• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.200-204
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• 2012

In engineering hydrology, an estimation of precipitation loss is one of the most important issues for successful modeling to forecast flooding or evaluate water resources for both surface and subsurface flows in a watershed. An accurate estimation of precipitation loss is required for successful implementation of rainfall-runoff models. Precipitation loss or hydrological abstraction may be defined as the portion of the precipitation that does not contribute to the direct runoff. It may consist of several loss elements or abstractions of precipitation such as infiltration, depression storage, evaporation or evapotranspiration, and interception. A composite loss rate model that combines four loss rates over time is derived as a lumped form of a continuous time function for a storm event. The composite loss rate model developed is an exponential model similar to Horton's infiltration model, but its parameters have different meanings. In this model, the initial loss rate is related to antecedent precipitation amounts prior to a storm event, and the decay factor of the loss rate is a composite decay of four losses.

• Journal of Korea Water Resources Association
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• v.52 no.11
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• pp.947-950
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• 2019

The main feature of this paper is to provide a driving control strategy to improve the primary clarifier treatment efficiency in the initial rainfall inflow. With the recent development of IoT technology and sensing technology, the basis for operation control of wastewater treatment facilities has been improved. As a result of improving the efficiency of treatment of primary clarifier using on-line measurement results, it is possible to minimize the outflow of untreated sewage and contribute to the improvement of operation efficiency of wastewater treatment plants.

• The Journal of Engineering Geology
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• v.27 no.4
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• pp.475-487
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• 2017

We performed landslide flume tests to analyze characteristics of landslide occurrence and change in the ground materials due to rainfall infiltration. The test apparatus is composed of flume, rainfall simulator, and measurement sensors and landslides were triggered by heavy rainfall (Intensity=200 mm/hr) sprinkled at the above of an artificial slope. The measurement sensors for matric suction and volumetric water content were installed with 3 sets at shallow (GL-0.2 m), middle (GL-0.4 m), and deep depth (GL-0.6 m) in the slope and the tests were performed with in-situ, loose, and dense condition of each weathered soils of granite, gneiss, and mudstone. The analyses show that surface erosion was dominant in initial time of the test due to heavy rainfall and then landslides occur following locally happened transverse tension cracks. The characteristics of landslide were both shallow failure because of a spread of wetting front induced by the rainfall infiltration and retrogressive failure. While the matric suction was decreased rapidly without any precursor in the soil saturation, the volumetric water content was increased gradually, reached its maximum value, and then decreased rapidly with landslide.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.4
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• pp.59-72
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• 1987

Although long-term runoff analysis is important as much as flood analysis in the design of water works, the technological level of the former is relatively lower than that of the latter. In this respect, the precise estimation model for the volume of successive runoff should he developed as soon as possible. Up to now, in Korea, Gajiyama's formula has been widely used in long-term runoff analysis, which has many problems in applying in real situation. On the other hand, in flood analysis, unit hydrograph method has been exclusively used. Therefore, this study aims at trying to apply unit hydrograph method in long-term runoff analysis for the betterment of its estimation. Four test catchment areas were selected ; Maesan area in Namlum river as a representative area of Han river system, Cheongju area in Musim river as one of Geum river system, Hwasun area in Hwasun river as one of Yongsan river system, and Supyung area in Geum river as one of Nakdong river system. In the analysis of unit hydrograph, seperation of effective rainfall was carried out firstly. Considering that effective rainfall and moisture condition of catchrnent area are inside and outside of a phenomenon respectively and the latter is not considered in the analysis, Initial base flow(qb)was selected as an index of moisture condition. At the same time, basic equation(Eq.7) was established, in which qb can take a role as a parameter in relating between cumulative rainfall(P) and cumulative loss of rainfall(Ld). Based on the above equation, computer program for estimation model of qbwas seperately developed according to the range of qb, Developed model was applied to measured hydrographs and hyetographs for total 10 years in 4 test areas and effective rainfall was estimated. Estimation precision of model was checked as shown in Tab- 6 and Fig.8. In the next stage, based on the estimated effective rainfall(R) and runoff(Qd), a runoff distribution ratio was calculated for each teat area using by computerised least square method and used in making unit hydrographs in each test area. Significance of induced hydrographs was tested by checking the relative errors between estimated and measured runoff volume(Tab-9, 10). According to the results, runoff estimation error by unit hydrograph itself was merely 2 or 3 %, but other 2 or 3 % of error proved to be transferred error in the seperation of effective rainfall. In this study, special attentioning point is that, in spite of different river systems and forest conditions of test areas, standardized unit hydrographs for them have very similar curve shape, which can be explained by having similar catchinent characteristics such as stream length, catchinent area, slope, and vegetation intensity. That fact should be treated as important factor ingeneralization of unit hydrograph method.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.581-589
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• 2012

Non-point source pollutant is exerting a serious influence on the water quality, since the characteristics of stormwater runoff is varied by the land usage pattern of an area and a basin, and all sorts of pollutants on the earth in rainfall flow into the urban stream. This study estimated EMC of each pollutant to investigate the characteristics of stormwater runoff by separating the urban area as the housing area and industrial area. As a result of the analysis, the first flush effect occurred in the non-point source pollutant of housing area and industrial area, as the runoff concentration gradually reduces after it rapidly increases in the initial rainfall, and in case of the non-point source pollutant the control of first stage rain-water. It is considered to require the continuous follow-up study such as the scale of long-term rainfall event and water quality data, land usage pattern by GIS method, database of topography and geological features, and so forth.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.2
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• pp.33-40
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• 2017

In Korea, it is required to install the final cover layer immediately after the end of use of the waste landfill, and to conduct aftercare for 30 years. However, the installation of the final cover layer minimizing the penetration of the rainfall will delay the decomposition of the buried organic wastes and reduce the amount of pollutants released into the leachate. Therefore, at the end of the aftercare period, pollutants might be discharged and cause the pollution of the surrounding environment. In this study, using lab-scale lysimeters, the amount of pollutants discharged into the leachate was observed. At the initial stage, same artificial rainfall was injected, and after 7 months later, different reduced artificial rainfall was injected for 8.4 months assuming as the final soil layer was installed. From the results, it was advantageous in terms of environmental management after the end of the aftercare period to install a temporary cover layer that permits the infiltration of rainfall to some extent rather than to install the final cover layer immediately after the end of use of the waste landfill.

• Journal of Environmental Science International
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• v.19 no.6
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• pp.665-670
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• 2010

Pollutants from urban pavement consists various kinds of substances which are originated from dry deposition, a grind out tire, corrosive action of rain to pavement and facilities and raw materials of the road etc.. These are major pollutants of urban NPS (Non-point source) during rainfall period. However there is not enough information to control such pollutants for appropriate management of natural water quality. In this study of transportation areas, three monitoring stations were set up at trunk road, urban highway and national road in Gyeongnam province. Runoff flow rate was measured at every 15minutes by automatic flow meters installed at the end of storm sewer pipe within the road catchment area for water quality analysis. Data was collected every 15 minutes for initial two hours of rainfall. Additional samples were collected 1-4 hours interval till the end of rainfall. The monitoring parameters were $COD_{Mn}$, SS, T-N & T-P and heavy metals. The average EMCs of TSS and $COD_{Mn}$ were 62.0 mg/L and 24.2 mg/L on the city trunk road, which were higher than those of urban highway and national road, indicating higher pollutant loads due to activities in the city downtown area beside the vehicle. On the other hand, the average EMC of T-N and T-P were in the range of 2.67-3.23 mg/L and 0.19-3.21 mg/L for all the sampling sites. Heavy metals from the roads were mainly Fe, Zn, Cu and Mn, showing variable EMCs by the type of road. From the TSS wash-off analysis in terms of FF(first flush) index, first flush phenomenon was clearly observed in the trunk road(FF : 0.89-1.43). However, such mass delivery behavior was not apparently shown in urban highway(FF : 0.90-1.11) and national road(FF : 0.81-1.41).

• Journal of the Korean Geotechnical Society
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• v.22 no.7
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• pp.55-64
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• 2006

Shallow failures of slopes in weathered soils are caused by infiltration caused by prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in suction induced by the water infiltration. In this paper, hysteresis on soil-water characteristic curve (SWCC) of granite and gneiss weathered soils is investigated using transient flow analysis respectively. Each case was subjected to artificial rainfall intensities and time duration depending on the laboratory-based drying and wetting processes. The results show that the unsaturated seepage on weathered slopes are very much affected by the initial suction of soils and unsaturated permeability of the soils. In addition, a granite weathered soil has a lower air-entry value, residual matric suction, and wetting front suction and less hysteresis loop than a gneiss weathered soil.

• Journal of Wetlands Research
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• v.18 no.1
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• pp.24-31
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• 2016

The increase of impervious area in cities caused the unbalanced water cycle system and the accumulated various contaminants, which make troubles as introducing into watershed. In Korea, most of rainfall in a year precipitate in a summer season. This indicate that non-point source pollution control should be more important in summer and careful rainfall reuse strategy is necessary. Accordingly, the aim of this study is to monitor the characteristics of rainfall contaminants harvested in roofs and to develop the rainfall treatment system which are designed to fit well in a typical domestic household including rain garden. The rain garden consists of peatmoss, gravel and san to specially treat the initial rainfall contaminants. For this purpose, lab scale experiments with synthetic rainfall had been conducted to optimize the removal efficiency of TN, TP and CODcr. After lab scale experiments, field scale rainfall treatment system installed as a pilot scale in a field. This system has been monitored during June to July in 2015 in four time rainfall events as investigating the function of time, rainfall, and pollutant concentrations. As results, high loading of pollutants were introduced to the rainfall treatment system and its removal efficiency is increased as increase of pollutant concentrations. Since it is common that the mega-size of rainfall treatment system is not attractive in urban area, small scale rainfall treatment system is promising to treat the non-point source contaminants from cities. In addition, this small scale rainfall treatment system could have a potential to water resue system in islands, which usually suffer the shortage of water.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.350-357
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• 2006

For the purpose of this study, the characteristics of surface flow through the survey of rainfall intensity and degree of slope on fire sites by using rainfall simulator was examined and analysed. And also the relationship between the amount of surface flow and rainfall intensity, degree of slope and elapsed year after forest fire occurrence influencing on the surface flow were analysed. The results obtained were as follows: 1. The amount of surface flow by year of occurrence of forest fire was increased 2,2 to 3,2 times as rainfall intensity was increased by 30 mm/hr, and 1.5 to 1.9 times as degree of slope was increased by $10^{\circ}$, 2, Even though ground vegetation in forest fire sites was recovered more than 80%, the amount of surface flow in initial rainfall was relatively much and it seemed that vegetation didn't play substantial roles in reducing runoff. 3, The amount of surface flow by rainfall intensity and degree of slope in accordance with elapsed years after forest fire was reduced 22,3% to 41,8% in three years after fire as compared to the first year of fire occurrence. The amount of surface flow were significantly differentiated by rainfall intensity and degree of slope in the first year of fire occurrence and the difference were gradually reduced afterwards. 4. In the analysis on influences of each factors on the amount of surface flow on forest fire sites, the amount of surface flow was significant differences in major impacts of each rainfall intensity, degree of slope and elapsed year after fire and interaction of rainfall intensity ${\times}$ degree of slope and rainfall intensity ${\times}$ elapsed year after fire, but no differences were observed in interaction of degree of slope ${\times}$ elapsed year after tire and rainfall intensity ${\times}$ degree of slope ${\times}$ elapsed year after tire. Rainfall intensity was the most affecting factor on the amount of surface flow and followed by degree of slope and elapsed year after fire.