• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1533-1540
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• 2015

In order to demonstrate the flow properties of the river bed and the design of hydraulic structures, the estimation of friction velocity is essentially required. However, existing friction velocity equations such as Log method and Power law have trouble to estimate the friction velocity because a boundary condition and various hydraulic properties are changed constantly in near the wall. In the present study, therefore, a new friction velocity equation that can minimize the parameters and reduce an error was suggested. To verify accuracy and reliability for the proposed equation, Clauser method, $\sqrt{gRI}$ method, reynolds stress method by Dr. Song were compared with the proposed method by estimated entropy parameter M for each channel. Consequently, the results show that uniform flow condition as well as non-uniform flow condition with highly accuracy nearly matched in case of accelerating non-uniform condition of $R^2=0.9621$, Decelerating Non Uniform condition of $R^2=0.9274$, Uniform condition of $R^2=0.8865$.

• Journal of Korea Water Resources Association
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• v.42 no.2
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• pp.161-168
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• 2009

The purpose of this study is to evaluate the variation of probability flood according to the flow regulation by multi-purpose dams (Soyang and Chungju) in the Han-river basin, Korea. SWAT-K (Soil and Water Assessment Tool-Korea) was used in order to generate regulated and unregulated daily streamflows upstream of Paldang dam. Simulated flow regulated by the Soyang and Chungju dams was calibrated by comparison with the observed inflow data at Paldang reservoir. Generally the ratio of flood flows to daily streamflows is known to decrease with drainage area in a watershed. Regulated and unregulated flood flows were obtained from the relationship between flood flows and daily streamflows. Extreme Type-I distribution was applied for flood frequency analysis and L-moment method was used for parameter estimation. This is a novel approach capable of understanding the variation in flood frequency with dam operation for the relatively large watershed scale, and this will helps improve the applicability of daily stream flow data for use in flood control as well as in water utilization.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.1
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• pp.99-118
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• 2012

The aim of this study is to define a correlation between spatial distribution characteristics of FFG(Functional Feeding Groups) of aquatic insects and related environmental factors in the Geum River based on the theory of RCC(River Continuum Concept). For that objective we had used SMRA(Stepwise Multiple Regression Analysis) method to analyze close relationship between the distribution of aquatic insects and the physical and chemical factors that may affect their inhabiting environment in the study area. And then, a probabilistic method named Frequency Ratio Model(FRM) and spatial analysis function of GIS were applied to produce a predictive distribution map of biota community considering their distribution characteristics according to the environmental factors as related variables. As a result of SMRA, the values of decision coefficient for factors of elevation, stream width, flow velocity, conductivity, temperature and percentage of sand showed higher than 0.5. Therefore these 6 environmental factors were considered as major factors that might affect the distribution characteristics of aquatic insects. Finally, we had calculated RMSE(Root Mean Square Error) between the predicted distribution map and prior survey database from other researches to verify the result of this study. The values of RMSE were calculated from 0.1892 to 0.4242 according to each FFG so we could find out a high reliability of this study. The results of this study might be used to develop a new estimation method for aquatic ecosystem with macro invertebrate community and also be used as preliminary data for conservation and restoration of stream habitats.

• Journal of Korea Water Resources Association
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• v.40 no.12
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• pp.995-1005
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• 2007

This study presents a framework for optimum scale determination for small hydropower development in a river basin. The framework includes the construction of hydrology and topography data, the simulation of hydropower operation, the economic analysis, and the determination of optimum scale of the small hydropower. The optimum scale of design flow and facility are determined by Net Present Value among economic analysis indices. The investment cost is estimated by the cost function derived from the construction cost of existing small hydropower plants. The benefit from power generation is estimated by the price announced by government. The presented framework is applied to the two potential sites in Cho River basin for the dam and run-of-river type of plants. Finally, the sensitivity analysis for a design flow and scale of the plant is performed for the each site. The usage of the framework presented in the study is highly expected for the estimation of potential hydropower resources or the decision support tool for a proprietor by estimating the optimum scale and economical feasibility in advance.

• Journal of Soil and Groundwater Environment
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• v.11 no.5
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• pp.9-19
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• 2006

The accurate estimation of groundwater recharge is important for the proper management of groundwater systems. The widely used techniques of groundwater recharge estimation include water table fluctuation method, baseflow separation method, and annual water balance method. However, these methods can not represent the temporal-spatial variability of recharge resulting from climatic condition, land use, soil storage and hydrogeological heterogeneity because the methods are all based on the lumped concept and local scale problems. Therefore, the objective of this paper is to present an effective method for estimating groundwater recharge with spatial-temporal variability using the SWAT model which can represent the heterogeneity of the watershed. The SWAT model can simulate daily surface runoff, evapotranspiration, soil storage, recharge, and groundwater flow within the watershed. The model was applied to the Musimcheon watershed located in the upstream of Mihocheon watershed. Hydrological components were determined during the period from 2001 to 2004, and the validity of the results was tested by comparing the estimated runoff with the observed runoff at the outlet of the catchment. The results of temporal and spatial variations of groundwater recharge were presented here. This study suggests that variations in recharge can be significantly affected by subbasin slope as well as land use.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.11-22
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• 2019

The objective of this study was to improve the cross-sectional area and height estimation method using stream width. Stream water levels should be calculated together to simulate inundation of agricultural land. However, cross-sectional survey data of small rural rivers are insufficient. The previous study has developed regression equations between the width and the cross-sectional area and between the width and the height of stream cross-section, but can not be applied to a wide range of stream widths. In this study, cross-sectional survey data of 6 streams (Doowol, Chungmi, Jiseok, Gam, Wonpyeong, and Bokha stream) were collected and divided into upstream, midstream and downstream considering the locations of cross-sections. The regression equations were estimated using the complete data. $R^2$ between the stream width and cross-sectional area was 0.96, and $R^2$ between width and height was 0.81. The regression equations were also estimated using divided data for upstream, midstream and downstream considering the locations of cross-sections. The range of $R^2$ between the stream width and cross-sectional area was 0.86 - 0.91, and the range of $R^2$ between width and height was 0.79 ? 0.92. As a result of estimating the cross-sections of 6 rivers using the regression equations, the regression equations considering the locations of cross-sections showed better performance both in the cross-sectional area and height estimation than the regression equations estimated using the complete data. Hydrologic Engineering Center - River Analysis System (HEC-RAS) was used to simulate the flood stage analysis of the estimated and the measured cross-sections for 50-year, 100-year, and 200-year frequency floods. As a result of flood stage analysis, the regression equations considering the locations of cross-sections also showed better performance than the regression equations estimated using the complete data. Future research would be needed to consider the factors affecting the cross-sectional shape such as river slope and average flow velocity. This study can be useful for inundation simulation of agricultural land adjacent to an unmeasured stream.

• Journal of Korea Water Resources Association
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• v.38 no.7 s.156
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• pp.545-554
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• 2005

The detailed interdisciplinary surveys were conducted on the pattern of habitat use of dominant fishes during the spawning and adult stage. The hydraulic parameters of the depth and velocity, discharge, substrate cover streams, and distribution of fish in the Yeonggang, WiCheon, HoeCheon, GeochangwiCheon, CheongdoCheon, DanjangCheon (the Nakdong River Basin) were measured. The Habitat Suitability Criteria was developed for the two fish species (Zacco Platypus and Zacco Temmincki) and life stages(spawning and adult), habitat conditions (depth, velocity and covet). The Physical Habitat Simulation of the Instream Flow Incremental Methodology was applied to calculate for optimal flow and the ecological flow recommendation was proposed by choosing the largest one in the optimal flow. The ecological flow recommendation was $5.0\;m^3/s{\sim}10.0\;m^3/s$ (e.g., $6.5\;m^3/s$ in the NaeseongCheon). Also, the ecological flow recommendations were compared with the existing ecological flow and flow duration analysis.

• Journal of Cadastre & Land InformatiX
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• v.45 no.2
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• pp.161-173
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• 2015

The influence of climate change on rainfall patterns has triggered landslide and debris flow with casualties and property damage. This study constructed DSM and Orthophoto by using UAV surveying technique and evaluated landslide risk area by applying GIS data into the infinite slope stability model. As a result of the estimation of slope stability in a site, the slope instability has $SI{\leq}1.0$ with cover area 46,396m2, and the distribution percentage was 18.2%. The most dangerous section has $SI{\leq}0.0$ with its cover area 7,988m2, and the ratio was 0.8%. The reviews regarding the risk of landslide and debris flow risk by stability index and river channel analysis respectively help being able to designate the hazard zone due to heavy rainfall. Therefore the analysis result of this study will need to reinforce soil slope and plan their safety measures in the future.

• Journal of Korea Water Resources Association
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• v.44 no.12
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• pp.967-974
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• 2011

Based on daily time series from RDAPS numerical weather forecast, Streamflow prediction was simulated and the result of ESP analysis was implemented considering quantitative mid- and long-term forecast to compare the results and review applicability. The result of ESP, ESP considering quantitative weather forecast, and flow forecast from RDAPS numerical weather forecast were compared and analyzed with average observed streamflow in Guem River Basin. Through this process, the improvement effect per method was estimated. The result of ESP considering weather information was satisfactory relatively based on long-term flow forecast simulation result. Discrepancy ratio analysis for estimating accuracy of probability forecast had similar result. It is expected to simulate more accurate flow forecast for RDAPS numerical weather forecast with improved daily scenario including time resolution, which is able to accumulate 3 hours rainfall or continuous simulation estimation.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.467-476
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• 1999

This paper analyzed the behavior of fixed-bed catalytic reactor (FBCR) which synthesizing maleic anhydride(MA) from the selective oxidation of n-butane. The behavior of FBCR describing convection-diffusion-reaction mechanism is examined by using two-dimensional pseudohomogeneous plug-flow transient model, with the kinetics of Langmuir-Hinshelwood type. Prediction model is composed by optimum parameter estimation from temperature profile, yield and conversion of single FBCR on operating condition variations of Sharma's pilot-plant experiment. A double FBCR with same yield and conversion for single FBCR generated a $8.96^{\circ}C$ lower hot spot temperature than a single FBCR. We could predict parametric sensitivity according to the variation of possible operating condition (temperature, concentration, volumetric flow of feed reactant and coolant flow rate) of single and double FBCR. Double FBCR showed the behavior of more operating range than single FBCR. Double FBCR with nonuniform activities could assure safety operation condition for the possible variation of operating condition. Also, double FBCR had slightly higher than the single FBCR in conversion and yield.