• 대한지리학회지
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• 제33권spc호
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• pp.729-738
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• 1998

Under background of global change, regional and local environmental changes in short-term are significantly influenced by human activities in recent time. This paper deals with serious environmental problems which has become a barrier of sustainable development in the lower reach of Yellow River due to over use of diverted water from Yellow River and underground water from coastal plain. Some countermeasures for improving local environment and economic development are introduced in the paper.

• 한국물환경학회지
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• 제34권5호
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• pp.447-461
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• 2018

To realize river restoration that ecological characteristics of the river are reflected, we classified the river into four reaches of valley stream, upstream, midstream, and downstream based on substrate as well as riverbed gradient obtained from the relationship between distance from the river mouth, and above sea level. Considering that the rivers of Korea have been dominated by various and intense artificial interferences over a lengthy period, we determined cross sectional range of the river based on the geological map and clarified transformation degree by reach. Vegetation profile diagram was prepared by depicting horizontal range and vertical stratification of major vegetation appearing in a belt transect of 10 m breadth installed between weirs constructed in both sides of the river. Restoration models by river reach were prepared based on breadth of waterway, bare ground, herb, shrub, and tree dominated vegetation zones on vegetation profiles wherein a flooding regime was reflected. Species composition information collected from vegetation established in each zone was systematized to use for restoring each reach ecologically. Further, background that longitudinal reaches and horizontal zones were divided, was discussed by comparing with case studies in foreign countries. In addition, necessity of ecological restoration of the river was discussed based on degree of integrity of Korean rivers, ecological significance of riparian vegetation, and importance of reference information for ecological restoration of the river.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.173-173
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• 2015

The flood water level in tidal river is determined by the joint effects of flood discharge and tidal water levels at downstream boundary. Due to the variable tidal boundary conditions, the evaluated design water levels associated with a certain flood event can be significantly different. To avoid determining of design water levels just by a certain tidal boundary condition and remove the influence of variability in boundary condition from the evaluation of design water levels, a probabilistic approach is considered in this study. This study focuses on the development of a method to evaluate the realistic design water levels in tidal river with taking into account the combined effects of river discharge and tidal level. The flood water levels are described by the joint probability of two driving forces, river discharge and tidal water levels. The developed method is applied to determine design water levels for the tidal reach of the Han River. An unsteady flow model is used to simulate the flow in the reach. To determine design water levels associated with a certain flood event, first, possible boundary conditions are obtained by sampling starting times of tidal level time series; then for each tidal boundary condition, corresponding peak water levels along the channel are computed; and finally, design water levels are determined by computing the expectations of the peak water levels. Two types of tides which are composed by different constituents are assumed (one is composed by $M_2$, and the other one is composed by $M_2$ and $M_2$) at downstream boundary, and two flood events with different maximum flood discharges are considered in this study. It is found that (a) the computed design water levels with two assumed tides have no significant difference for a certain flood event, though variability of peak water levels due to the tidal effect is considerably different; (b) tidal effect can reach to the Jamsil submerged weir and the effect is obvious in the downstream reach of the Singok submerged weir; (c) in the tidally affected reach, the variability of peak water levels due to the tidal effect is greater if the maximum flood discharge is smaller.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2004년도 학술발표회
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• pp.1335-1339
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• 2004

A hydro-geomorphologic change in a sand bed channel reach and vegetation expansion by changes in the How regime is analyzed in this study. Field and aerial photo surveys, basic hydrological analysis about flow regime change due to two dams, Andong Dam and Imha Dam, on the upstream river and computer modeling are conducted. Two Dams in the study reach have obviously affected downstream channel in many ways including the bed particle coarsening, vegetation expansion on the sandbars and following river channel braiding. The phenomenon of no vegetation on the large point bar in front of Hahwe Village seems due to disturbance of the sandbar surface probably due to the cross flow in the meander reach during the flood. Another reason for no vegetation is that the sandbar on this reach has lower subsurface water lovels, as compared with the others in the up- and downstream of the reach where vegetation expanded, which would hinder vegetation from germinating and growing on the sandbar.

• 대한토목학회논문집
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• 제13권5호
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• pp.157-163
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• 1993

미공병단에서 개발된 하상변동계산모형인 HEC-6를 대청댐 하류의 금강에 적용하여 대청댐 축조에 따른 하류 하상의 변화를 살펴보았다. 대청댐은 금강의 중류에 위치하고 있으며, 댐 하류는 하상이 대부분 세사(細砂)와 중사(中砂)로 이루어져 있는 전형적인 충적하천으로 댐축조에 따른 하상변동이 예상되는 구간이다. 분석결과 댐 직하류 15km 구간은 대청댐 축조에 의해 하상이 2~3m 정도 현저하게 저하되었으며, 이 구간의 현재의 하상은 자갈과 호박돌 등에 의한 장갑화 현상에 의해 더 이상의 심각한 하상저하는 없을 것으로 예상된다. 또한, 연구대상구간내에는 대규모 골재채취로 인하여 국부적으로는 2m 이상이나 하상이 저하된 곳도 있다. 반대로, 대상구간의 하류부인 규암 수위표 상류 20km 인근의 하상은 0.5~1m 정도 상승하였다. 이 구간의 하상변동을 모의하기 위해 HEC-6 모형을 적용한 결과, 이 모형이 장기간의 하상변동을 비교적 적합하게 모의할 수 있음을 알 수 있었다. 또한, 추후 40년간의 하상변화를 모의한 결과, 이 구간은 장래에는 하상변동이 별로 없는 안정된 상태를 보이고 있다. 다만 중상류 일부 구간은 1~2m 내외의 하상저하, 하류구간은 0.5m 정도의 국지적 하상상승이 발생할 것으로 예상된다.

• 한국수자원학회논문집
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• 제35권6호
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• pp.715-727
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• 2002

하도구간의 도달시간은 일정 구간별로 하도길이를 홍수가 하류로 유하하는 평균유속으로 나눔으로써 산정 할 수 있으며, 유역추적법에 의한 홍수량 산정 시 필요한 저류상수 등과 매우 밀접한 관계를 가지고 있다. 이러한 도달시간을 산정 할 수 있는 경험공식이 많이 제시되고 있으나 경험공식별로 계산된 도달시간은 일반적으로 큰 편차를 나타내고 있다. 본 연구에서는 100개 이상 하천의 확률홍수량에 대한 수면곡선계산 자료에서 구간별 하도의 평균경사와 평균유속을 수집하였다. 이러한 평균경사와 평균유속과의 관계를 회귀분석한 결과를 살펴보면 동일한 평균경사에서도 평균유속이 많이 산포 되어 있음을 알 수 있으며 이는 지역별 확률강우량의 차이와 하천별 유역면적의 차이 등에 기인한다. 따라서, 지역별 확률강우량의 차이와 하천별 유역면적의 차이에 대한 영향을 제거하는 방법을 개발하여 일반화된 평균경사-평균유속 관계를 제시하였다. 이에 따라 하천종단에서 구간별 평균경사를 산정하면 일반화된 평균경시-평균유속의 관계를 사용하여 일반화된 평균유속을 산정 할 수 있으며, 이를 지역별 확률강우량의 차이와 하천별 유역면적의 차이에 대하여 보정하여 대상하천에 대한 평균유속을 산정하고 이를 이용하여 도달시간을 산정 하게된다.

• 한국콘텐츠학회논문지
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• 제11권6호
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• pp.486-494
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• 2011

유역이나 하천의 변화에 따른 하상의 상승이나 하강은 하천 관리에 있어 핵심적인 요소이다. 하천의 하상 변동을 분석할 때, 기준이 되는 것은 최심 하상고나 평균하상고의 변화이다. 이 때 평균하상고는 계획 홍수위에 대한 하상의 평균이다. 본 연구는 하상 변동 분석에서 기존의 최심 하상고나 평균하상고를 이용할 때 발생하는 제반 문제를 지적하고, 연평균 홍수위에 대해 하상을 평균하는 새로운 평균하상고 개념을 제시하였다. 제안된 방법을 검토하기 위해 낙동강의 1983년, 1993년, 2005년의 3개년의 하상 자료를 이용하여 하상 변동 경향성을 분석하였다. 그 결과 낙동강에서는 1983~1993년 사이에는 대규모 하상 저하는 없었으나, 1993~2005년 사이에는 상당한 규모의 하상 저하가 발생하였다. 1993~2005년 사이에 중류부인 120~200 km 구간에서는 평균적으로 2~3 m, 최대 5 m 정도의 하상 저하가 발생하였고, 그 상류부인 200~240 km 구간에서는 1~2 m 정도의 비교적 작은 규모의 하상 저하가 발생하였다. 그러나 내성천 합류점보다 상류 구간 (240 km 이상의 구간)에서는 하상 상승과 하강은 거의 대부분 국부적인 현상에 머물고 있으며, 대규모 하상 변동이 없다. 이러한 낙동강 하상 저하의 주 원인은 대규모 골재 채취임을 밝혀내었다.

• 한국환경과학회지
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• 제20권10호
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• pp.1309-1317
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• 2011

This study selected 6 river reach, which have various curved-channel, included in an object of study as making the Nakdong River, which is a real nature river, as a point of an object of study by using SMS RMA-2 model, a 2D numerical analysis model, and applied project flood and analyzed and examined characteristic of hydrological property and super-elevation, which includes characteristic of the velocity of a moving fluid. As a result, in a river reach, whose width is wide, angle of curved-channel has impact on the velocity of a moving fluid of inside of curved-channel and in a river reach, whose width is narrow, the radius of curvature and width of the river have impact on the velocity of a moving fluid of inside of curved-channel. Also it found out that the ratio of reduction in water-level of inside of curved-channel is more bigger than ratio of increasing in water-level of outside of curved-channel when project flood is increasing and angle of curve is increasing. Based on this, this study would be used as a expectation of danger and preliminary data in planning real river or a business, that creates an environment.

• 한국환경복원기술학회지
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• 제11권3호
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• pp.74-86
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• 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.

• 한국환경복원기술학회지
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• 제12권3호
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• pp.83-97
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• 2009

The objects of study is to propose criteria for physical river disturbance assessment and as case study to show the application results for river improvement. For this purpose, the river disturbance assessment method for past disturbance process and the present-day potential natural state of stream is proposed. To assess the disturbance of the Youngcheon River caused by river improvement, One ares of Nam River was selected for the reference reach and two areas of Youngcheon River were selected for the comparison reach. And these reaches were surveyed and analyzed according to applying criteria of the river disturbances assessment. The assessment indices were physical factors as like epifaunal (bottom), embededness, velocity/depth regime, sediment deposition, channel flow status, channel alteration, frequency of riffles, bank stability, vegetative protection and riparian zone etc. The results showed that physical river environment in Youngcheon River area was disturbed by artificial revetment and bed excavation, consequently this disturbance give rise to impact of ecosystem in river. Hereafter, the criteria for river disturbance assessment are needed to consider various river characters as bed materials and bed slop etc.