• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.551-560
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• 2001

The research estimated the roughness coefficients for the reach of Hwawon-Goryeonggyo-Hyeongpung stage stations in the Nakdong River through hydraulic channel routing. The data needed were only stage data from the three stations and river cross section data. Stage-discharge relations were determined from the computed discharges by the channel routing. They are better than the previous stage-discharge relations from direct measurements. Discharge computation errors from stage errors were analyzed and a simple method was suggested to limt reach lengths from prohibiting large errors from lateral inflows.

• Journal of Environmental Science International
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• v.22 no.2
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• pp.195-203
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• 2013

I investigated the river morphology and river naturality according to the environment of the Hwang River. The numbers of flexions at the upstream regions were more than those of downstream regions. The Hwang River showed very low overall diversity of the flow. Materials of river shore at low channel width were mainly boulders or gravel at the upstream regions, and the middle and downstream were silts and clay. Artificial masonry and natural materials were mixed from materials of river levees. The Hwang River was some of the natural herbaceous vegetation to riparian zones. Land utilities for floodplain were extremely overall farmland were predominant, and partly used by natural vegetation in the forest, a soccer field, some park facilities, residential, and commercial facilities. The water was width sleep / rivers beam ratio of 10 to 20%. Currently estimation for river naturality widely used in rivers were consisted of a narrow wide a variety of items and did not reflect the actual.

• Journal of Korea Water Resources Association
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• v.47 no.12
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• pp.1165-1176
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• 2014

In a river bend the water surface is inclined by the centrifugal force toward the transverse section. If channel slope and flow rate increase, the gradient is rising generally. There are lots of the flood damage at the bends of mountain river because the flood water levels have exceeded frequently the levee levels which are added a free board to the design flood water level. Therefore the superelevation should be considered in designing the mountainous river bend. In present study it was proposed to estimate the superelevation at the bend of mountain river and the superelevation coefficient defined from multiplying the sub-factors. The values of the influence factors for the superelevation coefficient were suggested from analyzing the superelevation measured at the bends in Yangyangnamdae river and the hydraulic experiments in gravel-bed channel with a $90^{\circ}$ bend. The applicability of these methods to estimate the superelevation at the bends in mountain river was verified by the superelevation measured at the bend in Naerin river.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.44-53
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• 2005

The Nakdong River, which lies in a monsoon climate zone with warm rainy summers and cold dry winters, is a typical ecosystem showing the attributes of a regulated river. In 2003, the total annual rainfall (1,805 mm) was higher than the average of the past nine years from 1994 to 2002 (1,250 mm). In September a powerful typhoon, Maemi, caused a big impact on the limnology of the river for over two months. Among the limnological variables, turbidity in 2003 (37.4 ${\pm}$ 94.1 NTU, n = 54) was higher than the annual average for ten years (18.5 ${\pm}$ 2.3 NTU, n = 486) in the lower part of the river (Mulgum: RK 28). Furthermore, physical disturbance (e.g. stream bank erosion within channel) in the upstream of the Imha Dam (RK ca. 350; river distance in kilometer from the estuary barrage) in the upper part of the river was a source of high turbidity, and impacted on the limnological dynamics along a 350 km section of the middle to lower part of the river. After the typhoon, high turbidity persisted more than two months in the late autumn from September to November in 2003. Flow regulation and the extended duration of turbid water are superimposed on the template of existing main channel hydroecology, which may cause spatial changes in the population dynamics of plankton in the river.

• Journal of Wetlands Research
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• v.4 no.1
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• pp.43-50
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• 2002

The channel improvement plan has contributed to the flood damage reduction studies and the plan has mainly performed by the levee construction which creates the cut river. The cut river has mainly used as the agricultural and housing purposes. Recently, however, it is considered as a natural wetland for the purposes of a flood control and preservation of nature. So, this study compares the economical benefits according to the purposes of the cut river utilizations such as an agricultural, levee construction for flood damage reduction, and wetland. The study area is the downstream part of Kok-Neung stream which is a main tributary of Han river. The agricultural and levee construction benefits are estimated based on the 'Agricultural and Forestry Statistical Year' (2000) and the 'Standard for River Design' (2001). The benefit or value for the wetland utilization of the cut river is estimated by the enquete using questionnaire. As a results, for the case of which the cut river is used as an agricultural land, the present net benefit is estimated as 195.81 million won, for the levee construction, as 20853.00 million won and for the wetland, as 24692.89 million won. Therefore, the wetland is the best choice for the cut river utilization.

• Ecology and Resilient Infrastructure
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• v.1 no.2
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• pp.82-93
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• 2014

In recent years, "ecological river restoration" taking into account the flood control, water utilization and environmental aspects of rivers is actively being investigated. However, it is hard to understand the inhabitation conditions of living organisms that live on the river with distinct characteristics have been fully reflected, and with the use of limited methods, it ends in uniformed composition of artificial rivers and a mere customary stream channel maintenance, resulting in frequently disturbed stream channel habitats As a fundamental study for investigating the habitats of living organisms that live on rivers, this study intends to examine each habitat type by dividing domestic rivers into sand rivers and gravel rivers depending on the nature of rivers and dividing sections of each river into central river sections and natural river sections. As a result, more diverse habitat types of organisms were found in the gravel rivers rather than in the sand rivers, and the habitat types of organisms in the central river sections where the river restoration project have been already conducted reached approximately 56.3 % of those that appeared in the natural river sections.

• Journal of The Geomorphological Association of Korea
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• v.27 no.2
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• pp.29-46
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• 2020

In this study, changes in the fluvial landforms of the Yeoju section of the Han River, which was made up of the Han River Restoration Project, were examined through existing previous research data, government's environmental impact assessment data, satellite images, and field observations. For example, In the vicinity of Dori Island, the most upstream part of the study section, the location of the confluence of the Han River and Cheongmi Stream was changed, and it was found that a significant portion of the sand sedimentary layer disappeared. In the Bawuinupgubi area, the wetland, which is the first class in the ecological nature, was greatly modified, and the elevation of the ground rose as Gangcheon island and it was completely separated from the river by dredging The confluence of Geumdangcheon and the point bar of Yeonyang-ri in the south were also dredged, turned into an artificial waterfront park, and a chute channel remained in the form of a wetland was also developed as a recreational park. The deposional forms around Baekseok-ri islands also disappeared as dredging was carried out. Among the areas adjacent to the confluence of Bokcheon and Yangchon-ri Island, some sedimentay forms remains, but the abandonned channel between Yangchon-ri and the northern river bank has been changed into a riverside reservoir through dredging and embankment construction, and the waterway of the tributary river(Yazoo) has been greatly changed.

• Journal of Korea Water Resources Association
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• v.41 no.4
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• pp.395-404
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• 2008

It is important to understand the complex, various migration features of the alluvial channels for river engineering. In this study, the morphological changes and migration features of alluvial channels were investigated by analyzing the aerial photographs of active channels between 1972 and 2004 in Hapyeong Intake Station, Nakdong river. The lower channels were migrated from left bank to right bank and showed the features of braided channel in 2004. The instability of lower channels was increased due to the increased channel slope and width. The sinuosity of lower channels was decreased with time. As time increased, the increasing rate of lower channel and lateral migration rate were decreased. As a result of meso-scale regime analysis by using bankfull discharge, multiple row bars were developed, and suspended sediment load was governed in the flow as a sand bed channel.

• Journal of the Korean Geographical Society
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• v.48 no.5
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• pp.615-628
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• 2013

The waterfall can be formed by difference between the height of up and down part in new channel, is formed by channel avulsion that rapidly changing of river channel course. This study described types and processes of waterfalls by channel avulsion, and analyzed rates and factors of waterfall recession, on object to 7 waterfalls in South Korea. Bulyeong falls at Uljin-gun, Yongchu falls at Yeongdeok-gun, Jikyeon falls at Yanggu-gun and Gwangpum falls at Uljin-gun are formed by natural incised meander cutoff. Samhyeongje falls at Taebaek-si and Guryong falls are formed by river capture processes, and Palbong falls at Chungju-si is formed by artificial channel cutting for farm land secured. The locations of waterfalls gradually moved to upstream over time by head erosion. The recession rates were measured by 3~4m/ka on Bulyeong falls, Yongchu falls, Jikyeon falls and Samhyeongje falls, to estimate of formation age. Recession rates of these 4 waterfalls were analyzed that have clearly positive correlations with drainage area, precipitation, corrosion and weathering capability of bedrock, and initial height of waterfall.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.149-149
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• 2018

Prediction on initial motion of sediment is crucial to evaluate sediment transport and channel stability. The condition of incipient movement of sediment is characterized by bed shear stress, which is generated from force of moving water against the bed of the channel, and by critical shear stress, which depends on force resisting motion of sediment due to the submerged weight of the grains. When the bed shear stress exceeds the critical shear stress, sediment particles begin rolling and sliding at isolated and random locations. In Mountain River, debris flow frequently occurs due to heavy rainfall and can lead some natural stones from mountain slope into the bed river. This phenomenon could add additional forces to sediment transport system in the bed of river and also affect or change direction and magnitude of sediment movement. In this paper, evaluations on incipient motion of uniform coarse gravel under falling spheres impacts using small scale flume channel were conducted. The drag force of falling spheres due to water flow and length movement of falling spheres were investigated. The experiments were carried out in flume channel made by glass wall and steel floor with 12 m long, 0.6 m wide, and 0.6 m deep. The bed slopes were selected with the range from 0.7% to 1.5%. The thickness of granular layer was at least 3 times of diameter of granular particle to meet grain placement condition. The sphere diameters were chosen to be 4cm, 6 cm, 8 cm, 10 cm. The spheres were fallen in to the bed channel for critical condition and under critical condition of motion particle. Based on the experimental results, the Shields curve of particles Reynold number and dimensionless critical shear stress were plotted. The relationship between with drag force and the length movement of spheres were plotted. The pathways of the bed material Under the impact of spheres falling were analyzed.