• Korean Journal of Ecology and Environment
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• v.52 no.1
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• pp.21-27
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• 2019

Analysis of water quality distribution is very important for river water quality management. Recently, various studies have been conducted on the analysis of water quality distribution according to reduction methods of nonpoint pollutant. The objective of this study was to select the probability distributions of water quality constituents (T-N, T-P, COD, SS) according to the farming forms (control, slow release fertilizer, water depth control) during non-storm period in the paddy fields. The field monitoring was conducted monitoring site located in Baeksan-myun, Buan-gun, Jeollabuk-do, Korea during non-storm period from May to September in 2016. Our results showed that there were no differences in water quality among three different farming forms, except for SS of control and water depth control. K-S method was used to analyzed the probability distributions of T-N, T-P, COD and SS concentrations discharged from paddy fields. As a results of the fitness analysis, T-N was not suitable for the normal probability distribution in the slow release fertilizer treatment, and the log-normal probability distribution was not suitable for the T-P in control treatment. The gamma probability distribution showed that T-N and T-P in control and slow release fertilizer treatment were not suitable. The Weibull probability distribution was found to be suitable for all water quality constituents of control, slow release fertilizer, and water depth control treatments. However, our results presented some differences from previous studies. Therefore, it is necessary to analyze the characteristics of pollutants flowing out in difference periods according to various farming types. The result of this study can help to understand the water quality characteristics of the river.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.407-417
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• 2011

Nowadays, the high land use, mainly used for urbanization, is affecting runoff loads of non-point pollutants to increase. According to this fact, increasing runoff loads seems like to appear that it contributes to high ratio of pollution loads in the whole the pollution loads and that this non-point source is the main cause of water becoming worse quality. Especially, concentrated pollutants on the impermeable roads run off to the public water bodies. Also the coefficient of runoff from roads is high with a fast velocity of runoff, which ends up with consequence that a lot of pollutants runoff happens when it is raining. Therefore it is very important project to evaluate the quantity of pollutant loads. In this study, I computed the pollutant loadings depending on time and rainfall to analyze characteristics of runoff while first flush storm water and evaluated the runoff time while first flush storm water and rainfall based on the change in curves on the graph. I also computed contribution ratio to identify its impact on water quality of stream. I realized that the management and treatment of first flush storm water effluents is very important for the management of road's non-point source pollutants because runoff loads of non-point source pollution are over the 80% of whole loads of stream. Also according to the evaluation of runoff loads of first flush storm water for SS, run off time was shown under the 30 minute and rainfall was shown under the 5mm which is less than 20% of whole rainfall. These are under 5mm which is regarded amount of first flush storm water by the Ministry of Environment and it is judged to be because run off by rainfall is very fast on impermeable roads. Also, run off time and rainfall of BOD is higher than SS. Therefore I realized that the management of non-point source should be managed and done differently depending on each material. Finally, the contribution ratio of pollutants loads by rainfall-runoff was shown SS 12.7%, BOD 12.7%, COD 15.9%, T-N 4.9%, T-P 8.9%, however, the pollutants loads flowing into the steam was shown 4.4%. This represents that the concentration of non-point pollutants is relatively higher and we should find the methodical management and should be concerned about non-point source for improvement on water quality of streams.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3983-3989
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• 2014

As the storm water runoff characteristics in urban areas have changed owing to urbanization, centralized facilities to reduce the urban flood runoff had been implemented. On the other hand, because they have their limitations, LID (Low Impact Development) of the distributed facilities for storm water runoff reduction is being actively planned and applied. The purpose of this study was to analyze the runoff characteristics for the spatial distribution of typical LID element techniques. This study set a study basin consisting of the five subbasins with the same basin and drainage systems, and analyzed the flood runoff characteristics from the two scenarios, one is for the locations and the other is for the number of green roofs (GR) and permeable pavement (PP), respectively, selected as typical LID element techniques. The SWMM implementation results showed that GR reduces 11.07% of the total and 3.42% of the peak amounts of storm water runoff, and PP leads to 18.09% of the total and 17.94% of the peak discharge reduction for a subbasin. Such a reduction rate is constant regardless of the LID locations, and increases linearly with the number of LID applications. The different runoff reduction rates between the GR and PP applications appear to be due to the effects of the different hydraulic conductivities in the control parameters for each LID.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.239-248
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• 2008

The purpose of this study is to examine appropriate sub-basin division numbers that best reflect the hydrological characteristics of the basin so as to propose the criterion for dividing the sub-basin in analyzing flood runoff in the future. The characteristics of flood runoff variations were based on the WMS HEC-1 model, and the area in the upstream of the Dongbyeon water level observatory and the Geum-ho water level observatory was chosen for analysis, and examined the characteristics of the changes in flood runoff. First of all, in the targeted basin, if the sub-basin division number was 4 (that is, the area of the divided sub-basin was about 25% of the total area). Next, as the sub-basin division number gradually increased, the peak rate of runoff increased as well, and in case the sub-basin was not divided, the peak rate of runoff occurred at the earliest time. Given these results, the spatial change characteristics will be best reflected when the sub-basin is divided for analysis of flood runoff in such a way that the area of the divided sub-basin is about 25% of the total area of the basin. However, as these results are based on a limited number (4) of storms, more storm events and other basins need to be included in the review of the sub-basin division methodology.

• Membrane and Water Treatment
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• v.10 no.1
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• pp.45-55
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• 2019

Climate change has significantly affected the rainfall characteristics which can influence the pollutant build-up and wash-off patterns from the catchment. Therefore, this study explored the influence of varying rainfall characteristics on urban and agricultural runoff pollutant export using statistical approaches. For this purpose, Mann-Kendall and Pettitt's test were applied to detect the trend and breakpoint in rainfall characteristics time series. In addition, double mass curve and correlation analysis were used to drive the relationship between rainfall-runoff and pollutant exports from both catchments. The results indicate a significant decreased in total rainfall and average rainfall intensity, while a significant increased trend for antecedents dry days and total storm duration over the study periods. The breakpoint was determined to be 2013 which shows remarkable trend shifts for total rainfall, average rainfall intensity and antecedents dry days except total duration. Double mass curve exhibited a straight line with significant rainfall-runoff relationship indicates a climate change effect on both sites. Overall, higher pollutant exports were observed at both sites during the baseline period as compared to change periods. In agricultural site, most of the pollutants exhibited significant (p< 0.05) association with total rainfall, average rainfall intensity and total storm duration. In contrast, pollutants from urban site significantly correlated with antecedent dry days and average rainfall intensity. Thus, total rainfall, average rainfall intensity and total duration were the significant factors for the agricultural catchment while, antecedents dry days and average rainfall intensity were key factors in build-up and wash-off from the urban catchment.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.2
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• pp.91-99
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• 2017

The objective of this research was to investigate runoff characteristics of suspended solid (SS) and chemical oxygen demand (COD) from a paddy field watershed during storm events in the growing and non-growing seasons. Average of event mean concentration (EMC) of pollutants were 56.9 mg/L for SS and 23.9 mg/L for COD in the non-growing season and 50.3 mg/L for SS and 11.9 mg/L for COD in the growing season. The average EMC of SS in the study area was much lower than that in the uplands irrespective of cultivation, suggesting that paddy fields control soil erosion. This may be because flooding and wet soil in the growing season, and rice straw residue and stubble on the topsoil in the non-growing season reduce soil erosion. The changing tillage practice from fall tillage to spring tillage avoids soil erosion due to shortening of the tilled fallow period. However, the average EMC of COD in the non-growing season was about twice as much that in the growing season likely due to the runoff of organics like rice straw residues. The relationship between SS and COD loads and stormwater runoff volume was expressed by power function. The exponent for SS was higher than that for COD, suggesting that SS load increased with stormflow runoff more than COD load did. The mean SS and COD loads per storm during the non-growing season were much lower than those in the growing season, and therefore non-point source pollution in the growing season should be managed well.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.102-111
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• 2009

Turbid storm runoff from intensive highland agriculture area has emerged as the major problem of water quality deterioration in the upstream region of the Han River. High slope of the upland combined with high rate of fertilization and intensive plowing causes high rate of soil erosion, and subsequently high suspended sediment and phosphorus content in the runoff water. The variations of water quality during rain spells were surveyed for two years (2005 and 2006) in the Jawoon Stream that is one of hot spots of intensive horticulture discharging turbid storm runoff. SS and TP showed large increase according to the increase of flow rate, whereas TN and BOD showed less fluctuations. Mean EMCs of SS and TP measured for nine rain events were as high as $207mgSS{\cdot}L^{-1}$ and $0.27mgP{\cdot}L^{-1}$, respectively. The export coefficient of SS and TP per area of cultivated field were calculated as $11,912kgSS{\cdot}yr^{-1}{\cdot}km^{-2}$ and $785kgP{\cdot}yr^{-1}{\cdot}km^{-2}$, repectively, which are significantly higher than reports of other area. It can be concluded that SS and TP in the runoffs were high enough to impose major threat to aquatic habitats, and the highland agriculture should be the main target of water quality management or habitat conservation in the study area.

• Journal of Environmental Science International
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• v.14 no.1
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• pp.41-51
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• 2005

Using three-dimensional non-hydrostatical numerical model with one way double nesting technique, atmo­spheric circulation in the mountainous coastal region in summer was investigated from August 13 through 15, 1995. During the day, synoptic westerly wind blows over Mt. Mishrung in the west of a coastal city, Sokcho toward the East Sea, while simultaneously, easterly upslope wind combined with both valley wind from plain (coast) toward mountain and sea-breeze from sea toward inland coast blows toward the top of the mountain. Two different directional wind systems confront each other in the mid of eastern slope of the mountain and the upslope wind goes up to the height over 2 km, becoming an easterly return flow in the upper level over the sea and making sea-breeze front with two kinds of sea-breeze circulations of a small one in the coast and a large one in the open sea. Convective boundary layer is developed with a thickness of about 1km over the ground in the upwind side of the mountain in the west and a thickness of thermal internal boundary layer from the coast along the eastern slope of the mountain is only confined to less than 200 m. On the other hand, after sunset, no prohibition of upslope wind generated during the day and downward wind combined with mountain wind from mountain towardplain and land-breeze from land toward under nocturnal radiative cooling of the ground surfaces should intensify westerly downslope wind, resulting in the formation of wind storm. As the wind storm moving down along the eastern slop causes the development of internal gravity waves with hydraulic jump motion in the coast, bounding up toward the upper level of the coastal sea, atmospheric circulation with both onshore and offshore winds like sea-breeze circulation forms in the coastal sea within 70 km until midnight and after that, westerly wind prevails in the coast and open seas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1361-1375
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• 2013

The design flow considering nonstationarity is estimated to determine the design flood related to hydraulic structure quantitatively based on the design process for stream restoration in the Mokgamcheon watershed proposed by Lee et al. (2011). The purpose of this research is to suggest new ways that the design flood was calculated considering nonstationarity at the Mokgamcheon watershed. Storm-unit hydrograph method to calculate design flood and direct frequency analysis were applied and nonstationarity was considered for the frequency analysis through extRemes toolkit developed at NCAR (National Center for Atmospheric Research). Although the method of direct flood frequency analysis due to dealing with flowrates directly has a more reliable than strom-unit hydrograph method, as a result, the method of direct flood frequency analysis underestimated the design flood than strom-unit hydrograph method due to the characteristics of the flow data. Therefore, the flood of storm-unit hydrograph method (100 years frequency) was determined as the design flood in the Mokgamcheon watershed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.295-302
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• 2007

Abnormally high waves occurring at the east coast of korea were observed at five field measurement stations and their characteristics were analyzed with the use of wind data provided by the Korean Meteorological Administration. The high waves occurred because strong Donghae twister that was developed by extratropical cyclone blew while high swell arrived at the east coast of Korea. At Sokcho, the most northern site among the five measurement stations, maximum gust speed was 63.7 m/s and significant wave height reached at its maximum of 9.69 m with the corresponding peak wave period of 12.8 s. The reason for appearance of the abnormally high waves is that high swell continued while the twister blew strongly. Moreover, the wind direction was the same as the direction of swell propagation, which maximizes the increase of wave height due to superposition of swell and wind-generated waves. On the east coast of Korea, outbreak of this type of storm waves is very probable in winter season so that it is requested to establish a countermeasure of minimizing possible damage caused by the storm waves.