• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.301-312
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• 2019

The importance of the dual drainage system model has increased as the urban flood damage has increased due to the increase of local storm due to climate change. The dual drainage model is a model for more accurately expressing the phenomena of surface flow and conduit flow. Surface runoff and pipe runoff are analyzed through the respective equations and parameters. And the results are expressed visually in various ways. Therefore, inundation analysis results of dual drainage model are used as important data for urban flood prevention plan. In this study, the applicability of the COBRA model, which can be interpreted by combining the dual drainage system with the natural watershed and the urban watershed, was investigated. And the results were compared with other dual drainage models (XP-SWMM, UFAM) to determine suitability of the results. For the same watershed, the XP-SWMM simulates the flooding characteristics of 3 types of dual drainage system model and the internal flooding characteristics due to the lack of capacity of the conduit. UFAM showed the lowest inundation analysis results compared with the other models according to characteristics of consideration of street inlet. COBRA showed the general result that the flooded area and the maximum flooding depth are proportional to the increase in rainfall. It is considered that the COBRA model is good in terms of the stability of the model considering the characteristics of the model to simulate the effective rainfall according to the soil conditions and the realistic appearance of the flooding due to the surface reservoir.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.571-580
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• 2013

In this study, compared with the result of water surface elevation and water velocity on the establishment of river maintenance basic plan and result of HEC-GeoRAS based GIS, and after use the result of water surface elevation and velocity were observed in the Han stream on Jeju island, analysis 2 dimensional stream flow. the lateral hydraulic characteristics and curved channel of the stream were analyzed by applying SMS-RMA2 a 2 dimensional model. The results of the analysis using HEC-RAS model and HEC-GeoRAS model indicated that the distribution ranges of water surface elevation and water velocity were similar, but the water surface elevation by section showed a difference of 0.7~2.18 EL.m and 0.63~1.16 EL.m respectively, and water velocity also showed differences of maximum 1.58m/sec and 2.67m/sec. SMS-RMA2 analysis was done with the sphere of Muifa the typhoon as a boundary condition, and as a result, water velocity distribution was found to be 1.19 through 3.91 m/sec, and the difference of lateral water velocity in No. 97 through 99 the curved channel of the stream was analyzed to be 1.59 through 2.36 m/sec. In conclusion it is anticipated that the flow analysis of 2 dimension model of stream can reflect the hydraulic characteristics of the stream curved channel or width and shape, and can be applied effectively in the establishment of river maintenance basic plan or management and designing of stream.

• Korean Journal of Environmental Agriculture
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• v.24 no.1
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• pp.12-16
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• 2005

As a silicate source to rice, a coal ash was selected and mixed with phosphor-gypsum (50:50, wt $wt^{-1}$) to reduce the potential of boron toxicity and to supply calcium element. We expected that high con tent of calcium in this mixture might convert water-soluble phosphorus to less soluble forms and then reduce the release of soil phosphorus to surface runoff. The mixture was applied with the rate of 0, 20, 40, and 60 Mg $ha^{-1}$ in paddy soil (Nagdong series, a somewhat excessively drained loamy fine sand) in Daegok, Jinju, Korea The mixture reduced significantly water-soluble phosphorus (W-P) in the surface soils by shifting from W-P and Fe-P to Ca-P and Al-P during whole rice cultivation. In contrast with W-P, plant available phosphorus increased significantly with the mixture application due to high content of phosphorus and silicate in the mixture. The mixture of coal ash and phosphor-gypsum (50:50, wt $wt^{-l}$) would be a good alternative to reduce a phosphorus export in rice paddy soil together with increasing rice yields.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.7
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• pp.57-66
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• 2005

The Hydrological Simulation Program - FORTRAN (HSPF) was modified to simulate nonpoint pollutant loadings from paddy fields using a field experimental data collected during 2001-2002. The concept of a 'dike height' was added in a modified HSPF code, named HSPF-Paddy, to consider the function of retaining water by a weir at the field outlet. The effect of fertilization on the variances of nutrients on the soil surface and shallow soil layer was described mathematically with a Dirac delta function (or first-order kinetics). As confirmed through model verification, the HSPF-Paddy modifications were shown to represent the function of retaining water, varied ponded water, and surface runoff by forced drain during both rainy and non-rainy seasons and reasonably predicted the water balance and nutrients behavior in paddy fields. It is a distributed watershed model which, with the paddy modifications, can now simulate nonpoint pollutant loadings where paddy fields are dominant, and it can be used to evaluate the effects of paddy fields on the water quality at a basin scale, and assess the impacts of proposed BMPs applied to paddy fields.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.6
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• pp.109-118
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• 2003

As a fundamental research to establish a safety operation plan for irrigation dams, this study presents hydrologic analysis conducted in Sungju Dam watershed based on various rainfall data. Especially those reservoirs without flood control feature are widely exposed to the risk of flooding, a safe and optimized operation program need to be improved against arbitrary flooding. In this study, reservoir routing program was developed and simulated for reservoir runoff estimation using WMS hydrology model. The model simulated the variations of reservoir elevation under the condition of open or closed emergency gate. In case of closed emergency gate, water surface elevation was given as 193.15 m, and this value exceeds the dam crest height by 1.65 m. When the emergency gate is open, the increment of water surface elevation is given as 192.01 m, and this value exceeds dam crest height by 0.57 m. As an alternative plan, dam height increase can be considered for flood control under the PMP (Probable Maximum Precipitation) condition. Since the dam size is relatively small compare to the watershed area, sound protection can be expected from the latter option rather than emergency gate installation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.3
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• pp.36-46
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• 1993

The purposes of this study are to develop three-layered Green-Ampt infiltration model considering temporal variation of physical properties of soil and to evaluate the model with field experiment on bare-tilled and soybean-growing soil plots under natural rainfalls. Infiltration tests were conducted on a sandy loam soil. The model has three-layered soil profile including a surface crust, a tilled layer, a subsoil and considers temporal variation of porosity, hydraulic conductivity, capillary pressure head on a tilled layer by natural rainfalls and canopy density variation of crop. Field measurement of porosity, average hydraulic conductivity and average capillary presure head on a tilled layer were conducted by soil sampler and air-entry permeameter at regular intervals-after tillage. It was found that temporal variation of porosity and average hydraulic conductivity might be expressed as a function of cumulative rainfall energy and average capillary pressure head might be expressed as a function of porosity of a tilled soil. The model was calibrated by an optimization technique, Hooke and Jeeves method using hourly surface runoff data. With the calibrated parameters, the model was verified satisfactorily.

• Ocean and Polar Research
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• v.25 no.1
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• pp.75-87
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• 2003

The water balance calculation in the IRL shows that fresh groundwater discharge is the primary factor, with surface runoff from gaged and ungaged areas as the second freshwater contributor. Precipitation and evaporation are almost in balance fer the entire IRL. Due to high freshwater discharge from ground-water, the annual net flow is outward from the IRL to the continental shelf of the Atlantic Ocean resulting in a relatively short flushing time, denoted as $T_{0.5}$ (50% flushing time) and $T_{0.99}$ (99% flushing time). $T_{0.5}$, and. $T_{0.99}$ without a tidal effect in the Northern IRL are 17 and 114 days, respectively, during the dry season. During the wet season, they are 10 and 65 days, respectively. Tidal flushing effects are considered in central IRL due to the proximity to Sebastian Inlet. In the Northern Central zone during dry season, $T_{0.5}$, and. $T_{0.99}$ are 6 and 43 days, respectively and during the wet season 5 and 33 days. In the Southern Central zone they are 2 and 16 days for the dry season,2 and 15 days for the wet season. High groundwater seepage into the IRL is considered to be a positive effect in maintaining relatively good water quality condition even with few narrow inlets.

• Journal of Environmental Science International
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• v.15 no.4
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• pp.359-364
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• 2006

Two sites with different average daily traffic volume at an intersection were selected in order to investigate water quality of the first flushes in the surface runoffs. The effects of rainfall intensities and accumulated non-rainy days before rainfall events on the water quality were also delineated. Samples were collected at every 2 min. interval from each first flush from February to May, 2004 for 4 major rainfall events. $COD_{cr}$ or SS concentrations at the site with an average daily traffic volume (ADTV) of 23,000 vehicles were 2-7 times higher than those at the site with an ADTV of 1,400 vehicles. The longer the accumulated non-rainy days were, the higher the concentration of heavy metals were than those of $COD_{cr}$ and SS in the first flushes.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.585-594
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• 2006

This study focused on the causes of fish kills and its prevention methods in Yudeung Stream, Daejeon, Korea. Intense field data, continuous water quality monitoring system and water quality modeling were applied to analyze the causes. Pollutant can be delivered to urban streams by surface runoff and combined sewer overflows in rainfall events. However, water quality analysis and water quality modeling results indicate that the abrupt fish kills in the Yudeung stream seems to be caused by combined effect of DO depletion, increase in turbidity and other toxic material. Excessive fish population in the study area may harm the aesthetic value of the stream and also has greater potential for massive fish kills. It is suggested to implement methods to reduce delivery of pollutants to the stream not only to prevent fish kills but also to keep balance of ecosystem including human uses. Frequent clean up of the urban surface and CSO, installation of detention basin will be helpful. In the long run, it seems combined sewer system has be replaced with separate sewer system for more effective pollutant removal in the urban area.

• Journal of The Geomorphological Association of Korea
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• v.23 no.3
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• pp.93-104
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• 2016

High school textbooks of world geography show geomorphic featuresin arid environments such as sand dune, yardang and ventifact which are largely created by aeolian processes. Desert pavements, ubiquitous armored surfaces composed of a mosaic of clasts in hot and arid regions, are introduced as a major landform which can be attributed to wind erosion. However, they are formed by a variety of processes including deflation, surface runoff, upward clast migration and dust accretion that cause coarse particles concentration at the surface. The deflation by wind leaving a lag of coarse clasts has been solely regarded at home, even though the classical mechanism of deflation has been evaluated as a relatively unimportant process of pavement formation abroad through empiricalstudies. The accretionary model is gaining wider acceptance, thus implying that desert pavements could be formed through deposition of aeolian material. In addition, sheetflood and upward migration of clasts, irrelevant to the aeolian processes, could also create stone pavements. As a consequence, the deflation process in high school textbooks has to be urgently modified into a range of processes including aeolian mantling. By stressing that desert pavements are an exceptional geomorphic feature in deserts where wind is a predominant geomorphic agent, they can be used as a good example to demonstrate that a landform is not monogenetic.