Nakdong River Estuary Barrage Research Articles

Complementary Modeling Approach for Estimating Sedimentation and Hydraulic Flushing Parameters Using Artificial Neural Networks and RESCON2 Model

Accurate prediction of reservoir sediment inflows (Min) and adaptation of feasible sediment management strategies pose challenges in water engineering. This study proposed a two-stage complementary modeling approach for comprehensive reservoir sediment management. In the first stage, artificial neural network-based models provide real-time Min predictions using water inflow, water head, and outflow as input parameters. In the second stage, the parameter estimation method of the RESCON model is applied to hydraulic flushing in a reservoir. This approach was applied to the Sangju Weir and Nakdong River Estuary Barrage (NREB) in South Korea. Results from the RESCON model revealed that hydraulic flushing was effective for sediment management at both the Sangju Weir reservoir and the NREB approach channel. Efficient flushing at the Sangju Weir required a flushing discharge of 100 m3/s for 6 days and 40 m of water head. Efficient flushing at the NREB required a flushing discharge of 25 m3/s for 6 days with 1.8 m of water-level drawdown. The proposed approach is expected to prove useful in reservoir sediment management.

Study on the Characteristics of the Hydraulic Environment in the Downstream Area According to the Discharge of Changnyeong-Haman Weir

Kim, T.W.; Kim, Y.J.; Cho, W.C.; Park, B.W., and Yoon, J.S., 2019. Study on the characteristics of the hydraulic environment in the down-stream area according to the discharge of Changnyeong-haman weir. In: Lee, J.-L.; Yoon, J.S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp.151-155. Coconut Creek (Florida), ISSN 0749-0208.This study refined the reproducibility of a stream cross section of the Nakdong River using the Modified EFDC model and examined the salt water flow from the external sea to the river upstream according to the changing gate open rate of Nakdong River estuary barrage and the influent flow and tide level conditions in the Changnyenong-Haman Weir using a numerical model. Furthermore, numerical simulations were conducted and the hydraulic characteristics were examined to investigate the flushing effect according to the changing discharge of the Changnyenong-Haman Weir in the event of a salt wedge.

The Investigation of Sea Water Intrusion Length on Opening of Nakdong River Estuary Barrage Using Numerical Simulation Model

The Investigation of Sea Water Intrusion Length on Opening of Nakdong River Estuary Barrage Using Numerical Simulation Model

Numerical modeling of sedimentation control scenarios in the approach channel of the Nakdong River Estuary Barrage, South Korea

The effects of sedimentation reduction at the Nakdong River Estuary Barrage (NREB) in Korea were quantitatively analyzed with respect to different sediment control methods using the calibrated and validated two-dimensional model. The countermeasures of sediment dredging, sediment flushing, channel geometry change, and a combination of flushing and channel geometry change were examined for the approach channel of the NREB. The flood event and channel geometries of the 3.8km section upstream of the NREB surveyed before and after dredging in 2007 were used for modeling conditions. As a result, the half of sediments dredged in 2007 could be eliminated naturally by floods without dredging. The numerical simulation of sediment flushing indicated that the deposition height decreased in the entire simulation section with the minimum and maximum reductions from 0.3m to 1.3m in deposition height. The channel contraction method produced quantitatively the largest amount of sedimentation reduction and sediment flushing and dredging followed. Sedimentation reduction by a combination of flushing and channel contraction was up 10% compared to the individual method of channel contraction.

PLC(Programmable Logic Controller)와 공중통신망을 이용한 하천수위감시시스템 구축 사례 연구

A river water level monitoring system which prevents salt water damages and effectively excludes floods has been developed to contribute efficient operation of Nakdong river estuary barrage. The system can be used for monitoring upstream conditions more quickly and do appropriate responses over changes. Telemetry and telecontrols using PLCs have been built at the three sites that directly influence on the operation of barrage gates, and are linked to Nakdong river estuary barrage’s IOS (Integrated Operation System) through public communication networks. By using PLC, the system can achieve even higher reliability and versatility than before as well as easy management. By power control devices, we can remotely control the power of PLCs to treat the minor troubles instantly without going on-sites. The power control devices also save data in preparation for the cases of communication failures. The system uses ADSL (FTTH) as a main network between SCADA server and PLCs, and CDMA (M2M) as a secondary network. In order to compensate security vulnerabilities of public communication network, we have installed the VPNs for secure communication between center and the observation stations, just like a dedicated network. Generally, river water level observations have been used custom-manufactured remote terminals to suit their special goals. However, in this case, we have established a system with open architecture considering the interface between different systems, the ease of use and maintenance, security, price, etc.

낙동강 하굿둑의 배수문 증설에 따른 통합운영시스템의 구축 사례에 대한 연구

Due to the Four Major Rivers Restoration Project, Nakdong River Estuary Barrage’s designed flood quantity has been largely increased, and this has caused to construct several drainage gates at the right side of Eulsukdo island to secure the safety of downstream river area. For successful functioning of Nakdong River Estuary Barrage, such as flood control, disaster prevention, and the securing of sufficient water capacity, drainage gates at the both sides of island have to operate systematically and reliably. To manage this under restricted personnel and resources, we have implemented the IOS (Integrated Operation System) by integrating previous facilities and resources via information and communication technologies. The IOS has been designed to have higher availability and fault tolerance to function continuously even with the partial system’s failure under the emergency situation like flood. Operators can use the system easily and acknowledge alarms of facilities through its IWS (Integrated Warning System) earlier. Preparing for Integrated Water Resources Management and Smart Water Grid, the architecture of IOS conformed to open system standards which will be helpful to link with the other systems easily.

SWAT 모형을 이용한 낙동강 유역의 장기 유출에 따른 유사량 분석

Abstract Sediment discharge by long-term runoff in the Nakdong River watershed should be predicted for the maintenance and management of the Nakdong River newly changed by the four major river restoration project. The data establishment by the analysis of runoff and sediment discharge using the long-term watershed model is necessary to predict possible problems by incoming sediments and to prepare countermeasures for the maintenance and management. Therefore, sediment discharges by long-term runoff in the main points of the Nakdong River were calculated using SWAT(soil and water assessment tool) model and the relations and features between rainfall, runoff, and sediment discharge were analyzed in this study. As a result of sediment discharge calculation in the main points of the Nakdong River and tributaries, the sediment discharge at the outlet of the Naesung Stream was greater than the Jindong Station in the Lower Nakdong River from 1999 to 2008 except the years with low precipitation. The sediment discharge at the Nakdong River Estuary Barrage (NREB) was corresponding to 20% of the Jindong Station which is located about 80 km upstream from NREB.

Analysis for the effectiveness of sediment dredging in the approach channel at the Nakdong River estuary barrage

The upstream channel of the Nakdong River Estuary Barrage (NREB) has experienced sedimentation problems requiring annual dredging operation after the construction. The main purpose of sediment dredging is to prevent flooding during late summer. Numerical simulation and volume analysis using field surveying data for the Lower Nakdong River have been conducted to quantify the bed changes with and without dredging operation and to analyze the effectiveness of dredging at the NREB. As a result, it is presented that the bed change rate (sedimentation rate) after dredging is much faster than the bed condition without dredging. The water surface rising of the maximum 10 cm was generated in case the dredging was not considered in the modeling. Volumetric analysis of bed changes using field surveying data presented that 41 percent of total sediment erosion was eliminated by natural flushing and 59 percent was dredged in the field. Because it is noticeable that dredged section is redeposited rapidly after dredging during low flow through the 2D simulation, it is expected that most of total sediment erosion (at least more than 41% of total sediment erosion) is caused by natural flushing due to the floods. Therefore, it is highly recommended to use natural flushing or intentional sluicing techniques for sedimentation control methods at the NREB.

낙동강 하류의 퇴사저감을 위한 하폭축소방법이 홍수위변화 및 하상변동에 미치는 영향 분석

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.

Sediment Flushing at the Nakdong River Estuary Barrage

The Nakdong River Estuary Barrage (NREB) prevents salt-water intrusion but causes sedimentation problems in the Lower Nakdong River in South Korea. Its mitigation requires mechanical dredging to maintain the flood conveyance capacity during typhoons. This analysis focuses on the possibility of replacing mechanical dredging with sediment flushing through gate operations changes at NREB. The new approach first defines sediment flushing curves as a function of river stage and discharge. The feasibility of flushing is then assessed from the comparison of the flushing curves with the flow duration curves. The detailed analysis of long-term simulations using a quasi-steady numerical model provides detailed simulation results. The model applications from 1998 to 2003 incorporate tidal effects at 15-min intervals and also include major floods caused by typhoons Rusa in 2002 and Maemi in 2003. Accordingly, about 54% of the mean annual dredging volume could be eliminated by sediment flushing at NREB. The model also quantified the flood stage differences for sediment flushing operations with and without dredging. The resulting stage difference at NREB during floods would be less than 30 cm.

낙동강 하구 염분 농도 분포에 관한 연구

The purpose of salinity intrusion due to numerical simulation is analaysis for saline intrusion to the upstream channel in Nakdong River Estuary Barrage(NREB) to get enough fresh water. Conditions that occur salinity intrusion affect by tidal distribution at seas, so salinity concentration changes according to tidal phenomenon. Making this connection cleary can help preventing salinity intrusion. In this study, estimating salinity intrusion to the upstream channel in NREB using EOMSED model, we reexamine NREB`s existence. Comparison is also made with observing data. In result, when inflow discharges at is more similar with respect to observing data than at ECOMSED model. Thus, estimations are more precise at little discharges than lots of discharges.

하구둑에서의 하폭축소 방법을 이용한 퇴사저감 효과 분석

In this study, the methods of sedimentation reduction for the estuary barrage were analyzed using the CCHE2D bed change model. Especially, the effectiveness of sediment dredging currently applied in the field was evaluated quantitatively and also the channel contraction method which is a substitute method was analyzed for the Nakdong River Estuary Barrage (NREB). The numerical model was calibrated and validated for the sediment transport equations and transport modes. In the NREB case, the Ackers and White formula and bed load type was the most similar to the field condition. As a results of the dredging simulation, there was the sedimentation reduction effect of 0.2 m in the bed changes. Furthermore, the analysis result of the channel contraction method represented that the sedimentation reduction effects of the average 0.4 m and the maximum 2.0 m were produced.

HEC-6 모형을 이용한 유사량 공식에 따른 하상변동 민감도 분석 - 낙동강 하류를 대상으로

In this study, the sensitivity analysis of bed changes due to the various sediment transport equations have been conducted for 80 km reach of the Lower Nakdong River using the HEC-6 which is one dimensional numerical model. The bed elevation changes according to the different sediment transport formulas were compared and analyzed quantitatively. As a result of the numerical simulation, the final bed elevation calculated by Engelund and Hansen(1967), Ackers and White(1973), and Yang(1979) formulas was similar to one another in configuration. The bed change simulated by Engelund and Hansen(1967) were greatest among them, for example, 5.5 m deposition and 2.9 m erosion for 100 years. Also, in the case of Toffaleti (1969) equation, the maximum bed deposition of 8.04 m after 100 years was induced at the 73 km location upstream of the Nakdong River Estuary Barrage. Meyer-Peter-M<TEX>$\ddot{u}$</TEX>ller(1948) and Wilcock(2001) formulas produced the deposition only at the upstream end and there was little bed change in the downstream area. The unreal bed configuration of continuously up and down pattern was simulated by Laursen(1958) transport equation.

낙동강하구둑 상류 접근수로에서의 유사량 공식 및 유사 이송형태에 따른 하상변동 수치모의에 관한 연구

본 논문에서는 2차원 하상변동 수치모형인 CCHE2D 모형을이용하여 유사량 공식과 유사이송형태별 이류-확산 방정식의 선택이 하상변동 수치모의결과 값에 미치는 영향을 분석하고 실제 현장자료와 비교하였다. 또한 이러한 분석을 기초로 낙동강하구둑 상류 접근수로에서의 최적의 유사량 공식과 유사 이송형태별 이류-확산 방정식을 제안하였다. 낙동강하구둑 상류 접근수로에 대해 Ackers and White와 Engelund and Hansen의 유사량 공식과 소류사와 부유사 유사 이송형태에 따른 이류-확산 방정식을 각각 다르게 적용하여 모의한 결과, Engelund and Hansen 공식을 적용한 경우에는 Ackers and White 공식을 적용한 경우와 비교했을 때, 평수 및 홍수 조건에서 모두 하상변동량이 거의 없는 것으로 나타났다. 또한 Ackers and White 공식으로 2002년에 발생한 실제 수문사상을 적용하여 하상변동 모의한 결과, 소류사 이송형태의 이류-확산 방정식을 적용한 모의결과가 부유사 이송형태를 적용했을 경우 보다 실제 하상변동에 더 근접한 것으로 나타났다. The effects of the selection for sediment transport equations and advection-diffusion equations according to different sediment transport modes on the modeling results of bed changes were analyzed using the CCHE2D and compared with field data in this paper. The most suitable sediment transport equation and sediment transport mode for advection-diffusion equation were suggested for the upstream approached channel of the Nakdong River Estuary Barrage. The bed changes simulated by the Engelund and Hansen formula were very small in the modeling case for the low and high flow discharges compared with the case of the Ackers and White formula. Also, the numerical modeling with the actual hydraulic event in 2002 presents that the bed change result with the bed load transport type for advection-diffusion equation was close to the field measurement more than the suspended load type.