• Ocean and Polar Research
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• 제42권2호
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• pp.115-131
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• 2020

The effective range of surface current data observed by high-frequency radar (HFR) operated in the northern coastal area of Jeju Island by Korea Institute of Ocean Science and Technology was estimated and the distribution and variability of the M₂ tidal current of the Jeju Strait was analyzed. To evaluate the HFR data, the M₂ tidal current corrected from 25 hours current data observed by the Korea Hydrographic and Oceanographic Agency (KHOA) was compared with the M₂ tidal current in the Jeju Strait analyzed from the surface currents of HFR. The reliability of HFR data was confirmed by analyzing the characteristics of the tide components of these two data sets, and the effective range of HFR data was estimated through temporal and spatial analysis. The observation periods of HFR used in the analysis were from 2012 to 2014, and it was confirmed that there is a difference in the effective range of HFR data according to the observation time. During the analysis periods, the difference between the M₂ current ellipses from the data of KHOA and the HFR was greater in the eastern than in the western part of the Jeju Strait, and represented a high reliability in the western and central parts of the Jeju Strait. The tidal current of the Jeju Strait analyzed using the HFR data revealed a seasonal variability a relatively weak in summer and a strong in winter, about a 17% fluctuations between the summer and winter based on the length of the semi-major axis of tidal ellipse. Appraisals and results of regarding the characteristics and seasonal variability of the M₂ tidal current in the Jeju Strait using HFR data have not been previously reported, so the results of this study are considered meaningful.

• Ocean and Polar Research
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• 제43권4호
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• pp.205-217
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• 2021

A shallow channel between Jeju and Udo Islands, which is located in the northeastern Jeju Island, is influenced by storm- or typhoon-induced currents and surface waves as well as strong tidal currents. This study examines the typhoon-induced current and wave patterns in the channel, using Acoustic Doppler Current Meter (ADCP) measurements and an ocean-wave coupled modeling experiment. Three typhoons were chosen - Chaba (2016), Soulik (2018), and Lingling (2019) - to investigate the responses of currents and waves in their pathways. During the pre-typhoon periods, dominant northward flow and wave propagation were observed in the channel due to the southeasterly winds before the three typhoons. After the passage of Chaba, which passed over the eastern side of Jeju Island, the northward flow and wave propagation were totally reversed to the opposite direction, which was attributed to the strong northerly winds on the left side of the typhoon. In contrast, in the cases of Soulik and Lingling, which passed over the western side of Jeju Island, strong southerly winds on the right side of the typhoons continuously intensified the northward current and wave propagation in the channel. The model-simulated current and wave fields reasonably coincided with observational data, showing southward/northward flow and wave propagation in response to the right/left side of the typhoon pathways. Typhoon-induced downwind flows, and surface waves could enhance up to 2m/s and 3m due to the strong winds that lasted for more than 12 hours. This suggests that the flow and wave patterns in the Udo channel are highly sensitive to the pathway of typhoons and accompanying winds; thus, this may be a crucial factor with regard to the movement of seabed sediments and subsequent coastal erosion.

• Ocean and Polar Research
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• 제43권4호
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• pp.307-320
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• 2021

Udo Rhodolith Beach is a small-scale, mixed sand-and-gravel beach embayed on the N-S trending rocky coast of Udo, Jeju Island, South Korea. This study analyzes the short-term topographic changes of the beach during the extreme storm conditions of four typhoons from 2016 to 2020: Chaba (2016), Soulik (2018), Lingling (2019), and Maysak (2020). The analysis uses the topographic data of terrestrial LiDAR scanning and drone photogrammetry, aided by weather and oceanographic datasets of wind, wave, current and tide. The analysis suggests two contrasting features of alongshore topographic change depending on the typhoon pathway, although the intensity and duration of the storm conditions differed in each case. During the Soulik and Lingling events, which moved northward following the western sea of the Jeju Island, the northern part of the beach accreted while the southern part eroded. In contrast, the Chaba and Maysak events passed over the eastern sea of Jeju Island. The central part of the beach was then significantly eroded while sediments accumulated mainly at the northern and southern ends of the beach. Based on the wave and current measurements in the nearshore zone and computer simulations of the wave field, it was inferred that the observed topographic change of the beach after the storm events is related to the directions of the wind-driven current and wave propagation in the nearshore zone. The dominant direction of water movement was southeastward and northeastward when the typhoon pathway lay to the east or west of Jeju Island, respectively. As these enhanced waves and currents approached obliquely to the N-S trending coastline, the beach sediments were reworked and transported southward or northward mainly by longshore currents, which likely acts as a major control mechanism regarding alongshore topographic change with respect to Udo Rhodolith Beach. In contrast to the topographic change, the subaerial volume of the beach overall increased after all storms except for Maysak. The volume increase was attributed to the enhanced transport of onshore sediment under the combined effect of storm-induced long periodic waves and a strong residual component of the near-bottom current. In the Maysak event, the raised sea level during the spring tide probably enhanced the backshore erosion by storm waves, eventually causing sediment loss to the inland area.

• 토지주택연구
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• 제12권4호
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• pp.81-92
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• 2021

본 연구는 도시확장이 원도심 쇠퇴의 원인으로 작용할 수 있을 것으로 가정하고, 그 가능성을 공간구문론(Space Syntax) 방법론으로 검토하고자 제주읍성 일대의 원도심을 대상으로 도시공간구조 분석을 수행하였다. 도시공간구조에 관한 종단적 분석의 시점은 일제강점기부터 현재 사이에 1914년, 1972년, 1982년, 1996년, 그리고 2021년 현재의 5개 시점으로 설정하였다. 도시공간구조 분석은 공간구문론의 ASA(Angular Segment Analysis)를 활용하였다. 분석결과, 제주시 동지역의 도시구조는 1914년에서 2021년 사이에 큰 변화를 겪어왔다. 도심은 단일핵 구조에서 다핵 구조로 변화하였으며, 원도심이 위치한 구제주 지역은 지리적으로 바다와 접하여, 도시확장이 한라산 자락의 남측으로 편중되어 도시중심부의 위치도 점차 남쪽으로 이동하였다. 이에 따라 제주시 원도심은 도시공간구조의 역동성에 의하여 도시중심부의 중심지에서 주변지역의 하나로 전락하였다. 이와 같이, 도시확장에 의한 도시공간구조 변화 과정에서 원도심의 도시중심부 이탈이 이루어졌다는 점에서, 원도심 쇠퇴의 한 요인으로서 도시확장의 가능성을 확인할 수 있었다.

• 한국지리정보학회지
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• 제27권2호
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• pp.45-60
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• 2024

본 연구는 제주지역에서 발생한 관광객 안전사고 발생현황을 GIS를 통하여 분석하고 이를 통하여 제주지역 관광객 안전사고에 대한 이해의 폭을 넓히는 것을 목적으로 한다. 제주도 동부 읍면지역이 연구대상지로 선택되었으며 2021년도가 연구기간으로 설정되었다. 분석에는 2021년 1년간 제주지역에서 발생한 관광객 안전사고 데이터와 안전사고 발생에 따른 구급출동 데이터가 활용되었다. 안전사고 발생현황 데이터를 바탕으로 제주 전지역에 대한 관광객 안전사고 발생 현황에 대한 분석을 우선적으로 실시하였으며, 그 결과 월별, 시간별, 장소별 관광객 안전사고의 발생 패턴을 확인하였다. 이어서 공간데이터를 바탕으로 격자분석과 중첩분석을 활용하여 관광객 안전사고와 구급출동 현황을 분석하여 관광객 안전사고 취약지역을 도출하였다. 본 연구는 이러한 관광객 안전사고에 대한 GIS 분석을 통하여 관광객의 활동 특성을 고려한 안전사고 예방 및 대응 대책의 필요성을 제시하였으며, 특히 취약지역에 대한 관광시설물 점검과 안전사고 예방 홍보 활동과 같은 적극적인 예방조치가 필요함을 제시하였다.

• 대한지리학회지
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• 제49권1호
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• pp.18-31
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• 2014

이 연구에서는 제주도 지역에서 태풍에 의해 야기되는 조풍(潮風) 발생 및 식생에 나타난 피해의 시 공간적 특징을 밝히고자 하였다. 이를 위해 2012년 8월 하순 제주도를 강타한 태풍 볼라벤(BOLAVEN)의 통과시 기상자료를 분석하고 이후 야외답사를 수행하여 제주도 식생에 나타난 조풍해 정도를 조사하였다. 그 결과, 조풍해는 주로 제주도 남부 및 동부 해안지역에서 발생한 것으로 나타났으며, 태풍이 동반한 강한 남동풍과 상대적으로 적은 강수량이 그 원인으로 분석되었다. 조풍에 의해 해안에서 약 8km 범위 내의 삼나무(Cryptomeria japonica)와 해안지역의 곰솔(Pinus thunbergii)을 포함한 대부분의 식생이 피해를 입었으나, 그 피해정도 및 회복력은 수종별로 차이가 있었다. 조풍에 의한 식생 피해를 줄이기 위해서는 강풍성 마른 태풍이 접근 시 조풍해 발생을 예측하고 방제대책을 마련하는 것이 필요하다.

• 한국환경과학회지
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• 제22권5호
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• pp.639-649
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• 2013

Over 96.2% of the agricultural water in Jeju Island is obtained from groundwater and there are quite distinct characteristics of agricultural water demand/supply spatially because of regional and seasonal differences in cropping system and rainfall amount. Land use for cultivating crops is expected to decrease 7.4% (4,215 ha) in 2020 compared to 2010, while market garden including various vegetable crop types having high water demand is increasing over the Island, especially western area having lower rainfall amount compared to southern area. On the other hand, land use for fruit including citrus and mandarin having low water demand is widely distributed over southern and northern part having higher rainfall amount. The agricultural water demand of $1,214{\times}10^3\;m^3/day$ in 2020 is estimated about 1.39 times compared to groundwater supply capacity of $874{\times}10^3\;m^3/day$ in 2010 with 42.4% of eastern, 103.1% of western, 61.9% of southern, and 77.0% of northern region. Moreover, net secured amount of agricultural groundwater would be expected to be much smaller due to regional disparity of water demand/supply, the lack of linkage system between the agricultural water supply facilities, and high percentage of private wells. Therefore, it is necessary to ensure the total net secured amount of agricultural groundwater to overcome the expected regional discrepancy of water demand and supply by establishing policy alternative of regional water supply plan over the Island, including linkage system between wells, water tank enlargement, private wells maintenance and public wells development, and continuous enlargement of rainwater utilization facilities.

• 한국수산과학회지
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• 제45권6호
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• pp.704-715
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• 2012

To examine temporal and spatial variation in salinity and nutrients in the shallow pore water of intertidal sandflats, we measured salinity and nutrient concentrations (dissolved inorganic nitrogen [DIN], phosphorus [DIP], and silicate [DSi]) in pore water of the intertidal zone along the coastline of Jeju Island at two and/or three month intervals from May 2009 to December 2010. Geochemical parameters (grain size, ignition loss [IL], chemical oxygen demand [COD], and acid volatile sulfur [AVS]) in sediment were also investigated. The surface sediments in intertidal sandflats of Jeju Island were mainly composed of sand, slightly gravelly sand and gravelly sand, with a range of mean grain size from 0.5 to 2.5 ${\O}$. Concentrations of IL and COD in sediment were higher along the eastern coast, as compared to the western coast, due to differences in biogenic sediment composition. Salinity and nutrient concentrations in pore water were markedly different across time and space during rainy seasons, whereas concentrations were temporally and spatially more stable during dry seasons. These results suggest that salinity and nutrient concentrations in pore water depend on the advective flow of fresh groundwater. We also observed an imbalance of the DIN/DIP ratio in pore water due to the influence of contaminated sources of DIN. In particular, nutrient concentrations during rainy and dry seasons were characterized by high DIN/DIP ratios (mean-127) and low DIN/DIP ratios (mean-10), respectively, relative to the Redfield ratio (16) in offshore seawater. Such an imbalance of DIN/DIP ratios in pore water can affect the coastal ecosystem and appears to cause outbreaks of benthic seaweed along the coastline of Jeju Island.

• 한국환경과학회지
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• 제23권4호
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• pp.661-672
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• 2014

Due to tidal force, it is very difficult to estimate the hydraulic parameters of high permeable aquifer near coastal area in Jeju Island. Therefore, to eliminate the impact of tidal force from groundwater level and estimate the hydraulic properties, tidal response technique has been mainly studied. In this study we have extracted 38 tidal constituents from groundwater level and harmonic constants including frequency, amplitude, and phase of each constituent using T_TIDE subroutine which is used to estimate oceanic tidal constituents, and then we have estimated hydraulic diffusivity associated with amplitude attenuation factor(that is the ratio of groundwater level amplitude to sea level amplitude for each tidal constituent) and phase lag(that is phase difference between groundwater level and sea level for each constituent). Also using harmonic constants for each constituent, we made the sinusoidal wave and then we constructed the synthesized wave which linearly combined sinusoidal wave. Finally, we could get residuals(net groundwater level) which was excluded most of tidal influences by eliminating synthesized wave from raw groundwater level. As a result of comparing statistics for synthesized level and net groundwater level, we found that the statistics for net groundwater level was more insignificant than those of synthesized wave. Moreover, in case of coastal aquifer which the impact of tidal force is even more than those of other environmental factors such as rainfall and groundwater yield, it is possible to predict groundwater level using synthesized wave and regression analysis of residuals.

• 한국환경과학회지
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• 제23권4호
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• pp.637-647
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• 2014

Quantitative assessment of groundwater level change under extreme event is important since groundwater system is directly affected by drought. Substantially, groundwater level fluctuation reveals to be delayed from several hours to few months after raining according to the aquifer characteristics. Groundwater system in Jeju Island would be also affected by drought and almost all regions were suffered from a severe drought during summer season (July to September) in 2013. To estimate the effect of precipitation to groundwater system, monthly mean groundwater levels in 2013 compared to those in the past from 48 monitoring wells belong to be largely affected by rainfall(Dr) over Jeju Island were analyzed. Mean groundwater levels during summer season recorded 100 mm lowered of precipitation compared to the past 30 years became decreased to range from 2.63 m to 5.42 m in southern region compared to the past and continued to December. These decreasing trends are also found in western(from -1.21 m to -4.06 m), eastern(-0.91 m to -3.24 m), and northern region(from 0.58 m to -4.02 m), respectively. Moreover, the response of groundwater level from drought turned out to be -3.80 m in August after delaying about one month. Therefore, severe drought in 2013 played an important role on groundwater system in Jeju Island and the effect of drought for groundwater level fluctuation was higher in southern region than other ones according to the regional difference of precipitation decrease.