Y. G. Her , M. S. Kang , S. W. Park

DOI: JKWST Vol.48(No.7) 3-14, 2006

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The objective of this study was to develop a GIS-based decision support system (GIS-USLE system) to estimate soil erosion and evaluate its effect on concentrated upland plots in Godang district, Korea. This system was developed for the ArcView environment using A VENUE script. Three modules were used in the GIS-USLE system, namely pre-processing, the USLE factors calculator module, and post-processing. This system benefits from a user friendly environment that allows users with limited computer knowledge to use it. This system was applied to 1,285 individual upland plots ranging from 0.005 to 1.347 ha in size with an average slope steepness of 14 %. The rainfall distributions were estimated using the three methods, namely Mononobe and Yen-Chow with Triangle and with Trapezoid type, and then used to calculate the rainfall erosivity factor. The soil erosion amounts from the 1,285 individual plots in the study area by 2 year return period with a 24h maximum rainfall amount of 154.6 mm were estimated at 5 tons/ha on average. Slope appeared to be the most important factor affecting soil erosion estimation, as expected. The prototype model was applied to the project area, and the results appeared to support the practical applications. By examining many fields simultaneously, this system can easily provide fast estimation of soil erosion and thus reveal the spatial pattern of erosion from fields in a region. This study will help estimate and evaluate soil erosion in concentrated upland districts and identify the best management practices.

Kim Seong Joon , Lee Mi Seon , Kim Sang Ho , Park Genn Ae

DOI: JKWST Vol.48(No.7) 17-22, 2006

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Potential application topics of KOMPSAT-3 image in the field of precision agriculture are suggested. The topics can be categorized as fundamental and applied ones that have contents of static and dynamic characteristics respectively. As fundamental topics, precision information of agriculture that is related to farmland and its crop attributes, precision information of rural infrastructure that is related to rural village and its facilities, precision information of stream environment that is related to rural water resources and its facilities, and precision information of eco-environment that is especially related to riparian ecology and environmental status are included. As applied topics, precision rural water resources that has thematic contents of continuous and event-based runoff, spatial and temporal soil moisture and evapotranspiration, precision agricultural watershed environment that has the contents of spatial and temporal soil loss, sediment and pollutants transport, and precision temporal and spatial crop growth that has the contents of temporal crop texture, spectral reflectance, leaf area index, spatial crop protein information.

Sung Chan Yong , Kim Jong Hyouk

DOI: JKWST Vol.48(No.7) 25-31, 2006

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Permeable polymer concretes can be applied to roads, sidewalks, river embankment, drain pipes, conduits, retaining walls, yards, parking lots, plazas, interlocking blocks, etc. This study was to explore a possibility of using bottom ash as filler and recycled coarse aggregate of industrial by-products for permeable polymer concrete. The tests carried out at 20±1℃ and 60±20% relative humidity. At 7 days of curing, unit weight, void ratio, compressive and flexural strength and coefficient of permeability ranged between 1,652~1,828kgf/㎥, 15~29%, 18.2~24.5 MPa, and 6.8×10^-2~1.7×10^-1 ㎝/s respectively. It was concluded that the bottom ash and recycled coarse .aggregate can be used in the permeable polymer concrete.

Lee Dal Won

DOI: JKWST Vol.48(No.7) 35-43, 2006

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This study was carried out to investigate the liquefaction behaviour and predict deviator stress with matric suction, of unsaturated silty sand. The unsaturated soil tests were conducted using a modified triaxial cell and specimens were prepared using the moisture tamping method. The axis translation technique was used to create the desired matric suctions in the specimen. Undrained triaxial compression tests were carried out at matric suction of 0, 2, 5, 10 and 25 kPa. The specimens were sheared to axial strains of about 20% to obtain steady state conditions. The results showed that liquefaction of silty sand only occurs at matric suction of 0 kPa and 2 kPa. The results also show that at matric suctions of 5, 10 and 25 kPa, the resistance to liquefaction increases. As the suction increases, the undrained effective stress path approached the drained stress path. Also, the predicted and measured maximum deviator stress for unsaturated soils using the effective stress concept showed good agreement as matric suction increases. The deviator stress increase is nonlinear as matric suction increases.

Kim Yong-seong

DOI: JKWST Vol.48(No.7) 45-52, 2006

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A cyclic viscoelastic-viscoplastic constitutive model for clay is incorporated into an effective stress based seismic response analysis to describe viscous effect of clay layer to sand layer during earthquake. The seismic response against main shock of 1995 Hyogoken Nambu Earthquake is analyzed in the present study. Acceleration responses in both clay layer and just upper liquefiable sand layer are damped due to viscous effect of clay. A cyclic viscoelastic-viscoplastic constitutive model for clay was implemented into a FEM code, and Newmark-β method was employed for the time discretization in the finite element formulation. Seismic responses were simulated by numerical method with recorded data at Port Island, Kobe, Japan. As results of this study, it was found that a cyclic viscoelastic-viscoplastic constitutive model can give good description of dynamic behavior characteristics including viscoelastic effect.

Young-ju Ham , Song-bae Kim , Min-kyu Kim , Seong-jik Park

DOI: JKWST Vol.48(No.7) 55-63, 2006

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Bacterial transport models were evaluated in this study to determine the suitable model at describing bacterial transport in saturated column experiments. Four models used in the evaluation were: advective-dispersive equation (ADE) + equilibrium sorption/retardation (ER) + kinetic reversible sorption (KR) (Model I), ADE + two-site sorption (Model 2), ADE + ER + kinetic irreversible sorption (KI) (Model 3), ADE + KR + KI (Model 4). Firstly, analyses were performed with the first experimental data, showing that Model 4 is appropriate for describing bacterial transport. Even if Model 1 and 2 fit well to the observed data, they have a defect of not including the irreversible sorption, which is directly related to mass loss of bacteria. Model 3 can not properly describe the tailing observed in the data. However, further analysis with the second data indicates that Model 4 can not describe retardation of bacteria, even if the sorption-related parameters are varied. Therefore, Model 4 is modified by incorporating retardation factor into the model, resulting in the improved fitting to the data. It indicates that the transport model, into which retardation, kinetic reversible sorption, and kinetic irreversible sorption are incorporated, is suitable at describing bacterial transport in saturated column experiments. It is expected that the selected transport model could be applied to properly analyze the bacterial transport in saturated porous media.

Kwang-sik Yoon , Adel Shirmohammadi , Woo-jung Choi , Jae-woon Jung

DOI: JKWST Vol.48(No.7) 65-72, 2006

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Event mean concentration (EMC) of nitrogen (N) and phosphorus (P) is primary information for non-point source pollution assessment of a watershed. The EMCs for various types of agriculture such as dairy and crop farming under different climate and geologic conditions are not fully investigated. A diary- and crop-farming complex agricultural watershed in Piedmont region in Maryland, USA has been monitored for 10 years as a section 319 national monitoring program of US EPA. Dairy manure was the main source of fertilizer for crop farming in this watershed. Observed mean concentrations of N and P for each event were analyzed. Distribution of EMCs for N and P showed a wide range of variations. Representative EMCs of T-N and NO₃-N tended to be higher than those reported for other agricultural watersheds. This study confirmed that site-specific EMC information for various agricultural practices is required for better assessment of non-point source pollution using EMC method.

M. S. Kang , P. Srivastava , J. P. Fulton , T. Tyson , W. F. Owsley , K. H. Yoo

DOI: JKWST Vol.48(No.7) 73-86, 2006

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Concentrated poultry production in the State of Alabama, U.S.A. results in excessive poultry litter. Application of poultry litter to pastures and row crops serves as a cheap alternative to commercial fertilizer. However, over the years, poultry litter application to perennial forage crops in the Appalachian Plateau region of North Alabama has resulted in phosphorus (P) buildup in soils. Phosphorus index (P-index) and comprehensive nutrient management plans (CNMP) are often used as a best management practice (BMP) for proper land application of litter. Because nutrient management planning is often not done for small animal feeding operations (AFOs), and also because, in case of excess litter, litter transportation infrastructure has not been developed, over application of poultry litter to near by area is a common practice. To alleviate this problem, optimal poultry litter management and transportation infrastructure needs to be developed. This paper presents a methodology to optimize poultry litter application and transportation through efficient nutrient management planning and transportation network analysis. The goal was accomplished through implementation of three important modules, a P-Index module, a CNMP module, and a transportation network analysis module within ArcGIS, a Geographic Information System (GIS). The CNMP and P-Index modules assist with land application of poultry litter at a rate that is protective of water quality, while the transportation network analysis module helps transport excess litter to areas requiring litter in the Appalachian Plateau and Black Belt (a nutrient-deficient area) regions. Once fully developed and implemented, such a system will help alleviate water quality problems in the Appalachian Plateau region and poor soil fertility problems in the Black Belt region by optimizing land application and transportation. The utility of the methodology is illustrated through a hypothetical case study.