• Economic and Environmental Geology
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• v.50 no.6
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• pp.445-466
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• 2017

Yeongdong area is located in the contact zone between central southeastern Ogcheon belt and Yeongnam massif, in which Cretaceous Yeongdong basin exists. Therefore, the study area has complex geological environment of various geological age and rock types such as Precambrian metamorphic rocks, age-unknown Ogcheon Supergroup, Paleozoic/Mesozoic sedimentary rocks, Mesozoic igneous rocks and Quaternary alluvial deposits. This study focuses on the link between the various geology and water type, and discussed the source of some major ions and their related water-rock interaction. For this study, the field parameters and ion concentrations for twenty alluvial/weathered and eighty bedrock aquifer wells were used. Statistical analysis indicates that there was no significant differences in groundwater quality between wet and dry seasons. Although various types were observed due to complex geology, 80 to 84 % of samples showed $Ca-HCO_3$ water type. Some wells placed in alluvial/weathered aquifers of Precambrian metamorphic and Jurassic granitic terrains showed somewhat elevated $NO_3$ and Cl concentrations. $Mg-HCO_3$ typed waters prevailed in Cretaceous Yeongdong sedimentary rocks. The deeper wells placed in bedrock aquifers showed complicated water types varying from $Ca-HCO_3$ through $Ca-Cl/SO_4/NO_3$ to $Na-HCO_3$ and Na-Cl type. Groundwater samples with $Na-HCO_3$ or Na-Cl types are generally high in F concentrations, indicating more influences of water-rock interaction within mineralized/hydrothermal alteration zone by Cretaceous porphyry or granites. This study revealed that many deep-seated aquifer had been contaminated by $NO_3$, especially prominent in Jurassic granites area. Based on molar ratios of $HCO_3/Ca$, $HCO_3/Na$, Na/Si, it can be inferred that Ca and $HCO_3$ components of most groundwater in alluvial/weathered aquifer wells were definitely related with dissolution of calcite. On the other hand, Ca and $HCO_3$ in bedrock aquifer seem to be due to dissolution of feldspar besides calcite. However, these molar ratios require other mechanism except simple weathering process causing feldspar to be broken into kaolinite. The origin of $HCO_3$ of some groundwater occurring in Cretaceous Yeongdong sedimentary rock area seems to be from dissolution of dolomite($MgCO_3$) or strontianite($SrCO_3$) as well.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.177-185
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• 2005

Data from 122 pumping tests were obtained from 100 boreholes in granites, volcanic rocks, metamorphic rocks, and Cretaceous and Tertiary sedimentary rocks, and then were analyzed using AQTESOLV. Results from 86 of the 122 tests ($71\%$) have an analytical solution corresponding to Theis (1935), Cooper-Jacob (1946), Papadopulos-Cooper (1967), Hantush (1962), Moench (1985), or Hantush-Jacob (1955), whereas the remaining 36 results ($29.5\%$) do not correspond to any of the analytical methods. Of the 86 results, only 17 match the Theis and Cooper-Jacob methods, indicating that the basic methods fer pumping test analysis are useful far only $14\%$ of the total data. This suggests that analytical solutions derived using leaky boundary conditions are appropriate for the analysis of pumping test data in fractured aquifers in this study. Furthermore, the results show the importance of carefully selecting an appropriate model for the analysis of pumping test data. Results from the 122 pumping tests were also analyzed using the GRF model. Using the Barker method, the results show that 77 of the 122 tests ($63\%$) have dimensions ranging between 1.1-2.9. Of these 77 solutions, ($39(44.2{\%})$) have a fractional dimension of 1.1-1.9, ($26(6.5{\%})$) show 2-dimensional radial flow also applicable to the Theis method, and ($38(49.3{\%})$) have dimensions of 2.1-2.9. The results show that groundwater flows according to a fractional flow dimension in fractured aquifers.

• Journal of Korean Society of Forest Science
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• v.39 no.1
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• pp.1-34
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• 1978

On July 8, 1977, 432mm of precipitation which is the largest daily storm in Korea fell on the city of Anyang where a nearby suburban community of Seoul. Average storm intensities of 90mm per hour were recorded during the period from 1900~2200 hours on this date. Area of landslides triggered by this storm is about 96 hectares resulting from 1,876 places within about 12,600 hectares of the watershed studied. These hazards injured hundreds of human lives and took 122 human lives. Rail and highway systems were disrupted and about 30 hectares of rice paddies were washed away and hundreds of hectares were inundated. About 500 houses were destroyed. The objectives of this study are (a) to describe the problem areas, identifying critical factors causing the landslide hazards including earth and stone-debris avalanches, (b) suggest measures which might enhance the effectiveness of stabilization measures, and (c) also suggest the landslide and flood damage prevention methods from the point view of the upper-watershed conservation techniques in Anyang hollow-basin.

• The Journal of Engineering Geology
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• v.22 no.4
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• pp.427-437
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• 2012

A total of 100 groundwater samples were collected from the Nonsan area and the behaviors of uranium and radon as natural radionuclides were investigated with respect to other physicochemical components in the groundwater in order to understand their occurrence, properties, and origins. Radionuclide levels were used to construct detailed concentration maps. The concentration of uranium ranges from 0 to 378 ${\mu}g/L$, with an average of 8.57 ${\mu}g/L$, standard deviation of 42.88 ${\mu}g/L$, and median of 0.56 ${\mu}g/L$. The correlation coefficient between uranium and radon is 0.42, whereas these radionuclides show no relation with other physicochemical components in groundwater. It is noteworthy that the uranium level in most samples (97% of the samples) is less than 30 ${\mu}g/L$, where the bedrock of the aquifer is granite or complex rocks located along the boundary between granite and metamorphic rocks. In the Okcheon metamorphic belt, the uranium concentration of most groundwater is less than 1 ${\mu}g/L$. Radon levels varies from 128 to 9,140 pCi/L, with an average of 2,186 pCi/L, standard deviation of 1,725 pCi/L, and median of 1,805 pCi/L. High radon levels (> 4,000 pCi/L) are most common in regions of Jurassic granite, whereas low radon areas are found in regions of sedimentary rock. In conclusion, the distribution and occurrence of radionuclides are intimately related to the basic geological characteristics of the rocks in which the radiogenic minerals are primarily contained.

• 한국지구물리탐사학회:학술대회논문집
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• 2000.09a
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• pp.54-69
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• 2000

There are groundwater trouble by high-salinity yield inducing sea-water intrusion in Cheju Island. It is used groundwater-GIS(Well-lnfo) in the maintenance and management of groundwater in Cheju Island to grasp groundwater trouble area and cause of high-salinity yield. For 16 wells certain to yield high-salinity, we logged specific electrical conductivity(EC) and tried to get hold of freshwater and saltwater relationship. As result of distribution of $Cl^-$ by depth, it is showed up groundwater trouble by high-salinity yield in the east coastal area and the partly north coastal area. The reason of high-salinity groundwater yield are low-groundwater level by the structure of geology and low-hydraulic gradient etc. There is necessity for management to development and use of groundwater in the high-salinity area, special management area.

• Journal of Korea Water Resources Association
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• v.54 no.10
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• pp.819-833
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• 2021

This study is to evaluate applicability of linkage modeling using PHABSIM (Physical Habitat Simulation System) and SWAT (Soil and Water Assessment Tool) and to estimate ecological flow for target fishes of Andong downstream (4,565.7 km²). The SWAT was established considering 2 multi purpose dam (ADD, IHD) and 1 streamflow gauging station (GD). The SWAT was calibrated and validated with 9 years (2012 ~ 2020) data of 1 stream (GD) and 2 multi-purpose dam (ADD, IHD). For streamflow and dam inflows (GD, ADD and IHD), R², NSE and RMSE were 0.52 ~ 0.74, 0.48 ~ 0.71, and 0.92 ~ 2.51 mm/day respectively. As a result of flow duration analysis for 9 years (2012 ~ 2020) using calibrated streamflow, the average Q185 and Q275 were 36.5 m³/sec (-1.4%) and 23.8 m³/sec (0%) respectively compared with the observed flow duration and were applied to flow boundary condition of PHABSIM. The target stream was selected as the 410 m section where GD is located, and stream cross-section and hydraulic factors were constructed based on Nakdong River Basic Plan Report and HEC-RAS. The dominant species of the target stream was Zacco platypus and the sub-dominant species was Puntungia herzi Herzenstein, and the HSI (Habitat Suitability Index) of target species was collected through references research. As the result of PHABSIM water level and velocity simulation, error of Q185 and Q275 were analyzed -0.12 m, +0.00 m and +0.06 m/s, +0.09 m/s respectively. The average WUA (Weighted Usable Area) and ecological flow of Zacco platypus and Puntungia herzi Herzenstein were evaluated 76,817.0 m²/1000m, 20.0 m³/sec and 46,628.6 m²/1000m, 9.0 m³/sec. This results indicated Zacco platypus is more adaptable to target stream than Puntungia herzi Herzenstein.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.565-582
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• 2018

We investigated the hydrochemical properties of ChusanYongchulso Spring located in Buk-myeon, Ulleung Island, focusing on the formation and characteristics of aquifers in and around the Nari caldera. Abundant pumice with high permeability and numerous fractures (including faults and joints) that formed as a result of caldera subsidence are widely distributed in the subsurface, favoring the formation of aquifers. Because of the presence of porous pyroclastic rocks with a high internal surface area, the water type of the springs is characterized by $NaHCO_3$, with upper stream waters and the upper spring being characterized by $NaHCO_3$ and NaCl, respectively. Components with a high coefficient of determination with EC are $HCO_3$, Na, F, Ca, Mg, Cl, $SiO_2$, and $SO_4$. The high concentrations of Na and Cl might be attributable to the main lithologies in the area, given that alkaline volcanic rocks are distributed extensively across Ulleung Island. Eh and pH, which are considered to be important indicators of water-rock interaction, are unrelated to most components. According to the results obtained from factor analysis, the variance explained by factor 1 is 54% and by factor 2 is 25.8%. Components with a high loading on factor 1 are F, Na, EC, Cl, $HCO_3$, $SO_4$, $SiO_2$, Ca, $NO_3$, and Mg, whereas components with a high loading on factor 2 are Mg and Ca, along with K, $NO_3$, and DO with negative loadings. It is suggested that the high concentrations of Na, Cl, F, and $SO_4$ are closely related to the presence of fine-grained alkaline pyroclastic rocks with high permeability and porosity, which favorintensewater-rock interaction. However, a wide-ranging investigation that encompasses methods such as geophysical prospecting and geochemical analysis (including isotope, trace-element, and tracer techniques) will be necessary to gain a better understanding of the groundwater chemistry, aquifer distribution, and water cycling of Ulleung Island.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.629-641
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• 2021

In this study, a two-dimensional numerical model (Nays2DH) was applied to analyze the process of morphological changes in the river channel bed depending on the changes in the amount of flooding after fully opening the Sejong weir, which was constructed upstream of the Geum River. For this, numerical simulations were performed by assuming the flow conditions, such as a non-uniform flow (NF), unsteady flows (single flood event, SF), and a continuous flood event (CF). Here, in the cases of the SF and CF, the normalized hydrograph was calculated from real flood events, and then the hydrograph was reconfigured by the peak flow discharge according to the scenario, and then it was employed as the flow discharge at the upstream boundary condition. In this study, to quantitatively evaluate the morphological changes, we analyzed the time changes in the bed deformation the bed relief index (BRI), and we compared the aerial photographs of the study area and the numerical simulation results. As simulation results of the NF, when the steady flow discharge increases, the ratio of lower width to depth decreases and the speed of bar migration increases. The BRI initially increases, but the amount of change decreased with time. In addition, when the steady flow discharge increases, the BRI increased. In the case of SF, the speed of bar migration decreased with the change of the flow discharge. In terms of the morphological response to the peak flood discharge, the time lag also indicated. In other words, in the SF, the change of channel bed indicates a phase lag with respect to the hydraulic condition. In the result of numerical simulation of CF, the speed of bar migration depending on the peak flood discharges decreased exponentially despite the repeated flood occurrences. In addition, as in the result of SF, the phase lag indicated, and the speed of bar migration decreased exponentially. The BRI increased with time changes, but the rate of increase in the BRI was modest despite the continuous peak flooding. Through this study, the morphological changes based on the hydrological characteristics of the river were analyzed numerically, and the methodology suggested that a quantitative prediction for the river bed change according to the flow characteristic can be applied to the field.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.257-270
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• 2022

This study evaluated the hydraulic factors contributing to the decreasing groundwater levels across Jeju island. Time-series data for groundwater level, precipitation, and groundwater usage and information on land use were acquired, and the correlations among them were analyzed to evaluate the causes of the decreasing groundwater. The effects of precipitation and groundwater usage on the fluctuations of groundwater level were quantified using response surface analysis and sensitivity analysis, and methods for groundwater quantity management by region were proposed. The results showed that the rate of groundwater decrease in the western region was larger than that in the eastern region. For the eastern region, the influence of precipitation was large and the rate of decrease in the groundwater level was relatively small. The geological formation of this part of the island and continuous seawater intrusion suggest that although the absolute amount of groundwater extracted for use was large, the decrease in the groundwater level was not seen to be great due to an increase in pressure by seawater intrusion. Overall, precipitation and groundwater usage had the greatest effect on the amount of groundwater in the western region, and thus their data would be most useful for informing groundwater management, whereas other factors (e.g., sea level and the location of the freshwater-seawater transition zone) must be considered when understanding Jeju's eastern region. As the characteristics of groundwater level fluctuations in the eastern and western regions are distinct, an optimal management plan for each region should be proposed to ensure the efficient management of groundwater quantity.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.40 no.1
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• pp.1-14
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• 2022

This study focused on examining the location characteristics of Mujang-Eupchi(茂長邑治), a traditional city of Joseon Dynasty, and shedding light on its prototype landscape. The findings were summarized as follows: Mujang-Eupchi showed a Confucian space system with Munmyo(文廟) within Hyanggyo(鄕校) in the east, Sajikdan(社稷壇) in the west, Seonghwangsa(城隍祠) in the fortress and Yeodan(厲壇) and Seonghwangdan(城隍壇) in Jinsan(鎭山) in the north around the Mujang-Eupseong(茂長邑城), an old fortress, built in the 17th year of King Taejong(1417). It seemed that Seonghwangdan located in Jinsan maintained a coexistence system with Seonghwangsa(城隍祠) within the Eupseong. A Pungsu(風水) stream in a V-shape ran before the southern gate of Eupseong, forming a Sugu(水口) in front of Namsan(南山) that was an Ansan(案山). They dug a southern pond called Hongmunje(紅門堤) to protect the vitality of the village and built Gwanpungjeong(觀豊亭). In the 19th century, Hongmunje and Gwanpungjeong were renamed into Muheungje(茂興堤) and Muheungdang(茂興堂), respectively. Eupsu(邑藪) were planted in front of the southern pond including Wondo(圓島), and Songdeokbi(頌德碑), Dangsanmok(堂山木), and Dangsanseok(堂山石) served as a Sugumagi(水口막이) and protected the entrance of Eupchi. After the Liberation, the southern pond was buried in 1955, and a market was formed at the site, which resulted in the disappearance of its prototype. The study also investigated the name and location of Chilgeori(七거리) in the village as it was lost following the unification of Bu(府), Gun(郡), and Myeon(面) titles in 1914 during the Japanese colonial period. Chilgeori Dangsan was based on Yin and Yang theory and became the subject of the organization mainly composed of Grandfather Dangsan menhir and Grandmother Dangsan tree. Chilgeori Dangsan was a religious place of the community to guard the village, serving as seven gateways to control access at the village boundary and it had a locational feature of protecting the inner mountain ranges of Eupchi.