• Journal of Environmental Science International
• /
• v.24 no.4
• /
• pp.359-369
• /
• 2015

This study analyzed the velocimetry of runoff and measured the flood discharge by applying the SIV (Surface Image Velocimetrer) to the daytime and nighttime flow image data with special reference to Seong-eup Bridge at Cheonmi stream of Jeju during the flow by the severe rainstorm on May 27, 2013. A 1000W lighting apparatus with more than 150 lux was installed in order to collect proper nighttime flow image applied to the SIV. Its value was compared and analyzed with the velocity value of the fixed electromagnetic wave surface velocimetry (Kalesto) at the same point to check the accuracy and applicability of the measured velocity of flow. As a result, determination coefficient $R^2$ values were 0.891 and 0.848 respectively in line with the velocity distribution of the daytime and nighttime image and the flow volume measured with Kalesto was approximately 18.2% larger than the value measured with the SIV.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.53 no.2
• /
• pp.9-17
• /
• 2011

Based on the statistical annual report, there are 17,649 reservoirs are operating for the purpose of agricultural water supply in Korea. 58 % of entire agricultural reservoirs had been constructed before 1948 which indicate the termination of required service life and rest of those reservoirs have also exposed to the dam break risk by extreme flood event caused by current ongoing climate change. To prevent damages from dam failure accident of these risky small size dams, it is necessary to evaluate and manage the structural and hydrological safety of the reservoirs. In this study, a simplified evaluation method for hydrologic safety of dam is suggested by using Rational and Creager formula. Hydrologic safety of small scale dams has evaluated by calculating flood discharge capacity of the spillway and compares the results with design frequency of each reservoir. Applicability and stability of suggested simplified method have examined and reviewd by comparing the results from rainfall-runoff modeling with dam break simulation using HEC-HMS. Application results of developed methodology for three sample reservoirs show that simplified assessment method tends to calculate greater inflow to the reservoirs then HEC-HMS model which lead lowered hydrologic safety of reservoirs. Based on the results of application, it is expected that the developed methodology can be adapted as useful tool for small scale reservoir's hydrologic safety evaluation.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2012.05a
• /
• pp.599-603
• /
• 2012

본 연구에서는 부정류 계산 모형을 이용한 확률 홍수량 및 홍수위 산정 방법을 개발하고, 이를 한강 살리기 사업이 진행 중인 남한강 구간에 적용하였다. 우선 한강 살리기 사업 전과 후의 하도에 대하여 부정류 계산 모형을 각각 수립하였으며, 과거 발생한 홍수사상을 조사하였다. 사업 전 모형과 최근에 발생한 홍수사상을 이용하여 모형의 보정 및 검증을 실시하고, 추정된 매개변수를 사업 후의 하도에 대한 모형에 적용하였다. 대상 유역에 과거 발생한 홍수사상을 사업 후 모형으로 모의하여 각 홍수사상 별로 최대 홍수량 및 홍수위를 계산하였다. 이때 최대 홍수량 모의 결과들을 빈도해석 대상 자료군으로 사용하여, 연최대치 계열이나 부분 시계열에 대하여 빈도해석을 통하여 확률 홍수량을 산정할 수 있다. 본 연구에서는 장기간의 관측자료의 확보가 어려운 국내의 현실을 고려하여, 부분 시계열의 빈도해석 방법을 사용하여 확률 홍수량을 산정하였다. 다음으로 부정류 계산모형의 모의 결과인 최대 홍수량 및 홍수위 자료를 회귀분석하여 수위-유량 관계식을 유도하고, 각 빈도별 확률 홍수량을 관계식에 대입하여 확률 홍수량에 대응하는 확률 홍수위를 산정하였다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2012.05a
• /
• pp.387-391
• /
• 2012

경인아라뱃길은 인천 서구 오류동과 서울 강서구 개화동을 연결하는 뱃길로 선박의 항해를 위한 주운수로와 두 개의 갑문으로 이루어져 있다. 홍수시 굴포천 상류유역의 홍수량이 열결 수로를 통하여 서해로 배제되며, 굴포천 하류유역의 경우 연결 암거를 통해 홍수량 일부를 서해로 방류한다. 본 연구에서는 2011년 발생한 7월 호우사상에 대하여 경인아라뱃길 유역의 홍수량 및 홍수위의 변화를 검토하였다. 강우-유출 모의는 Clark 유역추적법을 적용하여 14개의 소유역별 홍수량을 산정하였으며, Muskingum-Cunge 방법을 적용하여 하도추적을 수행하였다. 소유역에 대한 홍수 도달시간과 저류상수는 각각 Kirpich 방법과 Russel 공식을 이용하였고, 유출곡선지수값은 AMC-III를 적용하였다. 강우자료는 서울기상청과 인천기상대의 2011년 7월 호우사상을 사용하였으며, 하도의 홍수위 분석은 부정류 해석방법을 이용하였다. 분석 결과, 경인아라뱃길의 각 지점 홍수위는 제방고보다 전체적으로 낮았다. 100년 빈도 홍수량에 대해서 홍수방어가 가능한 경인아라뱃길은 2011년 7월말 호우사상에 대하여 안전한 것으로 판단된다.

• Current Research on Agriculture and Life Sciences
• /
• v.2
• /
• pp.77-90
• /
• 1984

Results investigated backwater phenomena at Geumho river basin to get a basic data for Daegu basin area development plan are as the follows. 1. It is a A=0.35 L 1.848 (r = 0.97), the relationship between basin area and river length at Geumho river. 2. Dividing the rainfall of Geumho river basin as two parts, a first half rainfall and a second half rainfall, the amount of a first half rainfall appeared 57.5% comparison with total rainfall. 3. The maximum flood discharge appeared 12 hrs. continuous rainfall rather than 24 hrs. continuous rainfall. 4. Results investigated backwater phenomena from Geumho II bridge to chungchun appeared the rising water level of 69 cm, 55 cm, 44 cm, at section III in the starting point water level of 1.8 m, 2.4 m, 4.0 m respectively. 5. Results investigated backwater phenomena by the flood water level appeared a similar form. There was a average rising water level of 30 cm at section III. At the results of this computation, it was confirmed that section III was affected the highest backwater phenomena among the observed river reaches in Geumho river. In addition, this paper should be given a assistance to decide a economic and safe section in construction of bank of river and estuary barrage.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.38 no.6
• /
• pp.819-829
• /
• 2018

The bed change survey was carried out and its tendency was analyzed at the downstream of the Singok Submerged Weir in the Han River Estuary (HRE). In order to focus on the bed change in the low flow channel, we calculated the mean bed elevation based on the bankfull discharge. Thanks to the amount of bed changes calculated by using the 'averaged bed', we could compare the riverbeds of various periods with consistent criteria. In the HRE, revealed was the bed change cycle between degradation by flood and aggradation by tide at the non-flood season.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.167-167
• /
• 2020

Annual sediment deposition in reservoirs behind weirs poses flood risk, while its accurate prediction remains a challenge. Sediment management by hydraulic flushing is an effective method to maintain reservoir storage. In this study, an integrated approach to predict sediment inflow and sediment flushing simulation in reservoirs is presented. The annual sediment inflow prediction was carried out with Artificial Neural Networks (ANN) modelling. RESCON model was applied for quantification of sediment flushing feasibility criteria. The integrated approach was applied on Sangju Weir and also on estuary of Nakdong River (NREB). The mean annual sediment inflow predicted at Sangju Weir and NREB was 400,000 ㎥ and 170,000 ㎥, respectively. The sediment characteristics gathered were used to setup RESCON model and sediment balance ratio (SBR) and long term capacity ratio (LTCR) were used as flushing efficiency indicators. For Sangju Weir, the flushing discharge, Q_f = 140 ㎥/s with a drawdown of 5 m, and flushing duration, T_f = 10 days was necessary for efficient flushing. At NREB site, the parameters for efficient flushing were Q_f = 80 ㎥/s, T_f = 5 days, N = 1, El_f = 2.24 m. The hydraulic flushing was concluded feasible for sediment management at both Sangju Weir and NREB.

• Journal of Wetlands Research
• /
• v.19 no.1
• /
• pp.30-36
• /
• 2017

SS(Suspended Solid) concentration by soil erosion into river at normal and flood season should be measured. However, to present the variation of SS due to various development project such as EIA(Environmental Impact Assessment), River Master Plan, and so on, it is necessary to estimate not measure SS, but there are not exist how to estimate SS. In the present study, therefore, we propose the hydrologic method of estimating SS concentration using the results of particular frequency flood discharge and sediment discharge by RUSLE method. SS consists of silty and clay soil and colloid particle etc. However, in the present study, silty and clay soils of sediment discharge except send set up SS standards. The flow discharge to estimate SS concentration are 1~2 years for normal season, 30~100 years for flood season. Meanwhile, analysis software for probable rainfall uses Fard2006, probable rainfalls under 2-year frequency are estimated using rainfall data and frequency factor of Gumbel distribution. The results of estimating SS concentration using runoff volume by sediment and flow discharges of silty and cray soils as above method show that reliable level of SS concentration is considered in predevelopment of natural condition and under development of barren condition. Especially, SS concentration takes notice that the value of sediment discharge makes a huge difference according to channel slope, it was confirmed that the value obtained by dividing the SS concentration by the channel slope is relatively constant even though the topographical factors are different. Therefore, if the present study will be proceeded for various watersheds, it will be developed as estimation method of SS concentration.

• Journal of Korea Water Resources Association
• /
• v.49 no.4
• /
• pp.347-359
• /
• 2016

Flow input from the basin will not remain the same as before due to climate changes. Since the predictions on river discharge due to climate change is given by scenarios, various discharge scenarios were prepared in this study. For a long term and reach prediction, semi-two dimensional sediment transport model, GSTARS, was used. The flood water surface elevations predicted by GSTARS model were analysed statistically and it was concluded that the model is applicable for the South Han River. Three stream tubes is the most suitable to simulate two dimensional river geometric change River geometric changes. For sediment load computation, Ackers and White equation and Yang equation were resonable. River will become narrower regardless of discharge variation, more discharge results in deeper channel.

• Journal of Environmental Science International
• /
• v.25 no.4
• /
• pp.491-504
• /
• 2016

This study, examines the flow characteristics of upstream channel depending on water gate operation of Nakdan Multi-fuctional weir. The specific purpose of this study are to simulate the variation of flow velocity depending on the operation of the weir using 1-dimensional hydraulic model, HEC-RAS, and compare it with observed velocity. For discharge conditions from $50m^3/s$ to $3,500m^3/s$, it is observed that the velocity of upstream channel is almost constant, whereas for probability flood discharge, the velocity and froude number are increased as the discharge values are increased. The velocity values for downstream boundary condition EL, 40.0 m are more decreased than those for EL. 40.5m. From comparison on the variation of water stage depending on water gate operation, it is observed that the stage values are almost constant for discharges below $300m^3/s$, whereas 5 cm to 20 cm for discharges over $700m^3/s$. Flow velocity at streamflow gauging station. Nakdong, is decreased by more than 875% after installing the weir. The results obtained from this study indicate that the velocity of upstream channel is decreased and the discharge and velocity of downstream channel are significantly varied after installing the weir.