황세운 Hwang Syewoon , 아세파터루소 Asefa Tirusew , 장승우 Chang Seungwoo

DOI: JKWST Vol.55(No.6) 1-9, 2013

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조일호 Cho Il Ho , 성찬용 Sung Chan Yong

DOI: JKWST Vol.55(No.6) 11-17, 2013

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This study was performed to evaluate the chlorine ion penetration resistance, chemical resistance and freezing and thawing resistance used ordinary portland cement, crushed coarse aggregate, crushed sand, river sand, fly ash, limestone powder, blast furance slag powder and superplasticizer to find optimum mix design of low carbon green concrete for structures. The performance of low carbon green concrete used fly ash, limestone powder and blast furnace slag powder were remarkably improved. This fact is expected to have economical effects in the manufacture of low carbon green concrete for offshore structures. Accordingly, the fly ash, limestone powder and blast furnace slag powder can be used for offshore structure materials.

안소라 Ahn So Ra , 장철희 Jang Cheol Hee , 김상호 Kim Sang Ho , 한명선 Han Myoung Sun , 김진훈 Kim Jin Hoon , 김성준 Kim Seong Joon

DOI: JKWST Vol.55(No.6) 19-30, 2013

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This study is to evaluate the use of dual-polarization radar data for storm runoff modeling in Namgang dam (2,293 km²) watershed using KIMSTORM (Grid-based KIneMatic wave STOrm Runoff Model). The Bisl dual-polarization radar data for 3 typhoons (Khanun, Bolaven, Sanba) and 1 heavy rain event in 2012 were obtained from Han River Flood Control Office. Even the radar data were overall less than the ground data in areal average, the spatio-temporal pattern between the two data was good showing the coefficient of determination (R²) and bias with 0.97 and 0.84 respectively. For the case of heavy rain, the radar data caught the rain passing through the ground stations. The KIMSTORM was set to 500×500 m resolution and a total of 21,372 cells (156 rows×137 columns) for the watershed. Using 28 ground rainfall data, the model was calibrated using discharge data at 5 stations with R², Nash and Sutcliffe Model Efficiency (ME) and Volume Conservation Index (VCI) with 0.85, 0.78 and 1.09 respectively. The calibration results by radar rainfall showed R², ME and VCI were 0.85, 0.79, and 1.04 respectively. The VCI by radar data was enhanced by 5 %.

염성현 Yum Sung Hyun , 강승희 Kang Seung-hee

DOI: JKWST Vol.55(No.6) 31-35, 2013

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This study was carried out to present the pressure drop for various wind speeds through nine types of screens used in horticultural facilities. The screens have been widely used to prevent harmful insects from being entered into agricultural facilities, to reduce strong wind and to shade a light as well. Whatever the usage of the screens was, it was necessary to have good knowledge of how much the screen caused a pressure drop for wind speeds when analyzing both the inner thermal-flow distribution in the facility and the effect of reducing wind speed by using CFD. Furthermore, as for wind screens, the pressure drop for wind speeds was needed as a design load in evaluating the structural stability of the structures supporting the screens. Therefore, the pressure drop through the screens for wind speeds of 5～30 m · s^-1 at about 5 m · s^-1 interval and inflow angles of 0∼45° at an interval of 15° was respectively measured in a subsonic wind tunnel. The relation of the pressure drop for various screens was well fitted as a secondorder polynomial expression.

노수각 Noh Soo-kack , 손영환 Son Young-hwan , 봉태호 Bong Tae-ho , 박재성 Park Jae-sung , 최우석 Choi Woo-seok

DOI: JKWST Vol.55(No.6) 37-46, 2013

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Many factors about the stability for the reservoir embankments is determined when the facility is completed. Therefore the initial design of the embankment is important. Many researchers focused the effect of soil parameters although the cross section greatly affects the stability and can be controlled in design step. The objective of this research is to analysis of the effects for the safety factor of slope and seepage according to change cross-section in embankment. As a result, the quantity of seepage decreased as the gradient of downstream slope decreased and was proportional to the height of embankments. There was a linear relationship between the gradient of slope and the safety factor of slope. However the gradient of slope did not affect other side slope. All in a relationship, regressive equations with a high correlation coefficient were calculated and can be applied the simple estimation method of the stability using the cross-section. As results of analyzing the sensitivity, the friction angle and permeability critically effect for the slope stability and the seepage, respectively. The effect of the slope gradient was similar to major soil properties.

박진기 Park Jin Ki , 김봉섭 Kim Bong Seop , 오시영 Oh Si Young , 박종화 Park Jong Hwa

DOI: JKWST Vol.55(No.6) 47-55, 2013

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The objective of this study is to evaluate the applicability of Communication, Ocean, and Meteorological Satellite (COMS) Geostationary Ocean Color Imager (GOCI) vegetation indices on a quantitative analysis. For evaluation, the vegetation indices such as RVI, NDVI and SAVI were extracted by using COMS GOCI and Terra Moderate Resolution Imaging Spectroradiometer (MODIS) imageries. The 4,000 points using simple random sampling (SRS) method were randomly extracted from land areas except ocean to compare the vegetation indices from two images. The results of linear regression showed that the regression coefficients of RVI, NDVI, and SAVI between COMS GOCI and Terra MODIS were 0.66～0.82, 0.71～0.83, and 0.71～0.83, respectively. Especially, the regression coefficients of RVI (r＝0.85), NDVI (r＝0.91) and SAVI (r＝0.91) were strongly related from September 2011 to January 2012. Thus, COMS GOCI can be substituted for particular periods and it needs to verify additionally.

전상민 Jun Sang Min , 강문성 Kang Moon Seong , 송인홍 Song Inhong , 황순호 Hwang Soon Ho , 김계웅 Kim Kyeung , 박지훈 Park Jihoon

DOI: JKWST Vol.55(No.6) 57-68, 2013

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About 74 % of reservoirs in Korea are older than 40 years and their storage capacities have been decreased substantially. As part of reservoir reinforcement, the dam heightening project has been ongoing for about 110 reservoirs. The main purpose of the dam heightening project is to secure additional environmental water, while improving flood control capacity by gaining additional storage volume. The objective of this study was to evaluate reservoir flood control capacity changes of dam heightening reservoirs for effective management of additional storage volume. In this study, 13 reservoirs were selected for reservoir simulation of 200 year return period floods. Rainfall data of 1981-2100 were collected and divided into 4 periods (1981-2010; 1995s, 2011-2040; 2025s, 2041-2070; 2055s, 2071-2100; 2085s). Probability rainfalls and 200yr design floods of each period were calculated using FARD2006 and HEC-HMS. Design floods were used as inputs of each reservoir simulation using HEC-5. Overall, future probability rainfalls and design floods tend to increase above the past 1995s. Control ratios were calculated to evaluate flood control capacities of reservoirs. As a result, average flood control ratios were increased from 32.6 % to 44.2 % after dam heightening. Control ratios were increased by 12.7 % (1995s), 12.4 % (2025s), 10.3 % (2055s) and 10.9 % (2085s). The result of this study can be used as a basis for establishing the reservoir management structure in the future.

강구 Kang Ku , 홍성구 Hong Seong-gu , 박성직 Park Seong-jik

DOI: JKWST Vol.55(No.6) 69-75, 2013

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Miscanthus has received wide attention as an option for biomass production in Korea, recently. New strain of giant miscanthus has been developed and was planted in two large trial sites (184 ha) in the lower reaches of the Geum River. To evaluate the susceptibility of the giant miscanthus as an bioenergy crop for the future, we investigated the influence of the giant miscanthus on the soil properties. The particle size, CEC, pH, EC, T-N, T-P, heavy metal total concentration, and heavy metal fractions of soil samples collected from abandoned field, 1 year old giant miscanthus field (1st Year GM), and 2 year old giant miscanthus field (2nd Year GM) at different depths of 0～15, 15～30, and 30～45 cm in April and August were analyzed. Results showed that the CEC and pH of the soil of the giant miscanthus field were lower than those of the soil of abandoned field. The EC of 2nd GM was lower than that of abandoned field, indicating that the giant miscanthus may facilitate soil desalination process. The organic and sulfide fraction and residual fraction of heavy metals in the giant miscanthus field was higher than in abandoned field, due to the low pH of the giant miscanthus field and the excretion of phytosiderophores by rhizome of the giant miscanthus. This study showed that the giant miscanthus can influence on the soil properties and further study for long term is needed to elucidate the interaction between the soil and the giant miscanthus.

남원호 Nam Won Ho , 최진용 Choi Jin Yong

DOI: JKWST Vol.55(No.6) 77-85, 2013

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The efficient operation and management strategies of reservoirs in irrigation periods of drought events are an essential element for drought planning and countermeasure. Korea Rural Community Corporation has developed the real-time water level observation system of agricultural reservoirs to efficiently operate reservoirs, however, it is not possible to predict drought conditions, and only provides information of current situation. Hence, it is necessary to evaluate accurate irrigation vulnerability and efficiently reservoir operation rules using current water level. In this paper, the improvement methods of reservoir operation planning were developed with water supply vulnerability characteristic curves comparing to automatic water gauge at agricultural reservoirs. The 11 reservoirs were simulated applying the reservoir operation rules which was determined by irrigation vulnerability characteristic curves criteria and real time water level, and evaluated water supply situation in 2012 year. The analysis of results can be identified probabilistic possibility of water supply failures compared with the existing reservoir operation criteria. These results of efficient reservoir operation rules can be achieved enable irrigation planners to optimally manage available water resources for decision making, and contributed to maintain the water supply according to demand strategy for agricultural reservoirs management.

주진환 Joo Jin-hwan , 정남수 Jung Nam-su , 서명철 Seo Myung-chul

DOI: JKWST Vol.55(No.6) 87-99, 2013

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For analysis of climate change effects on agriculture, precise agricultural meteorological data are needed to target period and site. In this study, agricultural meteorological data under new climate change scenario (RCP 8.5) are constructed from 2011 to 2099 in 111 agriculture major station suggested by Rural Development Administration (RDA). For verifying constructed data, comparison with field survey data in Suwon shows same trend in maximum temperature, minimum temperature, average temperature, and precipitation in 2011. Also comparison with normals of daily data in 2025, 2055, and 2085 shows reliability of constructed data. In analysis of constructed data, we can calculate sum of days over temperature and under temperature. Results effectively show the change of average temperature in each region and odd days of precipitation which means flood and dry days in target region.

허용구 Her Younggu , 유승환 Yoo Seung-hwan

DOI: JKWST Vol.55(No.6) 101-112, 2013

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Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) offers opportunities to make advances in many research areas including hydrology by providing near-global scale elevation measurements at a uniform resolution. Its wide coverage and complimentary online access especially benefits researchers requiring topographic information of hard-to-access areas. However, SRTM DEM also contains inherent errors, which are subject to propagation with its manipulation into analysis outputs. Sensitivity of hydrologic analysis to the errors has not been fully understood yet. This study investigated their impact on estimation of hydrologic derivatives such as slope, stream network, and watershed boundary using Monte Carlo simulation and spatial moving average techniques. Different amount of the errors and their spatial auto-correlation structure were considered in the study. Two sub-watersheds of Geum and Deadong River areas located in South and North Korea, respectively, were selected as the study areas. The results demonstrated that the spatial presentations of stream networks and watershed boundaries and their length and area estimations could be greatly affected by the SRTM DEM errors, in particular relatively flat areas. In the Deadong River area, artifacts of the SRTM DEM created sinks even after the filling process and then closed drainage basin and short stream lines, which are not the case in the reality. These findings provided an evidence that SRTM DEM alone may not enough to accurately figure out the hydrologic feature of a watershed, suggesting need of local knowledge and complementary data.

홍성구 Hong Seong Gu , 박성직 Park Seong Jik , 강구 Kang Ku

DOI: JKWST Vol.55(No.6) 113-120, 2013

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Miscanthus is one of the promising energy crops for producing bioethanol or bioenergy in many countries. A field of about 180 ha for miscanthus plantation was started for demonstration near Geum River in 2011. Since the size of the field is much larger than those of traditional cultivation for one single crop in this country, questions were raised if there are any environmental impacts from the energy crop plantation, particularly on water quality. In this study, water quality of runoff water from three different plots was analyzed for assessing the impacts of energy crop production. The results showed that there were no substantial differences among the plots; control, the first, and the second year growth fields. The concentrations of COD, T-N, and T-P were lower than those in runoff water from agricultural crop fields. The second year field showed a slight higher values of COD and T-N concentrations due to the biodegradation of residue of miscanthus which was not cultivated for observation. Commercial planation of miscanthus in a large scale would not result in a water quality problem when avoiding application of fertilizer as practiced in agricultural crop fields.

김형권 Kim Hyung-kweon , 전종길 Jeon Jong-gil , 백이 Paek Yee , 이상호 Lee Sang-ho , 윤남규 Yun Nam-kyu , 유주열 Yoo Ju-yeol

DOI: JKWST Vol.55(No.6) 121-125, 2013

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This study was carried out to provide a valuable reference which could reduce heating loss of air-inflated double PO film. Therefore, this study was aimed to choose the best air space thickness and injected air temperature. The characteristics of heat transmission variation at experimental materials were measured and analysed in the laboratory. The experiment was conducted of two layers of PO film, each 0.15 mm tick, sandwiching 110, 175, 225 mm of inflated air with 1 m sides. Environmental control lab was constantly controlled with －10 ℃ and experiment chamber was constantly changed with 0, 5, 10, 15 ℃. The analysis of heat transfer showed that heat transmission does not have a direct correlation with Air Space thickness and injected air temperature. But when inside and outside temperature difference of chamber was great, supply of outside air to Air Space had an advantage at reduction of heating load. It was required to examine accurate analysis at a real greenhouse.

김태완 Kim Tae-wan , 손영환 Son Young-hwan , 민슬기 Min Seul-gi , 이인복 Lee In-bok , 홍세운 Hong Se-woon , 김민영 Kim Min Young

DOI: JKWST Vol.55(No.6) 127-133, 2013

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The purpose of this study was to investigate maximum and minimum grain size which eroded by wind according to soil and wind conditions, such as top soil water content, roughness, land slope, wind velocity and proportion of grain size under 0.84mm. For performing this study, portable wind erosion tunnel was designed and utilized during field test, which facilitated measuring actual wind erosions under artificially controlled wind conditions. In the result, maximum, minimum grain size had strong negative correlation with roughness while weak positive correlation with wind velocity. Also, Slope which means the effect of gravity also influence grain size erodible by winds. Based on these results, regression equations were suggested for predicting maximum and minimum grain sizes by using multiple linear regression analysis from SPSS 20.0. The equation for maximum grain size erodible by winds showed a good agreement with the observed data with R²＝0.896. Other equation for minimum grain size had R²＝0.777.

박세준 Park Se-jun , 이인복 Lee In-bok , 홍세운 Hong Se-woon , 권경석 Kwon Kyeong-seok , 하태환 Ha Tae-hwan , 윤남규 Yun Nam-gyu , 김형권 Kim Hyung-gewon , 권순홍 Kwon Sun-hong

DOI: JKWST Vol.55(No.6) 135-144, 2013

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Ventilation efficiency has an important role in agricultural facilities such as greenhouse and livestock house to keep internally optimum environmental condition. Age-of-air concept allows to assess the ventilation efficiency of an agricultural facility according to estimating the ability of fresh air supply and contaminants emission using LMA and LMR. Most of these methods use a tracer gas method which has some limitations in experiment like dealing unstable and invisible gas. Therefore, the aim of this study was to develop a straightforward method to calculate age-of-air values with CFD simulation which has the advantage of saving computational time and resources and these method can solve the limitations in experiment using tracer gas method. The main idea of LMA computation is to solve the passive scalar transport equation with the assumption that the production of the time scalar throughout the room is uniform. In case of LMR calculation, the transport of the time scalar was reversed compulsively using UDF. The methodology to validate the results of this study was established by comparing with preceding research that had performed a computing LMA and LMR value by laboratory experiments and CFD simulations using tracer gas. As a result, the error was presented similarly level of results of preceding research. Some big errors could be caused by stagnated area and incongruity turbulence model. while the computational time was reduced to almost one fourth of that by preceding research.

김락우 Kim Rack-woo , 이인복 Lee In-bok , 홍세운 Hong Se-woon , 황현섭 Hwang Hyun-seob , 손영환 Son Young-hwan , 김태완 Kim Tae-wan , 김민영 Kim Min-young , 송인홍 Song Inhong

DOI: JKWST Vol.55(No.6) 145-154, 2013

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Recently, damage occurrence by wind erosion has been increasing in society. In times past, such problems only took place in desert area ; however, in recent years, the wind erosion problem is spreading out to agricultural land. Wind erosion in agricultural land can cause loss of loam soils, the disturbance of the photosynthesis of the crop fields and serious economic losses. To overcome the mentioned problems, installation of windbreak fence can be recommended which function as disturbing strong wind and wind erosion. However, there is still no proper guideline to install the windbreak fence and the installation used to rely on the intuition of the workers due to the lack of related studies. Therefore, this study measured the aerodynamic resistance of screens of the windbreak fence using the apparatus for testing screens. The apparatus for testing screens was designed to measure pressure loss around the screen. Measured pressure loss by wall friction compensated for pressure loss to calculate the aerodynamic resistance of screens. The result of pressure loss by regression analysis derived the aerodynamic coefficient of Darcy-Forchheimer equation and power law equation. The aerodynamic resistance was constant regardless of the overlapped shape when the screen was overlapped into several layers. Increasing the number of layers of the screen, internal resistance increased significantly more, and pressure loss caused by the screen also increased linearly when the wind speed was certain conditions, but permeability had no tendency. In the future, the results of this study will be applied to the computational fluid dynamics simulation. The simulation models will be also validated in advance by wind tunnel experiments. It will provide standard of a design for constructing windbreak fence.

박종건 Park Jong Gun , 고정희 Ko Jeong Hee , 박태섭 Park Tae Seup

DOI: JKWST Vol.55(No.6) 155-165, 2013

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Recently, geotextile tube method can be widely applied to the river, costal and marine in the construction field, such as embankment, groin, breakwater, dyke structures and so on, in advanced countries of the world. And that has been constructed at the temporary road for incheon, ilsan-bridge construction and coast erosion protection in republic of korea. Geotextile tube is a tube shaped geotextile product and hydraulic pumping filled with dredged soils. In this paper, the numerical analysis was performed to investigate the behavior of geotextile tube with various properties of material character, shape condition, construction pressure and so on. Also, the field test was conducted in order to identify the construction ability of Samangum waterproof embankment using geotextile tube. According to the applied of field test, geotextile tube was 65 m long and 4.0 m diameter. Also, the permeability coefficient and ultimate tensile strength of geotextile tube is 1.6×10^-1 cm/sec and 205.26 kN/m, respectively. As a result of filed test, when filled, geotextile tube does not attain the same as its unfilled theoretical diameter, but may reach approximately of 55 percent of the theoretical diameter. At the time, geotextile tubes were 12.56 m in circumference and filled to a height of about 2.2 m. This paper presents case study on field application and behavior analysis of the saemangum waterproof embankment donggin 1 division construction using geotextile tube.

송정헌 Song Jung-hun , 강문성 Kang Moon-seong , 송인홍 Song Inhong , 황순호 Hwang Soon-ho , 박지훈 Park Jihoon , 전상민 Jun Sang-min , 김계웅 Kim Kye-ung , 장정렬 Jang Jeong-ryeol

DOI: JKWST Vol.55(No.6) 167-175, 2013

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The objective of this study was to investigate the nutrient load balance in the reservoir irrigated paddy block during growing seasons. Idong reservoir irrigation paddy block of 10.3 ha in size was selected to collect hydrologic and water quality data. Irrigation, canal flows, and paddy field drainage were measured using a water level gauge, while water samples were collected and analysed for water quality. The water balance analysis showed that 81 % and 75 % of total outflow were through paddy and irrigation canal drainage during 2011 and 2012, respectively. The water quality of paddy field drainage varied greatly depending on rice cultivation stage ranging from 0.05 to 24.55 mg/L and from 0.01 to 0.76 mg/L for T-N and T-P, correspondently. Paddy field drainage loads during May through June account for 64 % and 76 % in 2012 and 2013, while 82 % and 81 % for T-P in 2011 and 2012, respectively. The Pearson correlation analysis showed that rainfall was significantly correlated with nutrient loads during July through August due to runoff, and irrigation was related with nutrient loads of drainage during some period of July through September due to irrigation return flow. This study results showed characteristics of inflow and outflow nutrient loads from plentiful irrigated paddy block.

이예은 Lee Ye Eun , 김상민 Kim Sang Min

DOI: JKWST Vol.55(No.6) 177-186, 2013

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The purpose of this study was to analyze the temporal and spatial characteristics of the stream flow of small rural streams for investigating the status of stream depletion located downstream of irrigation reservoir. Bonghyun and Hai reservoirs and each downstream were selected for this study. Streamflow was measured for 8 stations downstream from two reservoirs from 2010 to 2012. The water quality samples were collected monthly from the 8 stream stations and 2 reservoir stations from 2011 to 2012. The stream depletion was found in most of the downstream of reservoirs for the non-irrigation period and even in the irrigation period when there were a lot of antecedent precipitation. We found that the stream segments where there were few streamflow, vegetation covers the stream and block the streamflow which makes the stream lost its original function as a stream. Water quality monitoring results of Bonghyun stream indicated that the concentration of SS, Turbidity, TOC, COD were decreased as the stream flows from the reservoir to downstream while the TN and TP were increased. The correlation analysis for water quality data indicated that the correlation between T-N and T-P was high for Bonghyeon and Sukji streams, respectively. Continuous monitoring for rural streams located in downstream of reservoirs are required to quantify the status of stream flow depletion and determine the amount of environmental flows.

손재권 Son Jae Gwon , 고남영 Goh Nam Young , 최진규 Choi Jin Kyu , 김학원 Kim Hak Won

DOI: JKWST Vol.55(No.6) 187-196, 2013

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This study is focused on analyzing the deformation types of seaside armor stones based of field survey in order to establish the cause of abrasion following the deformation of seaside armor stones. 1. The deformation of seaside armor stone in saemangeum sea dike was classified as three different types: floating, deviation, and abrasion. 2. It was discovered that the stones floated to the extent of maximum 50 m, as the result of inspecting floating stones which were situated on different ten places. 3. The average number of deviation in the high ocean wave section was four times more than that in the ordinary ocean wave section, as a result of comparing the deviation number of the ordinary ocean wave section and that of the high ocean wave section for the purpose of inspecting the relation between the deviation of armor stones and the effects of ocean wave. 4. The angular shape of armor stones seen in the initial construction period has been abraded smoothly, as result of comparing of the shape change of armor stones for the purpose of inspecting abrasion state of seaside armor stones. 5. It was discovered that the abrasion of armor stone was severe in the section of many floating stones, as a result of analyzing the levels of abrasion and the cumulative sections of floating stones for the purpose of investigating the cause of abrasion.