• Journal of the Korean Geographical Society
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• v.46 no.3
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• pp.304-318
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• 2011

The types, distributional and shape properties of abandoned channels in Korea are classified and examined. There are 409 abandoned channels in Korea and they can be classified into the 6 types such as the incised meander cutoff, stream piracy, distributary, artificial incised meander neck-cutoff, channel straightening of free meander and distributary streams. The abandoned channels by incised meander neck-cutoff showing the most frequency with 266, have the topographical properties of high altitude and steep relief and frequently distribute in Gangwon and Gyeonbuk Province and in the upper reaches of main stream of Nakdong-River, and Dal-River and Pyeongchang-River, tributaries of Namhan-River. The most frequency areas of abandoned channels by distributary, channel straightening of free meander and distributary streams are the lower reaches of Namhan-River and main stream in the lower reaches of Nakdong-River, Mangyeong-River and Yeongsan-River, and Geumho-River, respectively. The abandoned channles by incised meandering neck-cutoff and stream piracy are relatively used as farmlands or forests due to the high altitude and relative altitude from the river bed.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.547-559
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• 2012

Abandoned channel is vestiges of running in the past. Abandoned channels have been formed mostly by artificial river maintenance through channel straightening in Korea. Managed properly, these now abandoned channels can provide habitat for wildlife, maintain biodiversity of aquatic life, security against flooding and recreation area for human. However, because the areas are officially classified as abandoned, the channels is collapsing and decaying from years of neglect. This study suggested functional assessment for wetland-type abandoned channel in order to provide appropriate management and investment. For this reason, The study will examine and evaluate these channels with regard to the following four major criteria (Natureless, Habitat, Water-friendliness and Water quality) and 21 indices. Consequently, abandoned channel in two Nakdong river sites, site 1 was needed for protection or improvement in the medium to longer term, while site 2 was in good condition. This evaluation method will be helpful to manage wetland-type abandoned channel in Korea and will be able to use National River Health Program.

• Journal of the Korean Institute of Navigation
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• v.25 no.1
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• pp.1-9
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• 2001

It is well known that, especially in the case of full-bodied ship, the course stability may become the severest among 4 items of requirement in Interim Standards for Ship Manoeuvrability adopted by IMO in 1993. The purpose of this study is to find some ideas for characteristics of fluid flow pattern around ship's stern in manoeuvring motion with parameter of changes in rudder size. We carried out two kinds of model experiment in obliquely running condition at circulating water channel. One is measurement on straightening effect of incoming flow to rudder and the other is experiment on flow visualization around the gap between rudder and stern-bottom. We discuss the correlation between the flow characteristics around ship's stem and flow straightening effect at rudder from the viewpoint of course stability. As a result, it is clarified that the gap between rudder and stern-bottom plays an important role in course stability of full-bodied ship. It is pointed out that there is quite a possibility of bad course stability as the gap between rudder and stern-bottom decreases.

• Journal of Korea Water Resources Association
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• v.42 no.5
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• pp.397-406
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• 2009

River is able to change by various environmental factors. In order to conduct restoration design of abandoned river channels, it is necessary to evaluate the river through the analysis of past and present river channels. River evaluation requires various data, such as geometry, hydraulic and hydrology, but there is a lot of difficulty to understand topographical information of river change on time and space due to a lack of past data by domestic conditions. This study analyzes the changes in past and present river channels and examines the applicability of river channel evaluation through image analysis using aerial photographs and 1918 year's map. Aerial photograph analysis was conducted by applying the image analysis method and GIS analysis method on Cheongmicheon. As a result of this analysis, we have quantitatively identified the form and size of abandoned channels, changes in the vertical-section and cross-section length of rivers, and micro-landform changes. More importantly, we verified that morphological changes in sandbars due to artificial straightening are important data in identifying the state of current river channels. In these results, although image analysis technique has limitations in two-dimensional information from aerial photographs, we were able to evaluate the changes in river channel morphology after artificial maintenance of the river.

• Journal of Ocean Engineering and Technology
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• v.35 no.6
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• pp.446-456
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• 2021

To build an environment facility of a large-scale ocean basin, various detailed reviews are required, but it is difficult to find data that introduces the related research or construction processes on the environment facility. The current generator facility for offshore structure safety evaluation tests should be implemented by rotating the water of the basin. However, when the water in the large basin rotates, relatively large flow irregularities may occur and the uniformity may not be adequate. In this paper, design and review were conducted to satisfy the performance goals of the DOEB through computational numerical analysis on the shape of the waterway and the flow straightening devices to form the current in the large tank. Based on this, the head loss, which decreases the flow rate when the large tank water rotates through the water channel, was estimated and used as the pump capacity (impeller) design data. The impeller of the DOEB current generator was designed through computational numerical analysis (CFD) based on the lift surface theory from the axial-type impeller shape for satisfying the head loss of the waterway and maximum current velocity. In order to confirm the performance of the designed impeller system, the flow rate and flow velocity performance were checked through factory test operation. And, after installing DOEB, the current flow rate and velocity performance were reviewed compare with the original design target values. Finally, by measuring the current velocity of the test area in DOEB formed through the current generator, the spatial current distribution characteristics in the test area were analyzed. Through the analysis of the current distribution characteristics of the DOEB test area, it was confirmed that the realization of the maximum current velocity and the average flow velocity distribution, the main performance goals in the waterway design process, were satisfied.

• Journal of the Korean association of regional geographers
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• v.14 no.1
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• pp.1-18
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• 2008

If there is no choice but to be urbanized, we should examine how human interference has had influences on the area to keep the river environment safe and stable. This study is aimed at finding improvement by examining the effect of human interference in Gapcheon river in Daejeon, which is developing fast. Distinctive features of human interference in Gapcheon river are followings. First, middle and upper reaches of Gapcheon river are being maintained and restored focusing on flood control but are scheduled to develop city and channel. Second, the rear area of middle and lower reaches of Gapcheon river is already developed into an urban district and solidified into artificial stream for leisure activities installing the artificial structure for fun. Third, lower reaches of Gapcheon river are in an unstable condition because of straightening waterway and developing rear area of river. Up to now, geographical features and bio-diversity of Gapcheon river has been ruined by the artificial management of river centered for technical engineering. From now on, followings should be considered for management of urban river. First, it is focused on maintaining eco system by itself than usage for human. Second, natural features of rear area of river should be taken into consideration and should be preserved before developing urban city and hills, back marsh, channel deposit and swamp to directly have an influence on river.