $NO_2{^-}$-N in the effluent was average 0.90 mg/L. The removal efficiencies of T-P were 93.24%, 86.30% and 55.44% at the height of the oyster-shell-filled constructed wetland of 800 mm, 500 mm and 200 mm, respectively and therefore, they were proportional to oyster-shell height filled in the HFCW.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.5
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• pp.253-261
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• 2015

In this study, Chlorophyll-a (chl-a) prediction model and multiple parameters affecting algae occurrence in Mulgeum site were evaluated by statistical analysis using water quality, hydraulic and climate data at Mulgeum site (1998~2008). Before the analysis, control chart method and effect period of typhoon were adopted for improving reliability of the data. After data preprocessing step two methods were used in this study. In method 1, chl-a prediction model was developed using preprocessed data. Another model was developed by Method 2 using significant parameters affecting chl-a after data preprocessing step. As a result of correlation analysis, water temperature, pH, DO, BOD, COD, T-N, $NO_3-N$, $PO_4-P$, flow rate, flow velocity and water depth were revealed as significant multiple parameters affecting chl-a concentration. Chl-a prediction model from Method 1 and 2 showed high $R^2$ value with 0.799 and 0.790 respectively. Validation for each prediction model was conducted with the data from 2009 to 2010. Training period and validation period of Method 1 showed 20.912 and 24.423 respectively. And Method 2 showed 21.422 and 26.277 in each period. Especially BOD, DO and $PO_4-P$ played important role in both model. So it is considered that analysis of algae occurrence at Mulgeum site need to focus on BOD, DO and $PO_4-P$.