• Journal of Environmental Science International
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• v.22 no.3
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• pp.291-301
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• 2013

Sediment from the upstream channel has been deposited near the Nakdong River Estuary Barrage (NREB) due to the mild slope and decreased velocity. The annual mechanical dredging to ensure the flood capacity has been performed to remove the deposited sediment. However, the dredging method is not considered as an effective countermeasure due to high cost and long time to operate. Therefore, many methods for sedimentation reduction have been proposed for NREB. Especially, the channel contraction method to mitigate sedimentation problem by changing the channel geometry from 2 km to 3 km upstream of NREB has been recently suggested as an effective countermeasure. However, there is the possibility that the channel contraction method induces flood level increase compared to original condition. Therefore, it is necessary to investigate quantitatively the flood level changes in the upstream and downstream section due to the channel contraction method for NREB. In this study, water level changes by 10% channel contraction of whole width has been evaluated using the HEC-RAS model and simulated with and without channel contraction for various flood discharge. As a result, water level in the section where the channel was contracted was decreased by 0.02 m and flood level at the upstream of channel contracted was increased up to 0.015 m for the 500-year flood.

• Korean Journal of Construction Engineering and Management
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• v.13 no.2
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• pp.137-146
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• 2012

Recently, due to construction of the recession quantity of unsold houses is increasing and construction company is experiencing financial difficulties. As a result, construction is being ousted, or workout. Accordingly, construction may be devising a method for oneself like salary cuts, layoffs as part of the rationalization of management. But in this way may be increasing employees's perception about job insecurity and payment unsatisfaction. This has the potential to do employees turnover. Turnover has be known that it brings both positive and negative results to the organization. But if new employees leaves early, the positive aspect of the organization will be less likely. In order to solve these problems, new employees turnover intention will be necessary for the thorough management. The purpose of this study is to identity how the perception of job insecurity, payment satisfaction, organizational commitment, excessive workload, competitiveness for employment and job suitability affect new employees turnover intention. As the degrees of impacts of variables affecting turnover intention of new employees might be different between small to medium and large construction companies, this research also compares the differences between these two groups and suggest measures for reducing turnover intention.

• Journal of Korean Society of Forest Science
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• v.101 no.4
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• pp.656-662
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• 2012

This study has been undertaken to research the characteristics of growth of Pinus thunbergii Parl., which were planted in Uljin-gun, Gyeongbuk, Coast Disaster Prevention Forest. The total amount of 3600 trees of 9 sand dune stabilizing hedges were monitored in the past 4 years. The relationship between tree growth with environmental factors such as wind speed, soil conditions and sand-accumulation fences has been compared and investigated. To increase the growth increment of coastal disaster prevention forests, the development of sand-accumulating fences is the most important factor in controlling wind speed effectively. The monitoring for the maximizing wind-break effect of the sand-accumulating fences should be investigated when building coastal disaster prevention forests.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.342-342
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• 2011

댐의 건설로 인해 자연적인 물의 흐름이 댐 운영에 의하여 조절되기 때문에 유사의 연속성 및 유량의 변화에 따른 지형 환경적 변화가 예상된다. 따라서 영향분석을 위한 체계적인 조사 및 연구가 필요할 것이다. 본 연구는 내성천 영주댐 건설 예정지로부터 48.4km 하류인 회룡포 구간에서 하상변동이 예상됨에 따라 현장 조사를 수행하고, 장래변화를 예측하기 위하여 수치모델을 수행하였다. 수리학적 변화량은 금회 수립중인 하천정비계획의 계획 홍수량인 댐건설 전 4,040cms, 댐건설 후 2,934cms로 구분하고, 유사변화량은 영주댐 실시설계 보고서결과를 적용하여 분석하였다. 한편 2001년과 2010년의 실측종단변화를 검토한 결과, 회룡포 구간에서 0.5m~1.7m의 퇴적이 진행되고 있음을 알 수 있었다. 수치모델 및 실측한 데이터를 종합적으로 판단한 결과, 단기호우사상에 대해 댐 건설 후 회룡포 구간의 사주퇴적능력은 -0.05m로 감소되어 그 영향은 비교적 미미할 것으로 분석 되었고, 대부분의 변화는 주수로에서 -0.5~0.5m로 변화될 것으로 예측되었다. 하상 변동의 양상은 실측한 10년간의 종단변화와 같은 경향성을 보이며, 횡단번호 No.15 이후로 0.5m이상 퇴적이 이루어 질 것으로 예측되었다. 본 연구결과는 댐건설로 인한 하천 하상변화에 대한 특성을 파악하고 하천공사 나 수리구조물 설계의 기초자료로 활용될 수 있을 것으로 판단되며, 향후 지속적인 모니터링 및 조사를 통하여 하상변동양상을 관측하고 분석할 필요가 있을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2013-2018
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• 2007

최근에 발생하는 홍수특성은 단기간의 국지성 집중호우로 본류 대하천보다는 상류지역 지류하천이 특히 취약하여 이에 대해 하류보다는 상류, 본류보다는 지류위주로 과거와 다른 치수정책 전환이 요구되고 있다. 정부에서도 과거 치수대책이 제방위주의 선적인 개념에서 면적인 개념의 유역치수 중심의 방어형태로 추진하고 있으나, 상류지류 하천에 대한 홍수방어 계획은 부족한 실정이다. 지류하천에 홍수가 발생하면 홍수도달시간이 짧아 첨단홍수예보시스템으로도 대처가 곤란한 문제가 있으며, 이외에도 홍수와 함께 산사태가 빈번히 발생되고 토석류, 유목류가 한꺼번에 동반 유입되어 인명과 재산피해가 크게 발생하는 특징을 가지고 있다. 작년 7월 강원지역 집중호우에서도 인제군, 평창군 등 지류에 인명과 재산피해가 크게 발생한 것도 이와는 무관하지 않을 것이다. 최근 국지성 집중호우가 빈번히 발생하는 것은 기상적 측면이 아니더라도 우리나라는 하천경사가 급하고 산지가 국토의 약 70%로 구성되어 있어 지형적 측면에서 평화의댐(지체댐), 군남홍수조절지, 한탄강 홍수조절댐 등 대규모 홍수방어댐 도입시 홍수조절 효과가 우수하나, 대규모 댐건설에 따른 지역민의 불신, 환경단체 반발, 사회적 미합의 등 현실적인 제약조건이 많으므로 현실적이고 상류지역 지류하천에 효과적인 홍수조절을 위해서는 보호하고자 하는 도시 및 주요시설물시설에 대하여 소규모 홍수저류지(Detention Dam)를 상류 지류하천에 단일 또는 군(群)으로 도입하여 설치하는 방안을 적극적으로 추진하여야 한다고 사료된다. 소규모의 홍수저류지는 평상시에는 자연상태와 같이 전량 방류하고 갑작스런 홍수발생시 첨두홍수량을 지체하거나 감소시켜 하류지역에 홍수피해를 줄이는 시설로 기존의 댐보다는 규모가 적고 평상시에는 자연하천과 같이 물을 담지 않아 환경변화에 의한 영향이 적어 사회적 합의가 유리하고 친환경적이며, 홍수기에는 비어 있는 저류용량을 전량 활용이 가능하여 저수규모에 비해 홍수조절효과는 큰 장점이 있다. 특히 홍수조절의 본래 목적 외에도 초목류, 토석류 및 각종 부유쓰레기를 차단하는 사방댐 역할과 하류하천의 퇴사량 감소 등 다방면으로 효과가 있어 독일, 일본 등 선진국에서는 적극적으로 추진되고 있다. 본 연구에서는 선진 외국에 도입된 홍수저류지 사례를 조사 및 검토하여 국내에 적용 가능한 유역분담형 홍수저류지 규모 및 방식, 홍수저류지 도입방안과 향후 연구방향 제시하였다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.45-61
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• 1988

The purpose of this study is to develop regression equations between annual specific sedi- ment of reservoirs and physiographic factors of watersheds. 122 irrigation reservoirs, which have irrigation areas equal to or larger than 200 ha, located in Korea except Cheju province are used in the analysis. Simple regression analyses between the specific annual sediment and each of the physical characteristic factors of the reservoirs are carried out at first. Then, multiple regression analyses between the annual specific sediment and the physical characteristic factors with high correlation coefficients in the simple regression analyses are made. The results obtained from this study are as follows : 1. The results of the sirnple regression analyses show that in each province the watershed area, the length of mainstream, the circumferential length of watershed have high cor- relation coefficients (R=0.814-0.986), and that drainage density, reservoir capacity per watershed area, drainage frequency, basin relief have low correlation coefficients (R=0. 387-0.955). 2. The purposed multiple regression equations between the annual specific sediment of reservoirs and three major characteritic factors of watersheds, namely, the watershed area, the circumferential length of watershed, and the length of mainstream, are proposed as given in Table 2. 3. The result of the simple regression analyses with respect to the reservoir elevation except Jeonnam province, which has very different characteristics comparing to other provinces, shows that watershed area, main stream length and circumferential length have high correlation coefficients (R=0.806-0.884) in low-elevation reservoirs and intermediate- elevation reservoirs, but low correlation coefficients (R=0.639-0.739) in high-elevation reservoirs. 4. With respect to the reservoir elevation, the proposed multiple regression equations bet- ween the annual specific sediment of reservoirs and the three major characteristic factors of watershed which have high correlation coefficients are proposed as given in Table 5.

• Journal of Korea Water Resources Association
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• v.30 no.2
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• pp.107-118
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• 1997

The Upper Fenhe Reservoir System studied by KOWACO to supply water to Taiyuan City, capital of Shanxi Province in China, is a very complicated one. Many reservoirs will be connected serially and it will be operated as a multi-purpose and multi-criteria system because several objectives and appraisal functions are taken into account regarding system operation. For reservoirs in the system, the critical system operation objectives are to minimize water shortage and reservoir sediment. Furthermore the reservoir system will be jointed with a large-scale pumping system, namely Yellow River Diversion Project. The water development cost in the Yellow River Diversion Project is much higher than that of reservoir system, and around the year 2020 the diversion volume will be twice of the surface water available in the Upper Fenhe Basin. In this study, an optimization technique for connecting the system of reservoirs and pumping station was developed to solve a conjunctive low River Diversion Project. The developed scheme includes a suggestion on the combining methodology of real reservoir system and pumping system using imaginary reservoir concept for the Yellow River Diversion Project, and practical examples to the minimization problem of the Yellow River diversion satisfying other reservoir operation objectives.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.32-33
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• 2018

낙동강 하구의 지형변화를 포함한 제 해양환경은 낙동강 하굿둑이 건설된 1987년 7월 이후로 분기된다. 즉, 낙동강 하굿둑이 건설되기 전에는 낙동강의 작은 하상구배로 담수와 해수가 혼합되는 구역이 현재의 하굿둑 보다 상류에 위치하였으나 하굿둑 건설 이후에는 하굿둑 수문 조작에 따라 방류되는 유출수에 의해 유동 양상이 변화되기에, 낙동강 하굿둑의 방류량을 파악하는 것은 매우 중요하다 하겠다. 이에 본 연구에서는 낙동강 하굿둑 제원, 방류패턴, 하굿둑 주변 강수량, 하굿둑 방류량을 분석하였다. 또한, 낙동강 하굿둑 방류량에 의한 유사량 분석을 수행하여, 낙동강 하류역의 지형변동의 기초자료를 제공하였다. 연구결과, 낙동강 하굿둑 방류량은 최근 13년 동안의 연평균방류량은 $19,274.56{\times}106m^3$이고 일평균 방류량은 $52.81{\times}106m^3$이고 초당평균 방류량은 $611.19m^3$으로 산정되었다. 낙동강 하굿둑 건설 이후 퇴사량과 준설량을 근거하여 계산된 연간 평균 총유사량은 $3,184,405m^3/yr$이고, 낙동강 하굿둑의 경우 연평균 부유사량이 $3,153,995m^3/yr$, 소류사량이 $30,410m^3/yr$이며 소유사량이 부유사량의 약 1.0%로 나타났다.

• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.961-968
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• 2006

Since a small harbor is often located near surf zone areas which have great influences of sediment transport, there is a great possibility that the sediment will be deposited inside of the harbor. The sediment transport occurring around the harbor entrance can't be explained by the wind wave and wave induced current. In this study, it was investigated the mechanism of the entrainment of sediment into a small harbor with permeable breakwater using hydraulic experiments in 3D wave basin. It is found out that the significant sediment entrainment produced when the mode of oscillation in the harbor became the 1st mode. In the case where the incident wave period was shorter than the period that caused higher mode oscillation in harbor, only a little amount of sediment entrainment took place. The vortex shedding from the top of secondary breakwater played very important roll in the entrainment of sediment into the harbor. It is also found that the small jetty attached at the top of secondary breakwater could effectively prevent the entrainment of sediment into the harbor.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1739-1744
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• 2010

The calculation method using the numerical model developed is currently one of the mose required method to predict sediment transport and bed changes in the rivers. Specially, it is real condition that is applying as it is a single sediment transport equation and sediment transport mode mostly without verification process with field data. The sensitivity analysis and calibration process considering the different sediment transport equations and sediment transport modes should be performed for the accurate bed change prediction of the specified study reach using the a model. Through its process, the optimum sediment transport equation and mode for the study reach should be defined. In this study, bed changes for the actual river are computed using the CCHE2D model allowed to select various sediment transport equations and modes. The bed change sensitivity analysis with different ranges of river flow discharge through its process, the optimum sediment transport equation and mode for the study reach should be defined. The bed change simulation with the actual hydraulic condition and the modeling results are compared with the field survey results.