• Journal of The Geomorphological Association of Korea
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• v.18 no.2
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• pp.53-63
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• 2011

The changes and causes of channel section in Naeseongcheon River, a tributary of Nakdong River, during the long(1984~2001) and short(2009~2011) periods are analyzed. There are the declines of channel height with a maximum of approximately 2m in the most areas of the lower reaches during the past 20 years. These are thought as the influences of active aggregate collections and river dredging. The size of sand bar within the channel at the NM1 decreases greatly during the past 2 years. This may results from the decrease of sediment supply due to the Yeongju Dam construction in the upper reaches. However, the NM2 and NL2 where the natural channel are preserved experience the slight increase of height during the past 2 years. Therefore, the anthropogenic channel interferences in Naeseongcheon River have greatly influenced on the declines of channel height by the decrease of sediment supply.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.452-455
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• 2009

The Nakdong Delta can be identified by two different geomorphic units. The first one is the upper delta. This is mostly composed of inter-distributary islands that are largely influenced by fluvial processes and attributed to the development of these islands along the river. The other one is the lower delta which is mostly composed of beach ridges. Barrier islands are largely effected by wave processes promoted by the development almost at a right angle to the river. Influenced by the longshore current which flows to the same direction, barrier islands located in the Nakdong river estuary are developing from east to west direction. As a result, the eastern end of the barrier islands are growing toward the north-west direction effected by tidal current which moves toward the same direction. Barrier islands include the Sinho Island, the Jinwoo Island, the Daema deung, the Janga Island, the Baghap deung, the Sae deung, and the Chulsae deung(Doyeo deung). They have orderly emerged from the sea since 1861. Since 2008, a new Deung, a sand dune growing under sea, has been developing rapidly from Chulsae deung to the Dadaepo beach. It made the sailing of small fisher boats impossible. Tidal currents transported a lot of sand and silt around the barrier islands. The landscape of Nakdong river estuary where many barrier islands are distributed will change rapidly affecting land environment.

• Korean Journal of Ichthyology
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• v.27 no.4
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• pp.300-305
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• 2015

The characteristics of 11 spawning sites in the natural environment of the Korean endemic species, Liobagrus somjinensis were investigated in the Yocheon (stream) of Seomjingang (river), located in Sikjeong-dong, Namwon-si, Jeollabuk-do, Korea from May to June 2015. The spawning sites had largely two parts, the upper region close to the surface of the waters and under region at bottom: the upper part was covered with a large and flat boulder over about 256 mm in size, whereas the under part consisted mainly of pebbles and sand. The large boulder put on the upper region may be seen as a bulwark for guarding eggs laid at the under (bottom) region. All the sites under the boulder showed a similar structure having a small hollow filled with an egg mass and an individual (male). The spawning bottoms left clean having no any benthic invertebrates and detritus. The egg shape was spherical, yellow and covered with a transparent membrane and the egg size was $3.31{\pm}0.15mm$ (n=30) in diameter. The development stage of each egg mass under the boulder was almost same from morula stage to formation stage of eye lens. The average number of eggs in 11 spawning sites was $121{\pm}35.5$ (84~176) and the average number of female fecundity in ovary was $143{\pm}31.3$ (110~232).

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.4
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• pp.62-73
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• 2003

The study was to apply a mat style reed planting method at confluence to improve plants growth conditions by relaxing disturbed topographical base due to water flow and was intended to review the effect to build up a vegetation strip by monitoring process after the construction. First off, We've attempted to construct reed mats on selected sites as confluences of Tan and Gaehwa stream and then examined and analyzed characteristics of soil and vegetation community. As the results of the examination, the soil texture was proven to be a mix of sand and loamy sand and be 6.3 ~ 7.0 soil pH. In addition, it contained 1.0 ~ 4.6% of organic matter, 0.04 ~ 0.22% of T-N and 27.8 ~ 41.2% of water content. For its vegetation structure, the Tan stream confluence was first actually a point bar without plants prior to the construction but 8 kinds of hygrophytes including Persicaria hydropiper and 9 kinds of terrestrial plants such as Potentilla supina, Artemisia annua, and Alopecurus aequalis var. amurensis. On the other hand, the Gaehwa stream confluence contained 6 kinds of hygrophytes such as Bidens frondosa and other 11 kinds of terrestrial plants prior to the construction while it produced 7 kinds of hygrophytes including Ranunculus ternatus as well as Phragmites australis and 9 kinds of terrestrial plants such as Potentilla supina after the construction. For the Phragmites australis, almost of them was weathered away in early days just after planting because of development period passed, but on May, six months later from planting, it was investigated that its length was approximated as 65 ~ 85cm with 75% coverage and that the number of it was 437 ~ 633/$m^2$. The study was shown that reed mats can improve environmental conditions of disturbed topographical base, enabling natural growth of various riparian vegetation including the introduced plant, reed. In the meantime, it was supposedly judged that to recover or build up a vegetarian strip, supplementary materials should be prepared to help produce and grow plants because it is not probable to expect river drift by water flow at confluence and that corrosion, burying or inundation owing to changes of water lever should be considered.

• Journal of the Korean Geotechnical Society
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• v.31 no.10
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• pp.17-28
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• 2015

The strict regulations on eco-friendly construction and the significant reduction of natural aggregate resources have raised public concerns on the utilization of recycled aggregates for backfilling a power transmission pipeline trench. In this paper, the particle breakage of concrete-based recycled aggregates and river sand has been experimentally studied during the standard compaction test. The applied compaction energy does not significantly break the river sand particles down, and thus causes no change in the compaction curve, thermal resistivity, and particle gradation characteristics. On the other hand, considerable particle breakage was observed in case of the three recycled aggregates. Such particle breakage leads to enhancing compaction effort, reducing thermal resistivity, and changing particle gradation curve with finer particles that are broken during the first compaction. In addition, particle breakage is more dramatic in lower water contents because pore water may damp down the compaction energy.

• The Korean Journal of Ecology
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• v.18 no.1
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• pp.55-62
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• 1995

This study was conducted to investigate the distribution pattern of plants on streamside of Kyonganchon, which is a tributary of the Han River, and to determine the relationships between plant distribution and environmental factors. Fifteen study sites were selected along the Kyonganchon, and vegetation distribution pattern and soil environmental factors were determined. The most frequently ocurring species in the study sites were Persicaria thunbergii, Persicaria hydropiper, Echinochloa crus-galli and Bidens frondosa, and among them the two Persicaria species were dominants of the community. Many species showed different distribution along the stream:Chenopodium album, Equisetum arvense and Setaria viridies occurred in the upstream region, while Rumex crispus, Leonurus sibiricus and Rorippa islandica occurred in the middle and downstream regions. Analysis of soil properties showed that organic matter and clay content were higher in the upstream region while sand content was higher in the downstream region. The results of DCA ordination showed that axis one was positively correlated with organic matter and clay content and negatively correlated with sand content, indicating that the distribution pattern of vegetation along the Kyonganchon was determined by elevational gradient from upstream to downstream region or gradient of stream width and water level, and by soil organic matter content and soil texture related to these gradients.

• Journal of The Geomorphological Association of Korea
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• v.24 no.4
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• pp.91-101
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• 2017

The Okjukdong dune in Daecheong Island attracts national attention because of its unique landscape that is not covered by vegetation. However, there has been little knowledge on the timing of the dune formation, associated wind regime, and conservational strategies. In this study, we used OSL dating and grain size analyses to reveal the history of the dune development. In addition, we analyzed the wind regime in the dunefield which is surrounded by artificial coastal forest. The fine sand at Okjukdong underlain by a colluvial gravel layer indicates that the dune has been developed since at least 5 ka. Aeolian sands were found to be deposited around 700 years ago. The dunefield appears to have been severely eroded 30~60 years ago. The dune landscape has been destroyed after constructing a windbreak forest around the dunefield. The sand seems to be moving south and north with the season.

• Korean Journal of Ichthyology
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• v.21 no.4
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• pp.253-261
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• 2009

Habitat environment and feeding habitat of Iksookimia koreensis and Cobitis lutheri were investigated in the Mangyeong River, Jeollabuk-do, Korea from 2005 to 2006. They together inhabit the upper and middle stream, but they showed differences in their microhabitat. I. koreensis inhabited the stony zones of relatively rapid waters with a water depth of 30~60 cm, whereas C. lutheri lived in the sandy zones of relatively slow waters with a depth of 30~100 cm. The two species were active during daylight hours from March to October but hibernated in the winter season. During hibernation I. koreensis still lived in the gravel and stone and C. lutheri burrowed in the sand. I. koreensis ingested mainly chironomid and other aquatic insects, whereas C. lutheri fed mainly on Chironomidae, Copepoda and Branchiopoda. The feeding rate of both species was highest in April and September, but they did not feed in the winter.

• Journal of The Geomorphological Association of Korea
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• v.17 no.4
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• pp.29-40
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• 2010

The Palgye Plain, located in Chilgok, Buk-gu, Daegu-si, is a floodplain by Palgye-River rising from Mt. Ga one of the mountains in Ring Typed Mountains of Mt. Palgong. The geomorphic surfaces in the study area can be divided into the natural levee, back marsh and confluent fan, and the natural levee and fan have been used as important regions of human activities since the Bronze Age. The alluvium sediments of Palgye-River can be subdivided into the bedrocks, lower gravel deposits, lower sandy deposits, lower silty deposits, upper sand and gravel deposits, and upper silty deposits from the bottom according to the formative ages. The lower gravel deposits correlated to the last glacial stage and the rest to Holocene, respectively. Confluent fans were also formed during the last glacial stage. Moreover, The landscape with land use after 20C was changed to apartment area due to civilization differently from which reflected the characteristics of geomorphic surfaces in the past.

• Journal of Korea Water Resources Association
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• v.42 no.2
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• pp.141-148
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• 2009

Each river in each country has peculiar channel characteristics at every section. Korea consists of mountains at the rate of 70%. Due to this, the sections that display unique channel form are scattered. One of the typical features is the narrow pass of channel section that presents in the process of the generation of alluvial channel and deformation channel. Around as this narrow pass of channel, it often comes to be regular flood disaster section. Regardless of this situation, investigations and plans that reflect channel characteristics at the narrow pass of channel have been wholly wanting until now. In accordance with this, we have investigated and analysed hydraulic significance and channel form of the narrow pass of channel in Seonsan in this study. The study has found real minute classification of sediment phenomenon at river bed of low flow channel on investigation section which is sand-bed river, but it was vaguely difficult to conclude that classification of sediment arises from explicit natural force. We were able to assume that the phenomenon comes from gentle bed slope, supply of river bed materials which is nearly uniformity. However, classification of sediment would come from collecting an aggregate rather than natural force. And we found that compound cross section conversion has been developing dramatically with channel form of movable bed section referring to movement which was active before at drainage district of the narrow pass of channel. With this, we could find the phenomenon that river width of low flow channel diminished largely. This kind of situation implies that it may cause compound section weighting, flood dimension decreasing, revetment at low flow channel or the local scour at bottom of levee when extraordinary flood occurs.