김성준 Kim Seong-joon , 신형진 Shin Hyung-jin , 박민지 Park Min-ji , 조형경 Joh Hyung-kyung , 정충길 Jung Chung-gill

DOI: JKWST Vol.53(No.2) 1-8, 2011

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In this study, In order to evaluate reliable of MODIS GPP, the MODIS GPP and Flux tower measured GPP were compared to evaluate the use of method on 8 days composite MODIS GPP. The 2008 Flux data (CO₂ Flux and air temperature) measured in Seolmacheon watershed (8.48 ㎢) were used. The Flux tower GPP was estimated as the sum of CO₂ Flux and Rec (ecosystem respiration) by Lloyd and Taylor method (1994). The summer Monsoon period from June to August mostly contributed the underestimation of MODIS GPP by cloud contamination on MODIS pixels. The 2008 MODIS GPP and Flux tower GPP of the watershed were 1133.2 g/㎡/year and 1464.3 g/㎡/year respectively and the determination coefficient (R²) after correction of cloud-originated errors was 0.74 (0.63 before correction). Even though effect of Cloud-Originated Errors was eliminated, Solar radiation and Temperature are affected at GPP. Measurement of correct GPP is difficult. But, If errors of MODIS GPP analyze on Cloud Moonsoon Climate in korea and eliminated effect of Cloud-Originated Errors, MODIS GPP will be considered GPP increasing of 9 %. There, Our results indicate that MODIS GPP show reliable and useful data except for summer period in Moonsoon Climate.

이주헌 Lee Joo Heon , 양승만 Yang Seung Man , 김성준 Kim Seong Joon , 강부식 Kang Boo Sik

DOI: JKWST Vol.53(No.2) 9-17, 2011

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Based on the statistical annual report, there are 17,649 reservoirs are operating for the purpose of agricultural water supply in Korea. 58 % of entire agricultural reservoirs had been constructed before 1948 which indicate the termination of required service life and rest of those reservoirs have also exposed to the dam break risk by extreme flood event caused by current ongoing climate change. To prevent damages from dam failure accident of these risky small size dams, it is necessary to evaluate and manage the structural and hydrological safety of the reservoirs. In this study, a simplified evaluation method for hydrologic safety of dam is suggested by using Rational and Creager formula. Hydrologic safety of small scale dams has evaluated by calculating flood discharge capacity of the spillway and compares the results with design frequency of each reservoir. Applicability and stability of suggested simplified method have examined and reviewd by comparing the results from rainfall-runoff modeling with dam break simulation using HEC-HMS. Application results of developed methodology for three sample reservoirs show that simplified assessment method tends to calculate greater inflow to the reservoirs then HEC-HMS model which lead lowered hydrologic safety of reservoirs. Based on the results of application, it is expected that the developed methodology can be adapted as useful tool for small scale reservoir's hydrologic safety evaluation.

우원희 Woo Won Hee , 장원석 Jang Won Seok , 김익재 Kim Ik Jae , 김기성 Kim Ki-sung , 옥용식 Ok Yong-sik , 김남원 Kim Nam Won , 전지홍 Jeon Ji-hong , 임경재 Lim Kyoung Jae

DOI: JKWST Vol.53(No.2) 19-26, 2011

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SATEEC ArcView GIS system was developed using the Universal Soil Loss Equation (USLE) and sediment delivery ratio (SDR) modules. In addition, time-variant R and C modules and R₅ module were developed and integrated into the SATEEC system in recent years. The SATEEC ArcView GIS 2.1 system is a simple-to-use system which can estimate soil erosion and sediment yield spatially and temporarily using only USLE input data, DEM, and daily rainfall dataset. In this study, the SATEEC 2.1 system was used to evaluate the effects of USLE LS input data considering slope length segmentation on soil erosion and sediment yield estimation. Use of USLE LS with slope length segmentation due to roads in the watershed, soil erosion estimation decreased by 24.70 %. However, the estimated sediment yield using SATEEC GA-SDR matched measured sediment values in both scenarios (EI values of 0.650 and EI 0.651 w/o and w/flow segmentation). This is because the SATEEC GA-SDR module estimates lower SDR in case of greater soil erosion estimation (without flow length segmentation) and greater SDR in case of lower soil erosion estimation (with flow length segmentation). This indicates that the SATEEC soil erosion need to be estimated with care for accurate estimation of SDR at a watershed scale and for accurate evaluation of BMPs in the watershed.

김영익 Kim Young Ik , 연규석 Yeon Kyu Seok , 김기성 Kim Ki Sung , 정종우 Jeong Jong Woo , 김용성 Kim Yong Seong

DOI: JKWST Vol.53(No.2) 27-33, 2011

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This study is a preliminary investigation into the development of a construction method that will protect a reservoir even during over flows caused by severe flooding. Through hydraulic modeling tests, the destructive phenomena caused by spillway-junction scour during reservoir overflow were modeled, and the effects on the embankment during such an overflow and the spillway-junction movements are discussed. The reservoir destruction model used the Tanbu reservoir, located in Gangwondo Chuncheon-si Namsanmyeon (H＝22 m, L＝115 m), as the model reservoir and created an embankment with a 1/60 ratio. We review the spillway-junction safety factor during overflow and embankment movement following reinforcement measures for three different cases: no reinforcement, cemented sand and gravel (CSG) reinforcement and water-blocking sheet reinforcement. The results of this study confirmed that when the spillway-junction is exposed to soil, it is very vulnerable to overflow and that a water-blocking sheet or CSG reinforcement are very effective measures in preventing embankment destruction in the long-term period.

김영익 Kim Young Ik , 연규석 Yeon Kyu Seok , 김기성 Kim Ki Sung , 유경완 Yoo Kyeong Wan , 김용성 Kim Yong Seong

DOI: JKWST Vol.53(No.2) 35-43, 2011

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This study aimed to investigate the engineering characteristics of PVA fiber-cement-soil mixture used to prevent or reduce brittle failure of cement-soil mixtures due to the tensile strength increase from the addition of a synthetic fiber. The engineering characteristics of PVA fiber-cement-soil mixtures composed of PVA fiber, soil, and a small amount of cement was analysed on the basis of the compaction test, the unconfined compression test, the tensile strength test, the freezing and thawing test, and the wetting and drying test. The specimens were manufactured with soil, cement and PVA fiber. The cement contents was 2, 4, 6, 8, and 10%, and the fiber contents was 0.4, 0.6, 0.8, and 1.0% by the weight of total dry soil. To investigate the strength characteristics depending on age, each specimen was manufactured after curing at constant temperature and humidity room for 3, 7 and 28 days, after which the engineering characteristics of PVA fiber-cement-soil mixtures were investigated using the unconfined compression test, the tensile strength test, the freezing and thawing test, and the wetting and drying test. The basic data were presented for the application of PVA fiber-cement-soil mixtures as construction materials.

김해도 Kim Hae Do , 김선주 Kim Sun Joo , 김필식 Kim Phil Shik

DOI: JKWST Vol.53(No.2) 45-52, 2011

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This study is to develop a Priority Decision System for Redevelopment (PDSR) which is able to decide the priority for redevelopment of agricultural reservoirs. The major scopes of this research are to make the related GIS data like hydrologic unit map and other thematic maps to determine the suggested priority index (PI), and to develop the PDSR handling the GIS data and calculating weighing factors for the PI. In order to make the weighing factor decision module, the AHP technique was adopted. The result of the weighing factor calculation was showed PC (Possibility Criteria) and RC (Restriction Criteria) were 76% and 24% respectively. Which means that most of the specialist selected PC category prior to RC because of whom to mostly of major technique. So, in order to make more objective result, the selection of specialists is important like environmental activists or local residents and so on. The product from this research can provide more scientific support to decide the priority decision.

우재열 Woo Jae Yeoul , 김진수 Kim Jin Soo , 장훈 Jang Hoon , 김영현 Kim Young Hyeon

DOI: JKWST Vol.53(No.2) 53-60, 2011

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This study was conducted to investigate the effect of hydropower factors (watershed, gross head), operation ratio and unit electricity cost on the benefit-cost ratio (B/C ratio) of small hydropower using agricultural reservoirs. The equation of B/C ratio was expressed as a function of watershed area, gross head, operation ratio and unit electricity cost. The benefit increased with watershed area, gross head and unit electricity cost, while the cost increased with watershed area and gross head but decreased with operation ratio. The B/C ratio increased with watershed area, gross head, operation ratio and unit electricity cost. While the effect of gross head on the B/C ratio decreased with watershed area, the effect of operation ratio and unit electricity cost on the B/C ratio increased with watershed area. The operation ratio is an important factor to affect the B/C ratio and therefore we need to develop hydropower for the heightened dams to expect high operation ratio due to continuous water release. The unit electricity cost is also an important factor to affect the B/C ratio and the B/C ratio was always below 1 unless unit electricity cost is over 60 Won/kWh under given conditions. The reservoirs with economic feasibility for small hydropower development were three in 21 when the equation of B/C ratio was appled to the study reservoirs. The results can be used to choose the appropriate reservoir with economic feasibility for development of small hydropower.

강연구 Kang Y. K. , 강금춘 Kang G. C. , 김종구 Kim J. K. , 김영화 Kim Y. H. , 장재경 Jang J. K. , 유영선 Ryu Y. S.

DOI: JKWST Vol.53(No.2) 61-66, 2011

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Biomass is considered to be a major potential fuel and renewable resource for the future. In fact, there is high potential to produce the large amount of energy from biomass around the world. In this study, to obtain basic data for practical application of agricultural and forest by-products as fuel of heating system in agriculture, agricultural and forest biomass resources were surveyed, the pelletizer with capacity of 50 kg · h^-1 was designed and manufactured and pellets were made by the pelletizer. High heating value, ash content, etc. of pellets made of agricultural and forest by-products were estimated. Straw of rice was the largest agricultural biomass in 2009 and the total amount of rice straw converted into energy of 299×10³ TOE. And in 2009, amount of forest by-product converted into energy of 9,579×10³ TOE. High heating values of pellets made of stem and seed of rape, stem of oat, rice straw and rice husk were 16,034, 16,026, 16,089, 15,650, 15,044 kJ · kg^-1 respectively. High heating values of pellets made of agricultural by-products were average 83.6% compared to that of wood pellet. Average bulk density of pellets made of stem and seed of rape, stem of oat, rice straw and rice husk was 1,400 kg · m^-3 (1.4 g · cm^-3). Ash contents of the pellets were 6.6, 7, 6.2, 5.5, 33% respectively. Rice husk pellet produced the largest ash content compared to other kinds of pellets.

원철희 Won Chul Hee , 최용훈 Choi Yong Hun , 신민환 Shin Min Hwan , 서지연 Seo Ji Yeon , 최중대 Choi Joong Dae

DOI: JKWST Vol.53(No.2) 67-74, 2011

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This research focused on the investigation of runoff and nonpoint sources (NPS) pollution characteristics from small soil box plots treated by livestock waste composts. An indoor rainfall simulation was performed over the plots for 60 minutes. Simulated rainfall intensities were 32.4, 43.2, 50.3 and 57.1 mm/hr respectively. Slope of soil box plots was 10° and 20°, respectively. Rainfall simulation replicated 5 times and the experiment was conducted every four days five times. As the slope of soil box increased, NPS pollution loads increased. And as rainfall intensity was increased from 32.4 to 57.1 mm/hr, NPS pollution loads gradually increased, too. Discharge of NPS pollution loads was the largest in the first simulation and thereafter decreased gradually. Discharged BOD load to the total applied load from 10° plots, ranged 0.2 to 0.7 %, was 8.4 to 50.0 % lower than slope 20° plots. When the application rate increased twice, the increase of pollution load was between 1.7～5.7 times. Analysis of Pearson's correlation coefficient showed that organic matter content in pig compost and NPS pollution loads were correlated well. While under liquid compost application, the correlation coefficients between them were not good. It was concluded that application of livestock resources need to consider long-term weather forecast and if necessary, NPS reduction measures must be preceded in order to reduce NPS pollution discharge.

김영익 Kim Young Ik , 연규석 Yeon Kyu Seok , 최중대 Choi Joong Dae , 김기성 Kim Ki Sung , 서지연 Seo Ji Yeon , 김용성 Kim Yong Seong

DOI: JKWST Vol.53(No.2) 75-82, 2011

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This study was performed to evaluate the water purification properties of bio-composites planting blocks using oyster shell and effective microorganism that have high absorption ability of heavy metals and organics to develop environmentally friendly river embankment technique contained various factors such as oyster shells, effective microorganism, porous concrete and planting embankment block. To maximize greening effect, the seeds were arbitrarily sown. In addition, in order to analyze the effect of water quality purification after the planting, the samples were collected from each designated zone 1, 7 and 30 days after steeping in water. Then, the samples were analyzed in terms of seven test items such as SS, BOD, COD, T-N, T-P, pH, etc. on the basis of the test method for water pollution. The following conclusions were reached from the test result. As a result of analysis for water quality purification for the concrete block containing the effective microorganism, it was found that the values for SS, BOD, T-N and T-P for the sample taken after 30 days were lower than the initial values, which indicated that the water purification effect had been created. The result of the water quality purification analysis for the concrete block containing oyster shell showed that the values for SS, BOD, COD and T-P for the sample taken after 30 days were lower than the initial values which also indicated that it had been effective in water quality purification.