• Water Engineering Research
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• 제6권3호
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• pp.113-122
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• 2005

Periphyton is known to be one of major primary producers for river ecosystem. While the growth of periphyton usually observed on the stone surface in gravel river, the large growth of periphyton is sometimes seen even in sand river with relatively small river discharge. In the present study, field observations and numerical simulations were performed to investigate the growth of periphyton in sand river. In the field observation, the growth of periphyton on fixed sand bed was measured weekly. The results of the field observations show that the large growth of periphyton occurs in sand river until the bed material sands have not moved. An integrated numerical simulation model is presented to describe the growth of periphyton at observed river reach, and a series of numerical simulations were performed to study the effect of river discharge on growth of periphyton in the sand river. The results of the numerical simulations show that the net primary production of periphyton decreases with the river discharge. These results suggest that the reduction of river discharge at ordinary water stage strongly affects the primary productivity of periphyton even in sand river.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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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.

• 한국농공학회지
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• 제22권4호
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• pp.96-107
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• 1980

This study is carried out to estimate the rate of sediment transportation both to measure the amount of suspended and bedload sediment that moves on or near the river bed and passes through the cross section of a river in unit time, with suspended and bed load samplers used for the Milyang river and to determine the most satisfactory and convenient formula of some formulas for sediment discharge by comparing the measured rate with the calculated rate. The results of this study are summarized as follows; 1) The interrelationship (1) between the total discharge and the total sediment discharge (2) between discharge and suspended sediment load and (3) between discharge and bed load in the Milyang river are (1) i) 4$\leq$Q$\leq$100 C.M.S. Qr=0. 00272 Q0.70 (kg/sec) ii) 150$\leq$Q$\leq$800 C.M.S. Qr=0. 4807 Q0.46 (kg/sec) (2) Qs~=0. 07576 Q1.02 (kg/sec) (3) QB=0. 00957 Q0.44 (kg/sec) 2) The rate of suspended sediment load to total sediment discharge is found to be about; 99%. The suspended load is shown to be almost wash load which consists of silt and clay. 3) The relation between the total discharge and the suspended sediment load that are measured at three medium and small rivers in Korea is Qs=0. 13831 Q0.97 (kg/sec) 4) Brown's formula is determined to be the most convenient formula for application and comparison with observed data obtained for the Milyang river.

• 물과 미래
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• 제18권4호
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• pp.327-333
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• 1985

본 연구에서는 하구역에 이안제를 설치했을 경우 하천류가 없고 파가 경사져서 입사해 올 때 하구 및 제체 주변에 발생하는 해빈류의 흐름상태를 수치계산에 의해서 구하고 고정상 수리실험을 통하여 얻은 결과와 비교해서 본 수치모델의 타당성을 검증하였다. 또한 이동상 수리실험을 통하여 하구 및 이안제 주변에서 일어나는 지형변화를 검토하여 하구폐새 방지대책으로서 이안제공법의 효용성을 확인하였다.

• 대한토목학회논문집
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• 제32권1B호
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• pp.1-7
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• 2012

본 연구에서는 준 2차원 수치모형인 GSTARS를 이용하여 형산강의 하상변동모의에 적합한 최적 유사량공식을 산정하고자 하였다. 모형의 검보정을 위한 유사량, 하상재료 및 하천지형자료를 현장조사를 통해 취득하였다. 현재까지 널리 적용되는 유사량 공식들에 대하여 장기하상변동 모의결과의 실측치에 대한 평균오차, 상대오차, 평균제곱오차, 상대제곱근오차, 불일치율, 그리고 Nash-Sutcliffe 효율계수를 비교한 결과, Laursen(1958)공식이 형산강의 장기하상 변동을 모의하기 위한 가장 적합한 유사량공식으로 판단되었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.63-63
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• 2021

Bed shear stress is important variable in river flow analysis. The bed shear stress has an effects on bed erosion, sediment transport, and mean flow characteristics. Quadratic formula to estimate bed shear stress is widely used, 𝜏=𝜌c_fu|u| in which friction coefficient, c_f, needs to be assigned to numerical models. The aim of this study is to estimate Chezy coefficient using bathymetry data measured by ADCP. Bed form geometry variables will be estimated form bed profile, then Chezy coefficient will be determined using estimated bed form geometry variables in order to set friction coefficient to numerical model. From the probability density function obtained from the bathymetry data, Chezy coefficient will be randomly generated since Chezy coefficient is not uniform over the space and it does not depend on spatial variables such as water depth and distance from river bank. Numerical test will be performed to find to demonstrate randomly extracted Chezy coefficient is appropriate. The result of this study is valuable in that the friction coefficient is estimated in consideration of the bed profile, and as a result, uncertainty of the friction coefficient can be reduced.

• Journal of Forest and Environmental Science
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• 제15권1호
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• pp.89-97
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• 1999

산지계류에 서식하는 수서곤충의 종류와 서식조건에 대한 기초자료를 얻기 위해 강원대학교 산림과학대학 부속연습림내의 봉명천을 대상으로 수서곤충, 음이온 및 하상재료를 파악한 결과는 다음과 같다. 1. 각 지점별 수서곤충의 종다양도, 종풍부도 및 균등도는 사방댐의 상류역이 하류역보다 높게 나타났다. 2. 음이온은 A, B, C, D 및 E 지점 모두 유사하였지만 하류역인 F지점에서는 상류역에 비해 최소 1.5배에서 최대 89배 이상의 이온이 검출되었다. 3. 하상재료는 상류역이 하류역보다 입경이 크게 나타났으나, 사방댐 직하부는 사방댐에 의해 하류역보다 자갈의 구성도가 높게 나타났다. 4. 수서곤충의 수는 음이온 농도에 반비례하였고, 하상재료의 크기와는 정비례하였으며, 특히 호박돌의 분포도에 크게 영향을 받은 것으로 나타났다.

• 한국수자원학회논문집
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• 제48권1호
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• pp.1-8
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• 2015

본 논문에서는 지난 20여 년간의 낙동강 하상변동 자료와 준설 및 골재채취 자료, 그리고 지류로부터 유입되는 유사량 관측 자료 및 수치모의 자료 등을 조사, 검토, 분석하여 4대강살리기 사업 전의 낙동강 하도에서의 개괄적인 유사수지 특성을 분석하였다. 4대강살리기 사업 전 낙동강 하도의 유사수지분석 결과, 유역에서 하도로 유입된 유사량은 $2,100,000m^3/yr$이며 낙동강으로부터 유출 또는 준설된 유사유출 총량은 $10,180,000m^3/yr$인 것으로 나타났다. 따라서 유사수지 분석을 통해 산정된 낙동강 하도에서의 하상변동량은 $-8,080,000m^3/yr$으로 하상이 침식된 것으로 나타났으며 이는 실제 하도측량 자료 분석을 통해 도출된 낙동강 본류의 자연적 그리고 인위적인 하상변동량($-8,300,000m^3/yr$)과 유사한 것으로 나타났다.

• 한국방재학회 논문집
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• 제1권3호
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• pp.93-102
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• 2001

본 연구에서는 HEC-6 모형을 이용하여 태화강 본류하도 하구부에 위치한 방사보의 영향에 따른 하상변동특성을 분석 검토함으로서, 향후 태화강 하도종합개발계획 수립시에 효과적으로 이용할 수 있도록 하였다. 하상변동특성 분석에 필요한 유량 조건은 태화강 하천정비기본계획수립에서 검토된 풍수량, 홍수량 및 계획홍수량 조건을 이용하였다. 먼저, 하상변동폭에 대한 분석 결과, 삼호교 하류 하도구간에서는 유하유량이 클수록 세굴과 퇴적이 활발히 진행되고 있으나 삼호교 상류 하도구간에서는 큰 변동이 없는 것으로 분석되었다. 다음으로, 유사이송능을 검토한 결과, 유하유량이 클수록 유사이송능은 큰 값으로 추정되었으나 계획홍수량 유하시 방사보 철거전후의 태화강 하구부의 유사이동능은 큰 차이가 없는 것으로 분석되었다. 따라서, 방사보 철거로 인한 토사유입량 감소대책을 고려하여 태화강 하류부에서 유입되는 동천지류의 최하류부에 하천유지용수 확보와 태화강으로의 유사량 유입을 감소시키기 위하여 적절한 수리 구조물을 설치한다면 방사보 제거 후에도 태화강 최하류부의 유사량 퇴적을 감소시키는 좋은 방안이 될 것으로 판단된다.

• 한국환경과학회지
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• 제20권5호
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• pp.555-564
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• 2011

This study examines the potential restoration of abandoned channels of the Mangyeong River in South Korea. To analyze the morphological changes and equilibrium conditions, a flow duration analysis was performed to obtain the discharge of 255 m3/s with a recurrence interval of 1.5 year. It is a gravel-bed stream with a median bed diameter of 36 mm. The reach-averaged results using HEC-RAS showed that the top width is 244 m, the mean flow depth is 1.11 m, the width/depth ratio is very high at 277, the channel velocity is 1.18 m/s, and the Froude number is also high at 0.42. The hydraulic parameters vary in the vicinity of the three sills which control the bed elevation. The total sediment load is 6,500 tons per day and the equivalent sediment concentration is 240 mg/l. The Engelund-Hansen method was closer to the field measurements than any other method. The bed material coarser than 33 mm will not move. The methods of Julien-Wargadalam and Lacey gave an equilibrium channel width of 83 m and 77 m respectively, which demonstrates that the Mangyeong River is currently very wide and shallow. The planform geometry for the Mangyeong River is definitely straight with a sinuosity as low as 1.03. The thalweg and mean bed elevation profiles were analyzed using field measurements in 1976, 1993 and 2009. The measured profiles indicated that the channel has degraded about 2 m since 1976. The coarse gravel material and large width-depth ratio increase the stability of the bed material in this reach.