• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1737-1741
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• 2007

Using kinematic wave equation, the influence of moving rainstorms to runoff was analysised with a focus on watershed shapes and rainfall distribution types. Watershed shapes used are the oblong, square and elongated shape, and the distribution types of moving storms used are uniform, advanced and intermediate type. The runoff hydrographs according to the rainfall distribution types were simulated and the characteristics were explored for the storms moving down, up and cross the watershed with various velocity. And the hydrographs were compared in the case of varing the rainstorm intensity and varing the rainstorm length in order to make the same total runoff volume. When the rainstorm intensity was varied the shape, peak time and peak runoff of a runoff hydrograph are significantly influenced by spatial and temporal variability in rainfall and watershed shapes. The peak time of down and upstream moving strorms appeared latest in the case of the elongated shape basin, meanwhile at cross stream moving storms, the peak time of elongated shape basin is earlier than the others. For storms moving downstream peak time was more delayed than for other storm direction in the case of elongated watershed. The runoff volume and time base of the hydrograph decreased with the increasing storm speed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.1
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• pp.40-50
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• 2011

We study the characteristic and total flux of non-point pollutants such as total suspended solids (TSS), chemical oxygen demand (COD), dissolved nutrients, total phosphorus (TP) and total nitrogen (TN) in the storm water runoff from urban streams and sewer outlets of Banweol Industrial Complex around Shihwa Lake. The concentrations of non-point pollutants were generally increased with increasing of the duration and intensity of rainfall. Mean TSS concentration of Ansan stream was higher than that of sewer outlets but mean concentrations of COD, TP and TN were approximately 2~5 times higher of sewer outlet than of urban stream. TSS showed statistically positive relationships with COD and TP but it had negative correlation with dissolved nutrients. There was a significant correlation between total flux of non-point pollutants in the storm water runoff and total basin area of each sewer outlet, showing that the highest runoff flux was observed at 3rd sewer outlet which represents the largest basin area from Banweol industrial complex. Total runoff fluxes for TSS, COD, TP and TN in this study were 187,536 kg, 17,118 kg, 922 kg, 13,519 kg, respectively. Given the basin area of sewer outlet in Banweol industrial complex which corresponds only 3% from total catchment area around Shihwa Lake, enormous amount of non-point pollutants will be entered into Shihwa Lake without any treatment. It is necessary to manage and reduce of various non-point sources and pollutants because the runoff of nonpoint pollutants during storm events should be deteriorating the water quality of Shihwa Lake. Our results provides useful informations on the development of best managements practices (BMPs) for effective implementation of total pollution loads management system of Shihwa Lake.

• Water for future
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• v.26 no.2
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• pp.49-57
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• 1993

A hydrological method is performed to determine the critical duration of design rainfall for the design of storm sewer in Seoul. To seize the effect of the duration and the temporal distribution of the rainfall to the peak discharge of the storm sewer, the Huff's quartile method is used as a temporal pattern for the design rainfall of any durations (9 cases for 20-240 min.) with 10 years return period. The critical duration of design rainfall is determined as the duration which maximizes the peak discharge. This study is applied to 18 urban drainage systems in Seoul. The ILLUDAS model is applied to runoff analysis, and the result shows that the duration which maximizes peak discharge is 30, 60 minutes generally. The relation diagram between peak discharge for the critical duration and watershed area is prepared for the design of storm sewer.

• Spatial Information Research
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• v.15 no.2
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• pp.159-167
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• 2007

In this study, we investigated the application of extending the Huff's method to design discharge being used at present up to the event of concentrated rainfall. As our field study site, we selected Odae Cheon basin in Pheongchang, which was affected by concentrated rainfall in July 2006. Actual concentrated rainfall and design rainfall derived from the Huff's method were used to calculate the discharge and storm water levels, which were compared with the directly measured water-level marks of storm discharges. The results showed that the peak storm discharge from the torrential rainfall was twice higher than the design rainfall. The short term discharges from concentrated rainfall closely corresponded to the rainfall discharges of 150 years storm frequency.

• Journal of Wetlands Research
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• v.19 no.4
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• pp.515-522
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• 2017

This study investigated the runoff characteristics containing NPS pollutants in urban areas and estimated the optimal number of storm events to be monitored. 13 residential areas, 8 commercial areas, 9 transportation areas and 11 industrial areas were selected to be monitored located in urban areas. Monitoring was performed from 2008 to 2016 with a total of 632 rainfall events. As a result, it was found that commercial area needs priority NPS management compared to other landuses because the commercial area has high runoff coefficient and NPS pollutant EMC compared with other landuses. The annual monitoring frequency for each landuse was estimated to be 11 to 14 times for industrial area, 12 to 14 times for transportation area, 11 to 13 times for commercial area and 22 to 25 times for residential area. Even with the use of accumulated monitoring data for several years, there is still high probability of uncertainty due to high error in some pollutant items, and it is necessary to establish monitoring know-how and data accumulation to reduce errors by continuous monitoring.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.205-212
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• 2004

Phosphorus cycle was studied in a deep stratified reservoir in summer monsoon area (Lake Soyang, Korea) by surveying phosphorus input from the watershed and the movement of phosphorus within the reservoir. And the spatial and temporal distribution of phosphorus was modeled with a 2-dimensional water quality model (CE-QUAL-W2), Phosphorus loading was calculated by measuring TP in the main inflowing river (the Soyang River) accounting for 90% of watershed discharge. TP of the Soyang River showed a large daily variation with the flow rate. High phosphorus loading occurred during a few episodic storm runoff laden with suspended sediments and phosphorus. Because storm runoff water on rainy days have lower temperature, it plunges into a depth of same temperature (usually below 20m depth), forming an intermediate turbidity layer with a thickness of 20 ${\sim}$ 30 m. Because of stable thermal stratification in summer the intermediate layer water of high phosphorus content was discharged from the dam through a mid-depth outlet without diffusing into epilimnion. The movement of runoff water within the reservoir, and the subsequent distribution of phosphorus were well simulated by the water quality model showing a good accuracy. The major parameter for the calibration of phosphorus cycle was a settling velocity of detritus, which was calibrated to be 0.75 m ${\cdot}$ $day^{-1}$. It is concluded that the model can be a good simulator of limnological phenomena in reservoirs of summer monsoon area.

• Water for future
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• v.8 no.1
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• pp.61-79
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• 1975

An attempt is made to develope a scheme for synthesizing unit hydrograph for any arbitrary small watershed in the Han or Geum River basin, which can be applied in determining various sizes of design flood for flood control prijects. Stage gauging stations, seven in the Han and five in the Geun River basin with rating curves, were selected as subbasins for the analysis. Unit hydrographs of 2-hour duration were derived for several heavy storm events using the storm and the corresponding flood runoff data for each subbasin. The Clark method programmed by the Hydrologic Engineering Center, U.S. Corps of Engineers, was utilized for derivation of instantaneous unit hydrographs which were, in turn, converted into 2-hour unit hydrograph. By averaging the 2-hour unit hydrographs from several storm events a representative 2-hour unit hydrograph was determined for each subbasin and hence a separate derivation of dimensionless unit hedrograph was also possible for the Han and Geum River basins. The physiographic characteristics such as stream length, distance to the centroid of each watershed were correlated with the characteristic parameters of the derived unit hydrograph for the subbasins within two large basins. correlation analyses between the characteristic parameters were also made. These correlation analyses resulted a series of four equations and a dimensionless unit hydrograph for the two large basins, which made it possible to draw a synthetic 2-hour unitgraph for any small watershed within the Han or Geum River basin. A detailed procedure for aplying the derived method for an arbitrary basin is summarized with one sample computation for each of the two basins. A comparison of the actually derived 2-hour unit hydrogrograph and the synthesized one showed a fair agreement. A recommendation is made for the further study.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.7
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• pp.483-490
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• 2009

The aims of this study were to evaluate the removal efficiency for various pollutants in urban storm runoff by a filtration device, and to determine design parameters depending on filter media properties. Appropriate selection of filter media will affect the size and life time of the filtration device. Sets of column tests were performed in order to evaluate the removal efficiency by perlite and a synthetic resin. An investigation of surface properties including CEC (cation exchange capacity) and zeta-potential suggested that the perlite had a superior adsorption capability for cationic pollutants. TCODcr and turbidity were analyzed to investigate the removal characteristic of particulate pollutant. In both columns, the particles in the collected storm runoff was almost completely capture with a small EBCT (empty bed contact time) of 2.5 minutes. Complete clogging at the EBCT of 2.5 minutes occurred after 630 minutes in the perlite column and 810 minutes in the resin column. The removal efficiency of TCODcr and turbidity at the EBCT of 2.5 minutes decreased to below 70% due to an wall effect. The removal efficiency for dissolved pollutant (SCODcr) was negligible due to the insufficient contact time for adsorption. The removal of heavy metals (Cu, Zn, Pb) was mostly ascribed to the filtration of particles containing metals, since the relationship between CEC and the removal efficiency was not apparent. The result of this study would be valuable for the application of filtration device to control of urban storm runoff.

• Journal of Korean Society on Water Environment
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• v.26 no.3
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• pp.432-438
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• 2010

LIDMOD2 was developed for evaluation of low impact development (LID) and best management practice (BMP) by modification of Site Evaluation Tool (SET). The modification includes employment of SCS-CN method for annual runoff simulation, unit load method for annual pollutant loads simulation, and the method proposed by Korean TMDL for calculating pollutant reduction by BMPs. The CN values were updated with regionalized parameters within Nack-Dong River basin because these are important parameters for simulating hydrology. LIDMOD2 was tested by applying to Andong Bus terminal. As a simulation results, pollutant loads and surface runoff will be significantly increased by post-development without LID compared with those from pre-development. LID technique was simulated to efficiently reduce surface runoff and pollutant load and increase infiltration. LIDMOD2 is screening level tool and easy to use because LIDMOD2 is based on spread sheet and most of parameters are regionalized. LIDMOD2 was illustrate that it could evaluate LID well by summarizing and graphing annual hydrology, annual pollutant loading, and hydrograph for event storm. The calculation methods related with pollutant loads are employed from the guideline of Korean TMDL and it can be useful tool for Korean TMDL to evaluate the effect of LID/BMP on developing area.

• Journal of Forest and Environmental Science
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• v.34 no.4
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• pp.293-303
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• 2018

Sumber Jaya (54,194 hectares) is a district in West Lampung, Indonesia, located at the upper part of Tulang Bawang watershed. This watershed is one major water resource for Lampung Province, but has become a focal point of discussion because of the widespread conversion of forestland to coffee plantations and human settlements which lead to environmental and hydrological problems. This research aimed to evaluate Sumber Jaya watershed affecting by rapid land use change using hydrological methods as a base for watershed management. Nested catchment structure consisted of eight sub-catchments was employed in this research to assess scaling issues of land use change impacts on rainfall-runoff connections. Six tipping bucket rain gages were installed on the hill slopes of each sub-catchment and Parshall flumes were installed at the outlets of each sub-catchment to monitor stream flow. First, unit hydrograph that expressed the relationship of rainfall and runoff was computed using IHACRES model. Second, unit hydrograph was also constructed from observations of input and response during several significant storms with approximately equal duration. The result showed that most of the storm flow from these catchments consisted of slow flow. A maximum of about 50% of the effective rainfall became quick flow, and only less than 10% of remaining effective rainfall which was routed as slow flow contributed to hydrograph peaks; the rest was stored. Also, comparing peak responses and recession rates on the hydrograph, storm flow discharge was generally increased slowly on the rising limb and decreased rapidly on the falling limb. These responses indicated the soils in these catchments were still able to hold and store rain water.