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

• Journal of The Korean Society of Agricultural Engineers
• /
• v.60 no.3
• /
• pp.95-105
• /
• 2018

Understanding the composition of the dam inflow can improve the efficiency of dam operation considering the seasonal characteristics. Hydrograph analysis is one of the methods to identify the characteristics of dam inflow. In addition, baseflow separation on the dam inflow can be affected by anthropogenic influences depending on dam locations. In this regard, the objectives of this study are 1) to analyze yearly and monthly baseflow contribution to the dam inflow and 2) to compare the baseflow contribution to the inflow in dams located upstream and downstream of the watershed. The result shows that the estimated baseflow index was smaller in the upstream dams compared to the downstream dams. Discharge from the upstream water infrastructure including dams and reservoirs can be a part of inflow into the downstream water infrastructure. Based on this scenario, the discharge regulated from the upstream dam could lead to overestimation of baseflow contribution to inflow into the downstream dam. We expect that the results from this study elucidate the role and function of dams and hence, contribute to the efficient operation of dams located in the upstream and the downstream of the watershed.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.1403-1407
• /
• 2005

In order to analyze the water storage of the Daecheong dam after constructing the Yongdam dam situated in upstream, a daily cascaded simulation model for analyzing water storages in the Yongdam-Daecheong dams was developed. Operation scenarios of the Yongdam dam were selected to 8 cases with the combinations of downstream outflows and water supplies to the Jeonju region. Daily water storages in the Daecheong dam was analyzed daily by simulating from 1983 to 2004. The results are summarized as follows. Firstly, water supplies from the Daecheong dam were analyzed to amount $1,964.2Mm^3$ on a yearly average in case without the Yongdam dam. In case with the Yongdam dam, water supplies from the Daecheong dam were analyzed to amount $1,858.7\~1,927.3Mm^3$ in case with downstream outflow of $5\;m^3$ is, and were analyzed to amount $1,994.9\~2,017.8Mm^3$ in case with downstream outflow of $10\;m^3/s $. These values are compared to $1,649Mm^3$ applied in design. Secondly, reservoir use rate which was defined rate of water supply to effective water storage reached $241.3\% in case without the Yongdam dam. In case with the Yongdam dam, reservoir use rate reached $228.3\~236.8\% In case with downstream outflow of $5\;m^3/s$, and reached $245.1\~247.9\% in case with downstream outflow of $10\;m^3/s$. Thirdly, runoff rate which is defined rate of dam inflow to areal rainfall reached $57.3\% in case without the Yongdam dam. In case with the Yongdam dam, reservoir use rate reached $62.0\~68.4\% in case with downstream outflow of $5\;m^3/s$, and reached $64.1\~68.5\% in case with downstream outflow of $10\;m^3/s$. Fourth, in case with downstream outflow of $10\;m^3/s$ is from the Yongdam dam, appropriate water supply amounts to the Jeonju region were analyzed to only $0.50Mm^3/day$ from the daily simulation of water storages in the Yongdam dam. Comprehensively, water supply capacity of the Daecheong dam was analyzed to affect in small amounts in spite of the construction of the Yonsdam dam. It is effected to achieve the effective water management of the Yongdam dam and the Daecheong dam by using the developed cascaded model.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1666-1670
• /
• 2006

The purpose of this study is to analyze how a downstream channel is affected in case of hypothetical dam failure. The object of it is Hwacheon dam basin within the basin of North Han river. This study has analyzed the influence on Pyeonghwa(Peace) dam and Hwacheon dam supposing that the Imnam dam in North Korea on the upper stream of North Han river is failed hypothetically at the MFWL(maximum flood water level) by a deluge of rain. The model applied at the main study is NWS(National Weather Service) FLDWAV(Flood Wave Routing Model). Dam breach characteristics data are analyzed by making nine hypothetical scenarios on the basis of other studies on the shape and size of dam breach, time of failure and so on. Expected peak discharge through the breach is verified to have the propriety in comparison with empirical function which is developed on the basis of the case of dam breach in the foreign countries and it is observed that peak discharge is more increasing, as the time of breach gets shorter and the breach width gets bigger. As a result of main study, even though the Imnam dam is hypothetically failed down, there has no influence on the Hwacheon dam of the downstream as the extended Pyeonghwa dam on the downstream controls the volume of discharge properly.

• Korean Journal of Agricultural Science
• /
• v.50 no.3
• /
• pp.331-347
• /
• 2023

The downstream submergence damages caused during the flood season in 2020, around the Yongdam-dam and five other sites, were analyzed using related dam management data. Hourly- and daily-data were collected from public national websites and to conduct various analyses, such as autocorrelation, partial-correlation, stationary test, trend test, Granger causality, Rescaled analysis, and principal statistical analysis, to find the cause of the catastrophic damages in 2020. The damage surrounding the Yongdam-dam in 2020 was confirmed to be caused by mis-management of the flood season water level. A similar pattern was found downstream of the Namgang- and Hapcheon-dams, however the damage caused via discharges from these dams in same year is uncertain. Conversely, a different pattern from that of the Yongdam-dam was seen in the areas downstream of Sumjingang- and Daecheongdams, in which the management of the flood season water level appeared appropriate and hence, the damages is assumed to have occurred via the increase in the absolute discharge amount from the dams and flood control capacity leakage of the downstream river. Because of the non-stationarity of the management data, we adapted the wavelet transform analysis to observe the behaviors of the dam management data in detail. Based on the results, an increasing trend in the discharge amount was observed from the dams after the year 2000, which may serve as a warning about similar trends in the future. Therefore, additional and continuous research on downstream safety against dam discharges is necessary.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.11 no.3
• /
• pp.74-86
• /
• 2008

To assessment the disturbances of the Namgang caused by dam construction, upstream area was selected for the reference reach and downstream area was selected for the comparison reach. And these reaches were surveyed and analyzed according to the assessment criteria of the river disturbances.The artificial factors of river disturbances were classified as river improvement works, dam construction and aggregate dredging. The indexes were physical factors as like epifaunal (bottom), embeddedness, velocity/depth regime, sediment deposition, channel flow status, channel alteration, frequency of riffles, bank stability, vegetative protection, riparian zone etc.The assessment results showed 46% of the assessment criteria which was serious status in dam downstream area and 89.5% of it which was excellent status in dam upstream.Finally, the results showed that physical river environment in downstream area was disturbed by the discharge control and the interception of sediment discharge by dam, consequently this disturbance give rise to impact of ecosystem in river.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.1
• /
• pp.103-108
• /
• 2008

Riverbed change is greatly influenced by artificial factors such as dam construction, gravel collection, and river improvement. This study simulated a long-term bed change based on the GSTARS3 model using actual data from the area downstream of the Geum River Daecheong Dam and compared the estimation with a section of the actual measurement. As a result, it was found that the section of the actual measurement was far lower than the result of the simulation in terms of long-term bed change. While the area downstream of Daecheong Dam displayed approximately an average of 2.29 m of streambed degradation on average while the upper stream area showed approximately 0.63 m of bed degradation over 24 years. In the simulation of the area downstream of Daecheong Dam based on the GSTARS3 model, similar bed degradation was observed. However, a great difference was detected between the result and the actual measurement. According to the cause analysis, the riverbed in the area downstream of Daecheong Dam has continuously degraded due to the dam construction and mass collection of gravel. The mass collection of gravel was the main cause of riverbed change. It was found that about 76% of all riverbed degradation was caused by the mass collection of gravel.

• Journal of the Korean Society of Safety
• /
• v.27 no.6
• /
• pp.166-171
• /
• 2012

This study aims to analyze the hydrological characteristics of downstream areas by the dam discharge of Soyanggang dam by using HEC-RAS Model. As a result of analyzing the data of dam discharge divided into hydropeaking discharge and total discharge, it as found that the maximum hydro-peaking discharge and the maximum total discharge have been 254.4 CMS and 1567.7 CMS respectively for the past 11 years. When the hydro-peaking discharge was applied to HEC-RAS Model, there occurred some sections where the water level rapidly changed, but the velocity of moving water was quite stable in the range between 0.23 m/sec and 1.16m/sec. Besides, when the total discharge was applied to this model, the submersible bridge along the dam downstream was flooded, and in some sections, the water level increased over the flood plain. Accordingly, this study judged that it is required to necessarily consider all the influence made by an increase of Soyanggang Dam's discharge when waterfronts are installed or used at dam downstream areas.

• Journal of The Geomorphological Association of Korea
• /
• v.28 no.2
• /
• pp.1-13
• /
• 2021

It is very important to secure sufficient river maintenance flow for the ecosystem, since the ecosystem in the downstream section of the dam is greatly affected by the stream maintenance flow from the dam. However, the amount of discharge from the Seomjingang Dam is decreasing year by year, this study estimated the ecological flow required for the downstream section of the Seomjingang Dam, which is known as the habitat of the endangered Acheilognathus somjinensis, in order to secure the river flow of the Seomjingang Dam. For this purpose, the proper discharge was calculated using the PHABSIM model, which is a hydrological survey and physical habitat simulation method, and the proper discharge of other fish species were also comprehensively reviewed. As a result of this study, the current river maintenance flow at the Seomjingang Dam partially satisfies the ecological maintenance flow including the Acheilognathus somjinensis in the downstream section of the Seomjingang Dam. However, this is recognized as the minimum discharge to maintain the ecology in the downstream section of the Seomjingang Dam, and it would be more desirable to secure larger river maintenance flow than this. This study can contribute the determination of the river maintenance flow of the Seomjingang Dam by proposing the river maintenance flow considering the fish habitat environment in the river.

• Journal of Environmental Science International
• /
• v.23 no.5
• /
• pp.807-817
• /
• 2014

Benthic macroinvertebrates were seasonally sampled from upstream and downstream of the Gunwi Dam construction site from 2006 to 2012. Totally 148 and 165 species were collected at the upstream and downstream sampling sites, respectively. At the upstream area after dam construction, there was no significant change of the numbers of non-insect taxa, but at the downstream area, the non-insect taxon numbers were increased gradually. The individual ratio of Ephemeroptera and Diptera had higher value than the other taxa in both of up and downstream. The trichopteran individual ratios were increased in upstream sites, but decreased in downstream sites from 2010. Also, non-insects and coleopteran individual ratios were decreased in upstream, but increased in downstream after completion of dam construction. The annual range of fluctuation in community indices narrowed after construction. According to a functional feeding group analysis, the individual ratios of FC (Filtering Collector) were increased, and GC (Gathering Collector) and SC (Scraper) were decreased in upstream sites annually. In contrast, the annual individual ratios of FC were decreased, and GC and SC were increased in the downstream sites.