• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.903-913
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• 2021

In the flood season, the measurement of the river discharge has many restrictions due to reasons such as budget, manpower, safety, convenience in measurement and so on. In particular, when heavy rain events occur due to typhoons, etc., it is difficult to measure the amount of flood due to the above problems. In order to improve this problem, in this study, a method was developed that can measure the river discharge in a flood season simply and safely in a short time with minimal manpower by combining the functions of a drone and a surface velocity doppler radar. To overcome the mechanical limitations of drones caused by weather issues such as wind and rainfall derived from the measurement of the river discharge using the conventional drone, we developed a drone with P56 grade dustproof and waterproof performance, stable flight capability at a wind speed of up to 36 km/h, and a payload weight of up to 10 kg. Further, to eliminate vibration which is the most important constraint factor in the measurement with a surface velocity doppler radar, a damper plate was developed as a device that combines a drone and a surface velocity Doppler radar. The velocity meter DSVM (Dron and Surface Veloctity Meter using doppler radar) that combines the flight equipment with the velocity meter was produced. The error of ±3.5% occurred as a result of measuring the river discharge using DSVM at the point of Geumsan-gun (Hwangpunggyo) located at Bonghwang stream (the first tributary stream of the Geum River). In addition, when calculating the mean velocity from the measured surface velocity, the measurement was performed using ADCP simultaneously to improve accuracy, and the mean velocity conversion factor (0.92) was calculated by comparing the mean velocity. In this study, the discharge measured by combining a drone and a surface velocity meter was compared with the discharge measured using ADCP and floats, so that the application and utility of DSVM was confirmed.

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.497-509
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• 2019

After the Total Maximum Daily Loads(TMDLs) was applied, it became beyond the limit of concentration management. However, it does not adequately reflect the characteristics of various watersheds, and causes problems with local governments because of the standard flow set. Thus, in this study, the Han River system is organized into four groups in estimating the Pollution Contribution by applying the Flow Duration Curve(FDC) created by the daily flow of data from the HSPF. And the method of this study is expected to be valuable as basic data for the TMDLs. As a result, Group I contains the main watersheds with no large hydraulic structures and tributary watersheds. There is no specificity in the FDC and the Pollution Contribution is estimated as rainfall runoff. Group II contains watersheds near the city where the FDC is maintained above a certain level during the Low Flow Conditions and the Pollution Contribution is estimated as the discharge flow of large scale point pollution facilities. Group III contains the main watersheds in which the large hydraulic structures are installed and FDC is curved in the Low Flow Conditions. So the Pollution Contribution is estimated as the water quality of the large hydraulic structures. Group IV contains the upstream in mainstream watersheds in which the large hydraulic structures are installed and the FDC is disabled before the Low Flow Conditions. As the flow is concentrated in the High Flow Conditions, the non-point pollution sources are estimated as the Pollution Contribution.

• Journal of Korea Water Resources Association
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• v.37 no.7
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• pp.599-612
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• 2004

The continuous long-term rainfall-runoff simulation model SWAT has the advantage of being able to account for various land use, however, SWAT lacks the capability of simulating the drainage characteristics of urban area. On the other hand, SWMM, which is the most popular model for runoff analysis of urban watershed, has the advantage of being capable of considering surface and drainage characteristics in urban area, but SWMM cannot easily account for land use other than urban area within a watershed. In this study, SWAT-SWMM model, which builds on the strengths of SWAT and SWMM, has been applied to the Osan River Watershed which is a tributary watershed to the Gyung-Ahn River. From the application, the results from coupled SWAT-SWMM model has been compared to the ones from SWAT for each hydrologic component such as evapotranspiration, surface runoff, groundwater flow, and watershed and channel discharge, and the runoff characteristics of two models for each hydrologic component has been discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.8
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• pp.3594-3602
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• 2011

The purpose of this study is complementing existing flood-reaching timetable by theoretically determined numerical model and suggesting techniques for calculating the exact arrival time of flood. For this, according to the discharge of Namhan River, arrival time measurements, using u-IT technology applied sensor buoys, were performed. Based on the results of measurements, this study proposed complementary relation of average reach time by the discharged water considering tributary inflow, which was not considered established expression. With this study, u-IT based actual technology that is complementing the existing flood forcasting-warning data was developed. Applying this technology to the average reach time calculation by the discharged water, it is expected to reduce flood-oriented damage.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.15-22
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• 2009

This study reports the serial use of a 3-D hydrodynamic model, EFDC-Hydro and a dynamic water quality model WASP7.2 that are maintained by USEPA. The 48 km section of the Geum River downstream between Daechung Dam and Gongju was selected as a sample study site. Topographical information was used to accurately represent morphology of the study site and boundary conditions were derived from governmental databases including WAMIS by Ministry of Land and Ocean and WEIS by Ministry of Environment. EFDC-Hydro was successfully calibrated for observed water level and WASP was calibrated using monthly observed water quality data obtained from the above sources. It was found that the current water quality target of BOD for the Geum River-H point could not be met on monthly basis though every other tributary of the area would meet its own water quality target as assigned in Korean TMDL. This study proposed the new target BOD water quality for the Gabcheon and Mihocheon as 4.3 and 3.6 mg/l, respectively so that the Geum River-H point can meet the target. When Sejong City is constructed, it is estimated that effluent discharge limit of BOD must be less than 4.5 mg/l to meet water quality of the point. This study shows that it is possible to carry out more precise modeling considering both water movement and water kinetics by using EFDC and WASP simultaneously.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.2
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• pp.36-52
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• 2020

This study performed 2-D(two-dimensional) hydrodynamic analysis using EFDC in the Nakdong River. For the simulation of the flood season and non-flood season, the measured data including water level, weir outflow and tributary inflow were used, and the accuracy and applicability of the model were verified by comparing the measured water level and computed one. In addition, statistical quantitative assessment of the model performance was performed by estimating PBIAS, RSR, and RMSE for the computed water level. Then, the average velocity for each section between weirs was calculated by applying constant discharge conditions, and it was compared and verified with the measured velocity by Hydrological Survey Center. In this study, a simple method for estimating the arrival time was proposed, and it is expected that it will be practically applicable in field practices such as flood forecasting and warning.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.294-301
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• 2016

The underflow type movable weirs were arranged in a multi-stage way at a section of the Chiseong River, a tributary of Geum River, where flooding is observed frequently. The flood control and the movable weir management levels were compared with the occasions of installing the existing weir for analysis. The peak discharge decreased by a maximum of 97% for the underflow type movable weir, and the downstream flood elevation decreased by a maximum of 82%. The amount of storage also increased by a maximum of 463% by the distribution and storage functions of the multi-stage arrangement of the underflow type movable weirs. It is possible to suggest that the management level of each movable weir for the target storage of the reach and the flood reduction level through the relationship among this storage, downstream peak flood elevation, and peak flow.

• Journal of Korea Water Resources Association
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• v.47 no.3
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• pp.269-283
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• 2014

This study evaluated the environmental impact based on watershed characteristics and climate change using RCP climate change scenarios provided by the Korea Meteorological Administration. Future dam inflow was estimated by the SWAT model. Dam safety evaluation and downstream duration curve analysis was performed using HEC-ResSim model. Trends of water quality was analyzed through seasonal-Kendall Test using existing water quality observation data. Release discharge and tributary runoff derived SWAT and HEC-ResSim models applied to Qual2E and the future change in water quality trends were analyzed. Integrated environmental review watershed following techniques will be able to obtain the river environment management system and environmental issues such as climate change, new guidelines for preemptively response will be provided.

• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.969-976
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• 2006

The purpose of this study is to trace the flood inundation area around rural small stream by using RADARSAT image because it has the ability of acquiring data during storm period irrespective of rain and cloud. For the storm August 9, 1998 in the Anseong-cheon watershed, three RADARSAT images before, just after and after the storm were used. After ortho-rectification using 5 m DEM, two methods of RGB composition and ratio were tried and found the inundated area in the tributary stream, the Seonghwan-cheon and the Hakjeong-cheon. The inundated area had occurred at the joint area of two streams, thus the floodwater overflowed bounding discharge capacity of the stream. The progression of damage areas were stopped by the local road and farm road along the paddy. The result can be used to acquire the flood inundation data scattered as a small scale in rural area.

• Journal of Korea Water Resources Association
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• v.44 no.6
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• pp.439-447
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• 2011

This study aims to test the feasibility of combined use of EFDC (Environmental Fluid Dynamics Code) hydrodynamic model and WASP7.3 (Water Quality Analysis Program) model to improve accuracy of water quality predictions of the Yongdam Lake, Korea. The orthogonal curvilinear grid system was used for EFDC model to represent riverine shape of the study area. Relationship between volume, surface and elevation results were checked to verify if the grid system represents morphology of the lake properly. Monthly average boundary water quality conditions were estimated using the monthly monitored water quality data from Korean Ministry of Environment DB system. Monthly tributary flow rates were back-routed using dam discharge data and allocated in proportion to each basin area as direct measurements were not available. The optimum number of grid system was determined to be 372 horizontal cells and 10 vertical layers of the site for 1 year simulation of hydrodynamics and water quality out of iterative trials. Monthly observed BOD, TN, TP and Chl-a concentrations inside the lake were used for calibration of WASP7.3 model. This study shows that EFDC and WASP can be used in series successfully to improve accuracy in water quality modeling. However, it was observed that the amount of data to develop inflow water quality and flow rate boundary conditions and water quality data inside lake for calibration were not enough for accurate modeling. It is suggested that object-oriented data collection systems would be necessary to ensure accuracy of EFDC-WASP model application and thus for efficient lake water quality management strategy development.