• Korean Journal of Soil Science and Fertilizer
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• v.30 no.3
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• pp.265-271
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• 1997

The salt accumulation, and chemical properties of 90 samples of the plastic film house soil in the area of Cheongju and Chungju were surveyed. Soil textural distribution of soil samples was 30% for sandy loam, 27% for loam and 43% for silty loam. Percentage distribution of electrical conductivity(EC) of surface soil was 23% below $2dS\;m^{-1}$, 30% for $2{\sim}4dS\;m^{-1}$, 25% for $4{\sim}6dS\;m^{-1}$ and 22% over $6dS\;m^{-1}$. Salt affected soil, which EC was higher than $4dS\;m^{-1}$, covered nearly 50% of all field surveyed. However subsoils(20~30cm) below $2dS\;m^{-1}$ was 68%. Salts in plastic film house soil was accumulated by increasing the cultivation period. After 5 years of cultivation electrical conductivity in plastic house soil was generally higher than $4.47dS\;m^{-1}$ in EC that was 2.8~5.6 times higher than that in the field soil in the outside of plastic film house. As the result of temporary removal of plastic film cover from the house during the rainy summer season, salt content in soil was decreased from $3.54{\sim}7.36dS\;m^{-1}$ to $0.71{\sim}2.92dS\;m^{-1}$ in EC due to the desalinization by runoff and percolating water. Contents of $NO_3-N$, $SO_4-S$ and Cl in plastic film house soil were 2.5. 7.0 and 3.4 times higher than those of open field respectively.

• Korean Journal of Ecology and Environment
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• v.38 no.1 s.110
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• pp.118-127
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• 2005

The comparison of water balance and nutrient loading from paddy field with different irrigation management were carried out during 1999 ${\sim}$ 2002 at two different sites; one is irrigated with groundwater and the other is irrigated with surface water. For the surface water irrigated paddy field, irrigation was performed continuously during growing season. Whereas, initial irrigation with groundwater was applied during initial growing season, and the ponded water depth was maintained by natural precipitation since initial irrigation. The runoff frequency of groundwater irrigated paddy field was less than that of surface water irrigated paddy field. The nutrient concentration of ponded water was high by fertilization at early cultural periods, so reducing surface drainage during fertilization period can reduce nutrient loading from paddy fields. Amount of irrigation water to surface water irrigated paddy field was higher than to groundwater irrigated paddy field and evapotranspiration was similar because it is influenced by climate. Overall input in and output from paddy field irrigated with goundwater were less than that with surface water. This study indicate that efficient water management can reduce surface drainage outflow, save water, and protect water quality. It might be important BMPs for paddy field.

• Journal of Korea Water Resources Association
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• v.53 no.6
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• pp.437-450
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• 2020

This study presents a probabilistic distributed hydrological model for Ephemeral catchment, where zero flow often occurs due to the influence of distinct climate characteristics in South Korea. The gridded hydrological model is developed by combining the Sacramento Soil Moisture Accounting Model (SAC-SMA) runoff model with a routing model. In addition, an error model is employed to represent a probabilistic hydrologic model. To be specific, the hydrologic model is coupled with a censoring error model to properly represent the features of ephemeral catchments. The performance of the censoring error model is evaluated by comparing it with the Gaussian error model, which has been utilized in a probabilistic model. We first address the necessity to consider ephemeral catchments through a review of the extensive research conducted over the recent decade. Then, the Yongdam Dam catchment is selected for our study area to confirm the usefulness of the hydrologic model developed in this study. Our results indicate that the use of the censored error model provides more reliable results, although the two models considered in this study perform reliable results. In addition, the Gaussian model delivers many negative flow values, suggesting that it occasionally offers unrealistic estimations in hydrologic modeling. In an in-depth analysis, we find that the efficiency of the censored error model may increase as the frequency of zero flow increases. Finally, we discuss the importance of utilizing the censored error model when the hydrologic model is applied for ephemeral catchments in South Korea.

• Journal of Korea Water Resources Association
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• v.40 no.11
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• pp.877-886
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• 2007

An urban drainage system consists of two major systems : flood drainage facilities and operating practices. The facilities are composed of sewer networks, gates, and pumping stations and the operating practice consists of pump or gate operation. Then, a real time simulation system which is able to simulate urban runoff and the pump operation and to consider the backwater effect is required to operate efficiently the pump. With this system, the efficient pump operating rule can be developed to diminish the possible flood damage on urban areas. In this study, a real time simulation system was developed using the SWMM 5.0 DLL and Visual Basic 6.0 equipped with EXCEL. Also, for developing efficient pump operating Rules, two new Rules were suggested. The first Rule is designed to operate pumps considering the condition of sewer networks such as depths of each junction. The second is to discharge all the amount of inflow at each time step. Results obtained by those Rules were compared with one by the current pump operating Rule which is able to consider only the depth of the retard basin. The developed model was applied to Joonggok retard basin and verified their applicability.

• Journal of Korea Water Resources Association
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• v.50 no.3
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• pp.169-179
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• 2017

Recently, due to global warming and climate change in Korea, local heavy storm occurs frequently. In this study, the risky areas for flooding in urban areas are analyzed for flood inundation based on two-dimensional urban flood runoff model (XP-SWMM) focusing on coastal high flood-risk urban areas. In addition, the MCDM (Multi-Criteria Decision Making) technique is utilized in order to establish the flood defense structural measures. The alternative flood reduction method are compared and the optimum flood defense measures are selected. A simulation model was used with three structural flood prevention measures (drainage pipe construction, water detention, flood pumping station). In order to decrease the flooding area, flood assessment criteria are suggested (flooded area, maximum inundation depth, damaged residential area, construction cost). Priorities of alternatives are determined by using compromise programming. As a result, the optimal flood defence alternative suggested for Janghang Zone 1 is flood pumping station and for Janghang Zone 2, 3 are drainage pipe construction.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.304-313
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• 2018

Agricultural land reclamation in Saemangeum tidal land project is mostly planned to be completed by 2020. Irrigation water for the land is required to be prepared by that time. However, water quality for the irrigation sources is barely meet the target concentration. This paper described the reduction effect of and policy consideration for best management practices (BMPs) which were fertilizer prescription by soil test (SO#1), mixed application of SO#1 and 3 (SO#2), drainage gate control (SO#3), time-release fertilizer application (SO#4), and control (CT). Reduction of paddy runoff was relatively higher in SO#3 (25%) and SO#1 (27%) while lower in SO#4 (9%) and SO#2 (7%) than that in CT. In addition, farmers promised to follow the BMP guidelines but they didn't because of the several problems caused for the BMPs implementation. Thus, it recommended developing an automated control of irrigation gate and paddy water depth and supporing farmers for NPS pollution control and irrigation water reduction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.839-850
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• 2018

The flood damage in urban areas due to torrential rain is increasing with urbanization. For this reason, accurate and rapid flooding forecasting and expected inundation maps are needed. Predicting the extent of flooding for certain rainfalls is a very important issue in preparing flood in advance. Recently, government agencies are trying to provide expected inundation maps to the public. However, there is a lack of quantifying the extent of inundation caused by a particular rainfall scenario and the real-time prediction method for flood extent within a short time. Therefore the real-time prediction of flood extent is needed based on rainfall-runoff-inundation analysis. One/two dimensional model are continued to analyize drainage network, manhole overflow and inundation propagation by rainfall condition. By applying the various rainfall scenarios considering rainfall duration/distribution and return periods, the inundation volume and depth can be estimated and stored on a database. The Rainfall-Duration-Flooding Quantity (RDF) relationship curve based on the hydraulic analysis results and the Self-Organizing Map (SOM) that conducts unsupervised learning are applied to predict flooded area with particular rainfall condition. The validity of the proposed methodology was examined by comparing the results of the expected flood map with the 2-dimensional hydraulic model. Based on the result of the study, it is judged that this methodology will be useful to provide an unknown flood map according to medium-sized rainfall or frequency scenario. Furthermore, it will be used as a fundamental data for flood forecast by establishing the RDF curve which the relationship of rainfall-outflow-flood is considered and the database of expected inundation maps.

• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.13-22
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• 2023

The importance of preemptive flood preparation is growing as the importance of preparing for climate change increases due to record heavy rains in the Seoul metropolitan area in August 2022. Although it is responding to flood control through reservoirs and sediment sites, the government is preparing excellent spill reduction measures through a preliminary consultation system for Low Impact Development (LID). In this study, the depth of flooding was simulated when LID technologies were applied to the Sillim 2-drain region in Dorimcheon Stream basin, an urban stream, using XP-SWMM, a two-dimensional model. In addition, the analysis and applicability of the effect of reducing rainfall runoff for the largest rainfall in a day were reviewed, and it was judged to be effective as a method of reducing flooding in urban areas. Although there is a limitation in which the reduction effect is overestimated, it is thought that the LID technologies can be a significant countermeasure as a countermeasure for small-scale flooded areas where some flooding occurs after structural flooding measures are established.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6B
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• pp.503-512
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• 2009

Watershed models, which are a tool for water cycle mechanism, are classified as the distributed model and the lumped model. Currently, the distributed models have been more widely used than lumped model for many researches and applications. The lumped model estimates the parameters in the conceptual and empirical sense, on the other hand, in the case of distributed model the first-guess value is estimated from the grid-based watershed characteristics and rainfall data. Therefore, the distributed model needs more detailed parameter adjustment in its calibration and also one should precisely understand the model parameters' characteristics and sensitivity. This study uses Jungnang basin as a study area and $Vflo^{TM}$ model, which is a physics-based distributed hydrologic model, is used to analyze its parameters' sensitivity. To begin with, 100 years frequency-design rainfall is derived from Huff's method for rainfall duration of 6 hours, then the discharge is simulated using the calibrated parameters of $Vflo^{TM}$ model. As a result, hydraulic conductivity and overland's roughness have an effect on runoff depth and peak discharge, respectively, while channel's roughness have influence on travel time and peak discharge.

• Journal of Korean Society of Forest Science
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• v.84 no.4
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• pp.465-478
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• 1995

The objective of this study was to investigate the impacts of large-scale timber harvesting on the environment of a mature hardwood forest. To achieve the objective, the effects of harvesting on forest environmental factors were analyzed quantitatively using the field data measured in the study sites of Seoul National University Research Forests [(Mt.) Paekunsan] for two years(1993-1994) following timber harvesting. The field data include information on vegetation, soil mesofauna, physicochemical characteristics of soil, surface water runoff, water quality in the stream, and hillslope erosion. For comparison, field data for each environmental factor were collected in forest areas disturbed by logging and undisturbed, separately. The results of this study were as follows : The diversity of vegetational species increased in the harvested sites. However, the similarity index value of species between harvested and non-harvested sites was close to each other. Soil bulk density and soil hardness were increased after timber harvesting, respectively. The level of organic matter, total-N, avail $P_2O_5$, CEC($K^+$, $Na^+$, $Ca^{{+}{+}}$, $Mg^{{+}{+}}$) in the harvested area were found decreased. While the population of Colembola spp., and Acari spp. among soil mesofauna in harvested sites increased by two to seven times compared to those of non-harvested sites during the first year, the rates of increment decreased in the second year. However, those members of soil mesofauna in harvested sites were still higher than those of non-harvested sites in the second year. The results of statistical analysis using the stepwise regression method indicated that the diversity of soil mesofauna were significantly affected by soil moisture, soil bulk density, $Mg^{{+}{+}}$, CEC, and soil temperature at soil depth of 5(0~10)cm in the order of importance. The amount of surface water runoff on harvested sites was larger than that of non-harvested sites by 28% in the first year and 24.5% in the second year after timber harvesting. The level of BOD, COD, and pH in the stream water on the harvested sites reached at the level of the domestic use for drinking in the first and second year after timber harvesting. Such heavy metals as Cd, Pb, Cu, and organic P were not found. Moreover, the level of eight factors of domestic use for drinking water designated by the Ministry of Health and Welfare of Korea were within the level of the first class in the quality of drinking water standard. The study also showed that the amount of hillslope erosion in harvested sites was 4.77 ton/ha/yr in the first year after timber harvesting. In the second year, the amount decreased rapidly to 1.0 ton/ha/yr. The impact of logging on hillslope erosion in the harvested sites was larger than that in non-harvested sites by seven times in the first year and two times in the second year. The above results indicate that the large-scale timber harvesting cause significant changes in the environmental factors. However, the results are based on only two-year field observation. We should take more field observation and analyses to increase understandings on the impacts of timber harvesting on environmental changes. With the understandings, we might be able to improve the technology of timber harvesting operations to reduce the environmental impacts of large-scale timber harvesting.