• Journal of Environmental Science International
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• v.13 no.6
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• pp.527-535
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• 2004

As urbanization has been expanded in Korea, open spaces, such as urban parks and public sites, have been utilized for other uses, and then this bring out environmental changes for the worse. It is expected that these changes become more serious problems due to overpopulation, increasing individualism, and development of transportation. This research base on the consideration of connecting between decreasing urban green spaces and distributed green sites so as to build the substantial plan for the Green Network construction for urban heat island mitigation in Dalseo district, Daegu Metropolitan City. The result were as follow; 1) Connecting existing natural sites to the remained parks green zone made an Ideal form of Green-Network system. 2) Some school sites were selected for usable open spaces in order to build Green-Network system, and the plan connecting together with exist natural sites was suggested. 3) Moreover, the scheme of planting on the road spaces for connecting green spaces was proposed. 4) The devices of planting on the urban riverside for enhancing the role of urban stream to form green network was conceived.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.585-594
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• 2014

This study Analyzed four of seven runoffs which had happened in 2012 in comparison with the runoffs shown in Kalesto data, using the fixed surface image velocimetry (FSIV) installed at Oedo stream, Jeju Island. As a result of identifying a runoff curve graph, it was analyzed that the flood runoffs calculated with two observation devices were almost equivalent. As the differences in peak flows were 10 $m^3/s$, 0.7 $m^3/s$ and 3 $m^3/s$, the very similar result values were calculated. Even though there were errors in RMSE(Root Mean Square Error) made by two observation devices according to the degree of the peak flow, the values of $R^2$ by flood event were 0.89, 0.87, 0.86 and 0.82, showing the result values almost close to 1. Therefore, there was a very high correlation in flood runoffs calculated with two observation devices. This research method was considered to be a very suitable method to measure unexpected flood runoffs which could happen in the island area such as Jeju island during bad weather.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.442-442
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• 2015

최근 도시 집중화 개발사업의 증가로 인해 유역의 유출환경이 크게 변화하고 있다. 특히, 도시화에 따른 불투수층 토지가 크게 증가함에 따라 지표면의 이용과 형질이 변형됨으로써 지표수 흐름과 지하수 함양 및 오염 등의 문제가 심각하게 대두되고 있는 실정이다. 제주도는 관광객 증가로 인한 각종 개발사업이 지속적으로 추진되고 있으나, 사전재해 영향성검토에서는 개발사업 소유역을 중심으로만 평가하고 있어 하천유역의 도시화에따른 홍수재해 영향은 검토하지 못하고 있는 실정이다. 따라서 본 연구에서는 제주도 도심하천인 한천유역을 대상으로 국가 수자원관리 종합시스템과 환경부에서 제공하는 1980년부터 2005년까지 5년 주기의 토지피복도를 이용하여 유역 내 토지이용 변화를 분석하고 호우사상에 따른 홍수유출 변동을 분석하여 토지이용 변화가 홍수유출량 미치는 영향을 도출하고자 한다.

• Journal of Environmental Science International
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• v.25 no.8
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• pp.1165-1176
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• 2016

The accuracy of digital elevation models (DEMs) is crucial for properly estimating flood inundation area. DEM pixel size is especially important when generating flood inundation maps of small streams with a channel width of less than 50 m. In Korea, DEMs with large spatial resolutions of 30 m have been widely applied to generate flood inundation maps, even for small streams. Additionally, when making river master plans, field observations of stream cross-sections, as well as reference points in the middle of the river, have not previously been used to enhance the DEM. In this study, it was graphically demonstrated that high-resolution DEMs can increase the accuracy of flood inundation mapping, especially for small streams. Also, a methodology was proposed to modify the existing low-resolution DEMs by adding additional survey reference points, including river cross-sections, and interpolating them into a high spatial resolution DEM using the inverse distance weighting method. For verification purposes, the modified DEM was applied to Han stream on Jeju Island. The modified DEM showed much better accuracy when describing morphological features near the stream. Moreover, the flood inundation maps were formulated with the original 30 m pixel DEM and the modified 0.1 m pixel DEM using HEC-RAS modeling of the actual flood event of Typhoon Nari, and then compared with the flood history map of Nari. The results clearly indicated that the modified DEM generated a similar inundation area, but a very poor estimate of inundation area was derived from the original low-resolution DEM.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.5 no.1
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• pp.1-10
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• 1972

Studies on the circulation and water masses in the continental shelf break region of the East China Sea are Summerized as follows : 1. The main stream of the Kuroshio flowing north-east near $29^{\circ}N\;Lat\;127^{\circ}E$ tong of the East China Sea in summer is narrow in width. Moving toward east, it becomes twice as wide in Tokora Strait, Japan. 2. In the main stream area of the Kuroshio, the surface Waters in the Upper layer (0-250m) are influenced by the coastal waters of China, and the counter current submerges under the surface water. Therefore, the mixing waters are found in its intermediate layer. 3. Water mass between Amami Island and the continental shelf of the East China Sea consists of main stream water, counter current water, gyration water and mixed water with coastal waters. 4. The maximum velocity of current in this waters was 139cm/sec. The volume transport was estimated approximately as $24.2\;\times\;10^6m^3/sec$. It was less than $33\;\times\;10^6m^3/sec$ in the region between Okinawa and continental shelf of the East China Sea. 5. Surface waters east of $29^{\circ}N\;Lat\;128^{\circ}E$ Long flows toward Amami Island, Okinawa Island, and Hachi Ju San Island, while those west of the region flow toward the Korea-strait, Cheju Island, coastal waters of Kyusyu, and the Pacific Ocean through Tokora Strait. The velocity of the current was estimated approximately as $0.3\~0.5$ miles per hour. 6. The bottom waters in the continental shelf break region flow toward the Korea Strait, Cheju Island and the coastal water of Kyusyu, while that of the continental shelf flows toward the Yellow Sea, 7, The characteristics of the Kuroshio water is changed remarkably by the mixing with the coastal water of China.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.951-959
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• 2016

This study was conducted to evaluate observed runoff data collected every 10 minutes at stream gauging stations in Jeju Island using a physically-based model, SWAT. The Hancheon watershed was selected as study area, and ephemeral stream algorithm suggested by previous research was incorporated into the model, which is able to simulate ephemeral runoff pattern of Jeju streams. Simulated runoff and runoff rates were compared to observations during 2008-2013, which showed 'very good' performance rating in Nash-Sutcliffe model efficiency (ME) and determination coefficient ($R^2$). Some observations had problems such that runoff rates were very high for some rainfall events with little amount of antecedent rainfall, and were very low or missing with much rainfall comparing to previous researches. Additionally, regression equation between precipitation and simulated runoff was generated with high degree of correlation. The equation can be utilized to simply predict reasonable runoff, or to investigate and complement the abnormal or missing data of observations on the assumption that modelling results were sufficiently reliable and satisfactory. As results, minimizing the error in calibrating the model by evaluation of observed data would be helpful to accurately model the rainfall-runoff characteristics and analyze the water balance components of watersheds in Jeju Island.

• Journal of the Korean association of regional geographers
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• v.3 no.2
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• pp.19-35
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• 1997

The purpose of this study is to find out the characteristics of landform in Geoje-Do using GIS and DTED data. The characteristics of landform in Geoje-Do are as follows; First, the height-range of Geoje-Do is $0{\sim}580m$, and the average elevation of it is 124m. Volcanic and granite region is mainly appeared at high elevation-region. But, we can't find out outstanding difference of elevation, according to its geology. The second. the slope-range of Geoje-Do is $0{\sim}52$ degree, and the average slope of it is 17.6 degree. The slope of volcanic and granite area is more steeper than any other region. But the results of analysis of the geology in Geojo-Do, don't show outstanding difference of the slope. The third, the area-rate of the aspect of Geoje-Do is almost same in all direction. And the area-rate of south-west direction is the highest. According to the geology of Geoje-Do, granite is distributed the most widely, and the area of volcanic and granite occupy 60% of entire island's area. According to analysis of influence of geology with elevation, geology has little relationship with elevation. According to analysis of geology and drainage network, streams are inclined to be developed well in Alluvium area. Drainage network is well developed throughout the entire island, except southeast area. The highest order of stream is 4 in 1:25,000 topographic map. The density of stream in Geoje-Do is very high, such as 1.6. The bifurcation-ratio of stream is also higher than 4 in all order. The length-ratio of stream is ranged from 1.24 to 3.25. According to the relationship between order and elevation. order is the greater, elevation is the lower. According to the relationship between order and slope, order is the greater, slope is the gentler. In this study, we use DTED Data, and compare it with topographic map data. According to the comparison, there is a little difference between DTED data and topographic map data. Therefore, to use DTED data in landform analysis, it is required coordinate matching process. This process is very important, and take very long time. Thus, if you use DTED in landform analysis, some processes are required. DTED data can be taken very easily, but its using is not simple. Because coordinate adjust is very hard work.

• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.361-372
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• 2016

Lahar, one of catastrophic events, has the potential to cause the loss of life and damage to infrastructure over inhabited areas. This study using Laharz_py program, was performed schematic prediction on the impact area of lahar hazards at the Mt. Halla volcano, Jeju island. In order to comprehensively address the impact of lahar for the Mt. Halla, two distinct parameters, H/L ratio and lahar volume, were selected to influence variable for Laharz_py simulation. It was carried out on the basis of numerical simulation by estimating a possible lahar volumes of 30,000, 50,000, 70,000, 100,000, 300,000, $500,000m^3$ according to H/L ratios (0.20, 0.22 and 0.25) was applied. Based on the numerical simulations, the area of the proximal hazard zone boundary is gradually decreased with increasing H/L ratio. The number of streams which affected by lahar tended to decrease with increasing H/L ratio. In the case of H/L ratio 0.20, three streams (Gwangryeong stream, Dogeun stream, Han stream) in the Jeju-si area and six streams (Gungsan stream, Hogeun stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. In the case of H/L ratio 0.22, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and five streams (Gungsan stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. And in the case of H/L ratio 0.25, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and one stream (Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. The results of this study will be used as basic data to create a risk map for the direct damage that can be caused due to volcanic hazards arising from Mt. Halla.

• Journal of Environmental Science International
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• v.24 no.4
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• pp.371-381
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• 2015

In the mountain streams in Jeju Island, strong turbulence and roughness usually made it nearly impossible to utilize most of intrusive instrumentation for streamflow discharge measurements. Instead, a non-intrusive fixed electro-magnetic wave surface velocimetry (fixed EWSV: Kalesto) became alternatively popular in many representative streams to measure stream discharge seamlessly. Currently, Kalesto has shown noteworthy performance with little loss in flood discharge measurements and also has successfully provided discharge for every minute. However, Kalesto has been operated to regard its measured one-point velocity as the representative mean velocity for the given cross-section. Therefore, it could be highly possible to potentially encompass discharge measurements errors. In this study, we analyzed the difference between such Kalesto discharge measurements and other alternative concurrent discharge measurements such as Acoustic Doppler Current Profiler (ADCP) and mobile EWSV which were able to measure velocity in multi-points in the cross-section. Consequently, Kalesto discharge deviated from ADCP discharge in amount of 48% for relatively low flow, and more than 20% difference for high flow compared with mobile EWSV discharge measurements. These results indicated that the one-point velocity measured by Kalesto should be used as a cross-sectional mean velocity, rather it should be accounted for as an index-velocity in conjunction with directly measured cross-sectional mean velocity by using more reliable instrumentations. After inducing Kalesto Discharge Correction Coefficient (KDCC) that actually means relationship between index velocity and cross-sectional mean velocity, the corrected discharge from Kalesto was significantly improved. Therefore, we found that index velocity method should be applied to obtain better accuracy of discharge measurement in case of Kalesto operation.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.561-569
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• 2014

The water resources system of Jeju-do Island entirely depends on groundwater. This study is making a precision observation of baseflow, surface water, water shortage that might be vulnerable to climate change and drought in future. The field observation of baseflow discharges in Akgeuncheon stream has regularly been made with ADCP and ADC and Flowmate every two weeks for twenty-two (22) months (July 8, 2011 to April 27, 2013). This paper represent the results of calculating discharge of a number of hydraulic structures (broad-crested weirs) with comparing and has been calculated more accurate discharges with suitability of different observation methods. The average discharge has been observed 0.851 $m^3/s$, whereas the average ADC and Flowmate is 0.709 $m^3/s$. Meanwhile, stream discharge has been calculated 0.709 $m^3/s$ through the broad-crested weir equation. The discharge has calculated with the weir equation greatly changed according to even a small change in the water level. However, it showed a similar trend to one of the observed discharge. Although, in past there were generating errors caused by observers' strides, vertical and horizontal flow velocity distribution when the average flow velocity had been measured, non-prismatic flow, turbulent flow and others in ADC. This study comes up with the weir equation is more suitable for the characteristics of Jeju-do could be presented through an observations of baseflow discharge.