• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.615-624
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• 2004

The distribution pattern of water quality parameters and phytoplankton biomass in upper inflow rivers of lake Paldang had surveyed. In North-Han river system, nutrient concentrations and algal biomass was below the standard of mesoand oligotrophy from lake Soyang to lake Paldang, maintaining good water quality, except the N5 site located near the Chuncheon-Si, showing high nutrients concentrations and algal biomass. The algal biomass of the South-Han river system showed oligotrophic level in the upstream near the lake Chungju, and increased along the flow direction showing eutrophic level in the downstream within the lake Paldang area. On the other hand, the highest concentrations of nutrients were detected in the middle stream near the Yeoju-Si and Yangpyung-Gun rather than in the downstream suggesting algal biomass in lake Paldang would not come from the upper river area but come from the growth within the lake area using nutrients from the upper inflow river.

• Journal of Environmental Science International
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• v.17 no.11
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• pp.1295-1305
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• 2008

This study aims at the analyze of unsteady downstream flow due to dam failure along dam failure scenario and applied to Yeoncheon Dam which was collapsed August 1st 1999, using HEC-RAS simulation model. The boundary conditions of this unsteady flow simulation are that dam failure arrival time could be at 02:45 a.m. August 1st 1999 and failure duration time could be also 30 minutes. Downstream 19.5 km from dam site was simulated for unsteady flow analysis in terms of dam failure and non-failure cases. For the parameter calibration, observed data of Jeonkok station were used and roughness coefficient was applied to simulation model. The result of the peak discharge difference was 2,696 to $1,745\;m^3/sec$ along the downstream between dam failure and non-failure and also peak elevation of water level showed meanly 0.6m difference. Those results of these studies show that dam failure scenarios for the unknown failure time and duration were rational because most results were coincident with observed records. And also those results and procedure could suggest how and when dam failure occurs and downstream unsteady flow analyzes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.11 no.3
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• pp.139-146
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• 1978

The annual variations of some heavy metal concentrations, Al, Mn, Fe, Cu, Pb, Zn, Cd, Hg were determined on tile day of spring tides in every month from May 1977 to April 1978 at eight stations in the Nagdong River downstream. Samples were taken at intervals of one or two hours from 7 a.m. to 7 p.m. at each station. Annual ranges and means of concentrations of the heavy metals are as follows : aluminium 40.7-3700 ppb, 286 ppb; manganese 10.3-261.5 ppb, 80.8 ppb; iron ND-1237 ppb, 147.7 ppb; copper ND-30.9 ppb, 2.49 ppb; lead ND-29.9 ppb, 1.10 ppb; zinc ND-156.8 ppb, 5.61 ppb; cadmium ND-1.22 ppb, 0.09 ppb; mercury ND-0.37 ppb, 0.02 ppb respectively. In general, the contents of heavy metals except managanese and mercury were higher at the stations above station one, Kupo, though the ranges of the contents showed remarkable difference according to the sampling stations. Annual means of the concentrations of iron and manganese were exceeded already the desirable standards for industrial water and closed to the criteria of raw water for public supply. The values that over the criteria of raw water were sometimes found. Mercury concentration showed comparative high level such as ND-0.37 ppb in annual range but it was not over the environment criterion, 0.5 ppb. Aluminium, iron and mercury showed generally high values in summer period and other metals in winter period, through the patterns of seasonal variations were difference depending on the sampling stations and the kind of metals.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.179-186
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• 2007

This paper has investigated a rise of water level in upstream and downstream of bridge, which is caused by accumulation of debris in a bridge. The debris has been classified into several types in terms of size. The rise of water level which has been caused by installation and removal of sheet pile that is used to block water in a bridge has been analyzed using HEC-RAS model. According to the analysis, it has turned out that the debris has no influence on the rise of water level in ordinary water flow. In addition, sheet pile has little impact on the rise of water as well. Even though the impact of sheet file has turned out trivial in flood flow just like the ordinary water flow, it's been simulated that the maximum water level difference between upstream and downstream of bridge turned out more than 1.0meter because of debris in 80-year or more flood frequency. When the rise of water level in upstream from the cross section of the bridge was investigated based on 100-year flood frequency, besides, it has turned out that it had an influence up to 17.84km distance because of the effect of debris.

• Journal of Korea Water Resources Association
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• v.48 no.6
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• pp.501-509
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• 2015

Lately multipurpose dam is required to consider various interests such as quality, ecological environment as well as flood control, water supply, hydropower generation, etc. The objective of this study is to investigation and analysis of water temperature in the areas where there are social conflicts due to cold water outflow. In this study, we monitored water temperature of Juam regulation dam, downstream river, Suncheon bay in a long term period and performed comparative analysis on a change of water temperature in downstream river and Suncheon bay by using three-dimensional numerical mode (EFDC) considering various external factors such as water outflow amount. The result of monitoring and numerical modelling indicates that effects of cold water outflow takes place from april to september. Also effects of the low temperature discharge of dam was complicatedly altered by various factors such as outflow time and amount, weather and tide level conditions etc. The result of this study can be utilized as a basic data for establishing improvement of dam operation plan to minimize negative effects of dam's cold temperature water outflow to downstream river and coastal area.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.3 s.14
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• pp.51-60
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• 2004

Urban flood damage has been caused by drainage deficiency. One of the methods to solve this problem is to construct detention basin and Pumping station and to pump out the water to the river. However, because of rapid urbanization, the capacity of drainage pipelines is sometimes not sufficient enough during the rainy season. Therefore, even though we have enough pumping stations, the inflow of surface water never reaches to the detention area, causing floods in urban area. This research is to find improvement of urban drainage system, estimating drainage pipeline risk. Also, eight models for a computer program were developed for practical use. The models were verified changing precipitation duration, intensity, design period, time distribution model, and etc. This verification was processed focusing that the model can regulate the water level in the detention basin and minimize the effect downstream. As a result Fuzzy models were found to be efficient to lower the water level in detention basin, and decreased about 8 cm in water level of downstream.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.149-157
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• 2000

This paper presents the first results of dissolved arsenic in the Kangnung Namdae stream. The distribution of As concentrations measured in 28 August (high water flow) and in 21 November 1997 (low water flow) differs from those of other metals measured during the same period; The concentrations of Doam-dam are lower than those of Obong-dam and accumulation in the downstream in the period of low water flow is not pronounced. The As concentration in the downstream under the low water flow is lower than under high water flow, reciprocally to other metals. Freshwater concentrations are comparable with those measured in pristine river and lower than the world average and the diffrence of concentrations measured during two period is minute. Therefore, the As concentrations in the Namdae stream are background level and the source of As contamination does not exist. In the mixing zone between the freshwater and Donghae seawater, As behave conservatively, indicating the absence of any significant removal or mobilization processes. A first estimation of total dissolved As input from Namdae stream to Donghae coastal sea shows 65.12 kg/yr.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6B
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• pp.533-540
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• 2010

Recently management of vegetation distributed in the watercourse is very important not only for safety but also for river restoration. In general, vegetations in the watercourse increase hydraulic resistance and accordingly decrease conveyance capacity which may yield levee overflow. This paper simulates water level rise using 1D and 2D hydro dynamic model to check the possibility of overflow in downstream of the Soyang Reservoir by assigning different roughness coefficient corresponding to different types of vegetation. In this study, 3 different vegetation types of tree, shrub, and main channel were considered and corresponding Manning's roughness coefficient n was assigned based on the vegetation map generated from the site investigation. As results, the water level raised about 0.1 to 0.7 m comparing with the case without considering vegetation and a proper measurements is necessary where overflow occurs due to low level levee.

• KDI Journal of Economic Policy
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• v.44 no.4
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• pp.1-24
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• 2022

We investigate how reforestation contributed to stabilization of riverine water levels in South Korea. For the purpose, we estimate an equation capturing dynamic relationships among rainfall, upstream-area tree stock, and downstream water levels in three river systems of Hongcheon, Mangyeong, and Hyeongsan, using daily observations of precipitation and water levels for the period from 1985 to 2005. Simulation based on estimation results shows that increase in the tree stock in a river basin leads to a significantly suppressed peaking in riverine water levels in response to an abrupt and concentrated rain in the upstream area. For instance, an hour-long concentration of 100mm rain results in 0.7m rise in water level if the volume of growing stock is 1 million m³, whereas the rise in water level stays below 0.27m with 5 million m³ in the growing-stock volume.

• Journal of Korea Water Resources Association
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• v.52 no.6
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• pp.397-409
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• 2019

Gate operation of hydraulic structures is important for proper management in rivers. In this study, the characteristics of flood time were analyzed and predicted using the HEC-RAS model, which is capable of one-dimensional and two-dimensional connectivity analysis of the main points downstream of the Geum river. As a result, flood travel time was decreased once discharge increase and downstream water level rising. However, When the floodplain was overflowed, the arrival time increased due to the rapid increase of the river width. Also, the same condition, flood wave travel time at the major point was approximately twice as fast as water level rising travel time, indicating that waves progressed faster than actually water. Using the results of this study, it will be helpful in the river.