RMA-2 Model Research Articles

하천의 생태시설물 설치에 의한 하상변동 특성 분석

This study intends to conduct a one-dimensional and two-dimensional hydraulic characteristic analysis of the ecological facilities of Jocheon. For this purpose, two field surveys were conducted on hydraulic characteristic data such as longitudinal and cross-sectional data of rivers and roughness coefficient, and boundary conditions were set by establishing flow data for one-dimensional numerical simulation and calculating the starting point of water level. The water level was derived from the results of one-dimensional hydraulic characteristic analysis according to the ｢Jocheon Basic River Plan｣ as input data for the RMA-2 model. Lastly, the riverbed changes in the entire section of the target river and the facility installation section were confirmed and analyzed through SED-2D simulation using the calculated flow velocity. As a result, it was analyzed that the width of the river has a great influence on the flow rate. In additon to this, the concentration of suspended sediment flowing into the upstream has the most influence on the change of the river bed.

Utilizing inactive storage in a dam reservoir during extreme drought periods

The purpose of this study is to suggest a structural plan for improving the utilization of inactive storage in dam reservoirs, to mitigate extreme drought. Inactive storage in the dam is composed of emergency storage and dead storage. The emergency storage can be used in emergencies such as drought. But, in general, the dead storage for sedimentation is not used, even in an emergency. Therefore, we developed a methodology to determine how the dead storage space can be partially used during extreme drought periods when the sedimentation has not occurred yet. We call this partial space in a dam reservoir “drought storage”. An accurate analysis of sediment levels needs to be performed before calculating drought storage, and so the present sediment level in the dam reservoir was estimated using SED-2D linked with the RMA-2 model of SMS. After considering the additional available storage capacity based on the estimated sediment level, drought storage was finally determined. We also predicted future sediment levels after 100 years and suggest the amount of drought storage available in the future. As a result, we found that the available drought storage will be lower in the future compared to present drought storage, due to the gradual increase in reservoir sedimentation over time in the dam. Further research may be needed to effectively reduce sedimentation in order to increase the drought storage capacity.

Control of urban river water pollution is studied based on SMS

With the rapid development of economy and society, environmental pressure is increasing and environmental problems are emerging. The pollution of urban water environment is particularly serious. A large number of river channels are cut off and landfilled, land plants are destroyed and hardened, and domestic and production sewage is directly discharged into river channels, resulting in serious damage to the ecological environment of urban water bodies. In the perspective of ecological environment protection, urban polluted rivers have become the focus of water pollution control. In order to improve the ecological environment of urban water body and ensure the sustainable development of social economy, it is of great significance to study the control of urban river water pollution. In this paper, the methods of data collection, numerical simulation and theoretical analysis are used to study the water pollution control of urban inland rivers. Firstly, the current situation of urban water pollution is understood through data access, and then the hydrological water quality model is established based on RMA2 and RMA4 models in SMS. The main parameters of the model were determined by the method of sensitivity analysis. The results show that RMA2 model with Peclet number of 20 and roughness of 0.045, RMA4 model with diffusion coefficient of 1 and NH 3 -N degradation coefficient of 0.16 d −1 can simulate pollutant diffusion well. This paper uses the water quality model to simulate the water environment of urban inland rivers. The research results show that the water quality model can calculate the water environment capacity and pollutant capacity, so as to obtain the amount of water pollutants to be reduced, and realize the effective control of urban river water pollution. • This paper uses data collection, numerical simulation and theoretical analysis to study the prevention and control of water pollution in urban inland rivers. • This article first understands the current situation of urban water pollution through data access, and then establishes a hydrological and water quality model based on the RMA2 and RMA4 models in the SMS. • In this paper, through the calculation of the water quality model, the urban mainstream water environmental capacity is obtained, and the environmental capacity is allocated to the tributaries.

PENGARUH JUMLAH KRIB TIPE ZIGZAG TERHADAP KECEPATAN ALIRAN PADA SUNGAI KRUENG ACEH

The velocity at the inner turns of the Krueng Aceh river which is ± 100 meters from the Pango Bridge results in the collapse of river banks and endangers public facilities. For this reason, it is necessary to design a construction to protect the river bank. One of the alternatives is to use groyne construction. This study simulated the gropozag type groyne as an alternative form of groyne to be installed in the field. The aim of the study is to see the effect of gropozag type groyne on the river speed using the Surfacewater Modeling System (SMS) program to predict the direction of flow after the installation of the crib. Calibration is performed by determining the relative error value using velocity measurement data. This study uses gropozag groyne type with a length of 2,47 m (6 % B), 3 perpendicular groyne formation placements with an inclination of 10o,20o and 30o towards the upstream and the downstream area in 2 variations, namely 5-unit groynes and 3-unit groynes. The results shows that the RMA2 model obtained results that are close to the measurement value, where the value of the relative error obtained is 7.74% in cross 1 and 6.27% in cross 2. The lengthwise analysis of maximum velocity of 5-unit groynes shows that the maximum velocity occurs at V3 of 4,029 m/sec in the KRA5 formation (10o inclined to downstream of 5 units). Maximum speed of 3-unit groynes at V3 with KTA3 formation (3 perpendicular units) is 3,612 m/s. The number of groynes installed also affects the velocity of the simulation results. The velocity of the 5-unit groynes series is greater than that of the 3-unit groynes series.

Analysis of river bed variation using SSARR and RMA-2 models

Future changes in river bed were predicted under the assumption that flow velocity of past and changes in flow rate at upstream river due to construction of large-scale artificial structures downstream occur in the future. Therefore, the long-term runoff volume from the downstream part of Hosan Stream was estimated using the SSARR (Stream Synthesis and Reservoir Regulation Model). Changes in the river bed were simulated using RMA-2 and SED-2D, which are hydraulic models. As a result, it was found that the river bed variation is significantly affected by the inclusion of sediment in flood flow at upstream. A comprehensive evaluation of above results revealed that the river width has significantly affected flow rate, and the inclusion of sediment in flood flow from the upstream has a huge effect on changes in the riverbed. In this regard, there is a need to devise measures to mitigate future flood damage to artificial structures by reflecting sedimentation trends downstream before the construction of large-scale artificial structures at downstream of river.

The Pongola Floodplain, South Africa – Part 1: Two-dimensional hydrodynamic modelling in support of an environmental flows assessment

The Pongola Floodplain in the Makhathini Flats is an area of low topographic relief between the 1973-commissioned Jozini Dam, and the Usuthu River which borders Mozambique. The floodplain system is characterised by a complex mosaic of meandering river channels, levees, and floodplains interspersed with pans (or depressions) and wetlands. The landmark 1982 study of the floodplain, Man and the Pongolo Floodplain, suggested a pattern of flows to ‘maintain the floodplain’ based on socio-ecological criteria. Since 1998, however, annual releases have been primarily targeted at the needs of recession agriculture and inundation of the floodplain in the Ndumu Reserve. No releases have been specifcally aimed at maintaining the floodplain ecosystem and the services it delivers to support the livelihoods of local communities. In 2013, the Department of Water and Sanitation commissioned an Ecological Reserve study of the Usuthu/Mhlatuze Water Management Area, which incorporates the Pongola Floodplain. This paper describes two-dimensional hydrodynamic modelling using RMA2 to inform this flow assessment. Four computational Pongola Floodplain models have been developed since 1979, including cell-based, one- and two-dimensional approaches. The RMA2 model is based on existing topographical, hydrological and hydraulic information, and was calibrated and verifed for the period 2008 to 2010 using water-level data from the local hydrometric monitoring network. Generally, good replications have been achieved in terms of peaks, rising and recession limbs, recession of ponded pan water-levels, and low-flow river stages. The RMA2 modelling represents an advancement of previous hydrodynamic studies of the floodplain and contributes to an improved understanding of its hydraulic behaviour. Model application was for the 15-year period 1990 to 2004, and simulations included naturalised, present management (2014), and 7 potential dam operational scenarios. The results were post-processed for analyses in the DRIFT DSS, described in the companion paper.

하구폐색저감을 위한 도류제 제원에 관한 연구

본 연구에서는 완경사 하천에 유입하는 지류 하구부 하도폐색현상을 규명하기 위하여 본류하도로 유입하는 합류각이 <TEX>$30^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX>, <TEX>$60^{\circ}$</TEX>, <TEX>$75^{\circ}$</TEX> 형태의 가상하도 합류부의 구조를 설정한 후, 수제의 길이가 본류하도 하폭의 4%, 6%, 8%, 10%에 해당하는 도류제에 대해서 각각의 수리학적 특성을 SMS의 RMA-2와 SED2D 모형을 이용하여 수치해석을 실시하였다. 수치해석 결과에서 설정된 적정 도류제를 낙동강 본류에 유입하는 합류각이 큰 감천 합류부와 합류각이 작은 위천 합류부에 적용하여 유속, 수위, 하상변동 등 수리학적 특성 분석을 통한 하구폐색저감을 위한 도류제 제원을 제시하였다. In this study, virtual confluence of <TEX>$30^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX>, <TEX>$60^{\circ}$</TEX>, <TEX>$75^{\circ}$</TEX> type flowing into main channel was designed to comprehend occlusion phenomenon of the mouth of river, then performed numerical analysis using the RMA-2 and SED2D model of SMS according to application of 40m, 60m, 80m, 100m Training levee corresponding to main channel width ratio. Results of simulations analysis are summarized as follows. Applying appropriate Training levee length determined by numerical analysis results, Training levee dimension for occlusion reduction was studied through the analysis of velocity, water level, bed variation at the Gamchen confluence and Wichen confluence.

사연댐 운영수위 하강에 따른 반구대 암각화지점의 수리학적 특성 분석

본 연구는 세계적 문화유산인 반구대암각화의 침수방지를 위해 사연댐의 운영수위를 하강시키는 것이 반구대암각화 보존에 적정한지를 대곡천의 수리학적 특성을 분석하여 평가하였다. 이를 위해 1차원 하천해석 모형인 HEC-RAS를 이용하여 사연댐 수위 변화에 따른 반구대암각화의 침수높이를 분석 하였고, 반구대암각화 지점의 유속 및 흐름을 2차원 하천해석 모형인 RMA-2를 이용하여 대곡천의 영향을 분석하였다. 수치모의 결과 평수기 유량조건에서 사연댐의 수위변화에 따른 반구대암각화의 침수 높이는 사연댐의 수위가 EL.60.0 m에서 EL.56.5 m까지는 반구대암각화 전체가 침수되었으며, EL.52.5 m일 때는 반구대암각화는 침수되지 않는 것으로 분석되었다. 사연댐의 수위가 EL.52.5 m일 때 20년 빈도에서 반구대암각화는 2.7 m(73%)의 침수가 발생하였고, 200년 빈도시에는 3.47 m(93.8%)의 침수가 발생하는 것으로 분석되었다. 홍수기 유량조건일 때 반구대암각화 지점의 흐름특성 분석결과 사연댐의 수위를 EL.60.0 m에서 EL.52.5 m로 낮출 경우 유속이 약 2.5배 증가하였으며, 최대유속선이 반구대암각화를 지남으로써 유수에 의한 훼손을 증가시키는 것으로 분석되었다. Assesment of hydraulic Characteristics has been carried out of Daegokcheon because Sa-yeon dam water level decline operation for proper due to world cultural heritage edged Bangudae petroglyphs. Analyses on the Dae-gok stream were conducted by changing the water level of the Sa-yeon Dam by using the 1D HEC-RAS numerical model for the inundation of height variations and 2D RMA-2 model for the flow characteristics. As a result of the modeling, if the water elevation on the Sa-yeon Dam is higher than EL.52.5 m, the Bangudae Petroglyphs starts to be flooded. The Bangudae Petroglyphs starts submerging from EL.60.0 m to EL.56.5 m on Sa-yeon Dam. The Bangudae Petroglyphs water level increased by 2.7 m for 20year and 3.47 m for 200year flood frequencies, 73% and 93.8% of the inundation occurs, respectively. As a result of the change on the water level of the Sa-yeon Dam, from EL.52.5 m to EL.60.0 m, the flood flow characterization on the Bangudae Petroglyphs showed that the velocity multiplied by 2.5 times the normal flow. The maximum velocity directly approches the Bangudae Petroglyphs thus, causing damaged.

Mass balance modeling to elucidate historical and continuing sources of dioxin into an urban estuary

Polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxins) are typically found in sediment, water and tissue as in the case of the Houston Ship Channel and Upper Galveston Bay (HSC–UGB) in Texas studied in this research. While hydrodynamic and fate and transport models are important to understand dioxin distribution in the various media, it is difficult to assimilate modeling results into a decision framework without appropriate tools that can aid in the interpretation of the simulated data. This paper presents the development of a mass-balance modeling tool linked to RMA2 and WASP models of the HSC–UGB system for 2002–2005. The mass-balance tool was used to aggregate modeling results spatially and temporally and estimate the relative contribution of sediments to dioxin loading into the Channel in comparison to runoff, deposition, and permitted effluent discharges. The total sediment associated-dioxin load into the system calculated using the mass balance model was 2.34×107ngd−1 (almost 86% of the toxic equivalent load), and the re-deposited load to the sediment from the water column was 1.48×107ng-TEQd−1, such that 8.6×106ng-TEQd−1 or approximately 69% of the average daily dioxin flux is transported between model segments as sediment. The external loads to the system contribute approximately 3.83×106ng-TEQd−1, a value that is an order of magnitude smaller when compared to the contribution from sediment. These findings point to the need for sediment remediation strategies that take into account the spatial locations within the system that serve as sediment sources to dioxin in the water column.

이차원 수치모형을 이용한 준설 탁도플륨의 혼합거동 연구

본 연구에서는 충남 서산에 위치한 부남호에서 준설시 발생하는 탁도플륨의 이송 및 확산과정을 2차원 수치모형인 RMA2 모형과 RMA4 모형을 이용하여 예측하였으며, 다항목수질모니터링시스템(YSI6600EDS)을 이용해 측정한 탁도분포와 비교하였다. 현장조사에서는 부남호에서 준설작업이 진행됨에 따라 인근지점에서의 연직방향 탁도 분포를 측정하였으며 표층에서 거리에 따른 수평방향 탁도 분포를 측정하였다. 부남호 전 구간에 대해서 2차원 흐름해석 모형인 RMA2 모형을 적용하였고, 실제 준설작업이 이루어지는 2호지에 대해서 RMA2 모형과 RMA4 모형을 적용하였다. 준설지점의 초기 농도값에 대한 저수지 내 각 지점에서의 거리에 따른 농도비를 현장측정 결과와 비교한 결과, 수치해석에 의한 탁도플륨의 이송확산 모의 결과는 준설작업에 대한 환경영향 범위를 예측하는 데에 적용될 수 있는 것으로 나타났다. The numerical simulations were performed to analyze the advection-diffusion processes of dredging-induced turbidity plume using RMA2 and RMA4 models in Bunam reservoir, Seosan, Chungnam. Field survey was also performed to measure the turbidity using the multi water quality monitoring system (YSI6600EDS). In the field survey, the vertical and horizontal distributions of the turbidity were measured during the dredging operation in Bunam reservoir. RMA2 model was used to simulate the velocity distributions in both the whole domain and the 2nd part of Bunam reservoir. RMA4 model was also used to simulate the concentration distribution in only the 2nd part of Bunam reservoir, where the dredging work were conducted. The comparison of the simulation results with the field data for the advection-diffusion of the turbidity plume using the concentration ratio concepts shows that the numerical model can be applied to analyze the environmental impact of dredging works.

Two Dimensional Hydrodynamic and Pollutant Transport Modeling of Jiangyin-Xuliujing Reach of Yangtze Estuary

A 2-dimensional hydrodynamic model (RMA2 model) was applied to simulate currents and potential pollutant transport in Jiangyin-Xuliujing reach of Yangtze estuary. The result was compared and validated with a validated 3D model (Delft3D Model). The results indicate that the RMA2 model can achieve the requirements of reproducing and predicting the tidal flow and water levels. Based on RMA2 model simulations, a pollutant transport model (RMA4 model) was established to simulate the transport process of potential pollutant discharge from a sewage treatment plant for risk analysis. This linked hydrodynamic and pollutant transport model can provide the valuable scientific supports for future study of water quality in the Yangtze estuary.

Using an integrated model to track the fate and transport of suspended solids and heavy metals in the tidal wetlands

An integrated two-dimensional depth-average numerical model was developed to simulate hydrodynamics and to track the fate and transport of contaminants in the Erh-Chung Flood Way wetland in northern Taiwan. The model was calibrated and verified with field data collected from Nov. 8, 2002 to April 13, 2003. The RMA2 and TOXIWASP models were configured for the wetland system to model mass transport, suspended sediment as well as heavy metals. Hydrodynamic results from the RMA2 model were used to develop mass transport for the TOXIWASP model in the wetland system. Model results mimic the field data for suspended sediment and heavy metals. Results of model sensitivity analyses show that the partition coefficient is a key parameter for the fate and transport of heavy metals in the wetland system.

2·3차원 모형을 이용한 자연하도 만곡부에서의 흐름특성 연구

In this study, the flow characteristic analysis at the curved-channel of the actual channel section is compared and reviewed using the 2D RMA-2 model and the 3D FLOW-3D model. the curve section with curve rate 1.044 in the research section is analyzed applying the frequency of he project flood of 100 years. According to the result, the issue for the application of the FLOW-3D Model's three-dimensional numeric analysis result to the actual river is found to be reviewed with caution. Also, application of the 3D model to the wide basin's flood characteristic is determined to be somewhat risky. But, the applicability to the hydraulic property analysis of a partial channel section and the impact analysis and forecast of hydraulic structure is presumed to be high. In addition, if the parameters to reflect the vegetation of basin and the actual channel, more accurate topological measurement data and the topological data with high closeness to the current status are provided, the result with higher reliability is considered to be drawn.

Analysis of secondary current effect in the modeling of shallow flow in open channels

The 3D information of a secondary flow evolved in curved or confluent channels, which is usually lost in conventional shallow water models due to the depth-averaging process, can be partially retrieved by incorporating the secondary current velocity profile in the vertical direction. In the present study, the depth-averaged shallow water equations with dispersion stresses were solved by the SU/PG scheme among the various numerical methods of the FEM. In the proposed model, to quantify the strength of the secondary flow, the comprehensive factors such as the deformation of the vertical profile of the streamwise velocity, the roughness coefficient, and the curvature ratio were embedded into the dispersion stress terms. Two sets of experimental data, one with a sharply curved channel by Rozovskii (1961) [40], and the other with a confluent channel by Shumate (1998) [51] were used to validate the proposed model. The computed values of the water surface profile and the depth-averaged velocity across the channel showed good agreement with experimental data, which indicated that secondary velocity profiles were preserved properly. The proposed model was applied to a natural stream with moderate curvature to test the field applicability. The simulation results obtained by the proposed model with dispersion terms matched quite well with the ADCP data, whereas the model without dispersion terms produced excessive velocities at both banks, and the commercial RMA-2 model yielded uniform span-wise velocity distributions at all sections. The analysis of the momentum balance and relative dominance of the secondary current demonstrated that the convection and pressure gradient terms played major roles in achieving equilibrium in momentum equations, and the bottom friction ranked next, followed by the remaining dispersion stresses and viscous term of a similar order. It was also found that the pressure gradient term was the primary factor that triggered velocity redistribution. As the Fr increased, the convective acceleration that formed along the channel curvature was activated as a secondary factor in velocity redistribution, whereas the viscous stress term lost its influence. The bottom friction term had minor exertion on the redistribution mechanism.

하도만곡형상에 따른 수리특성분석

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.

배사구 유입부 흐름 및 하상변동 수치모의를 위한 매개변수 검정 및 민감도 분석에 관한 연구

The bed change analysis near the opening gate of a dam or weir to release deposited sediments have been conducted mostly using the numerical models. However, the use of unverified input parameters in the numerical model is able to produce the different results with natural and real conditions. Also, the bed changes near the opening gate of a dam or weir calculated with a numerical model could be varied depending on the geometry extent included the downstream area with supercritical flow in the model. In addition, the different time steps could provide different results in the bed change calculation, even though other conditions such as input parameters, geometries, and total simulation time were same. Therefore, in this study, hydraulic experiments were performed to validate the eddy viscosity coefficient which is the one of important input parameters in the RMA2 model and relevant to variation of simulation results. The bed changes were calculated using the SED2D model based on flow results calculated in the RMA2 model with the verified and selected eddy viscosity coefficient and also compared with experimental results. The bed changes near the opening gate were underestimated in the numerical model comparing with experimental results except only the numerical case without the modeling section of sediment release pipe and downstream area where the supercritical flow was produced. For the simulation of minimum time steps, different shapes of scour hole were produced in numerical and physical modeling.

2차 요소를 이용한 2차원 상향가중 유한요소모형

본 연구의 목적은 하도의 형상이 불규칙한 자연하천에서 2차원 흐름 특성을 해석하고 예측하기 위해 2차 요소를 이용한 정확하고 효과적인 상향가중 유한요소모형의 개발에 있다. 모형의 개발을 위해 선형 삼각형 요소, 선형 사각형 요소와 혼합요소를 적용하였고 2차 삼각형, 사각형 요소와 혼합요소를 적용하여 모형을 개발하였으며, 지배방정식의 수치적분식으로 Gauss Quadrature 방법을 사용하였다. 개발된 모형의 적용성 검증을 위해 하상융기가 있는 수로, U자형 수로 등에 모의를 실시하여 해석해 및 실측치와 비교 검토하였다. 모의 결과 2차 요소가 선형 요소에 비해 보다 정확한 해를 제공하는 것으로 판단되었으며 2차요소를 적용한 상용모형인 RMA-2 모형과 비교한 결과 본 연구 개발 모형이 보다 정확한 해를 나타내는 것을 확인할 수 있었다. 개발된 모형을 향후 자연하천에 적용할 경우 기존의 모형에 비해 향상된 결과를 얻을 수 있을 것으로 판단된다. The objective of this study is to develop an efficient and accurate quadratic finite element model based on Streamline Upwind/Petrov Galerkin (SU/PG) scheme for analyzing and predicting two dimensional flow features in complex natural rivers. For a development of model, quadratic tin, quadrilateral and mixed elements as well as linear tin, quadrilateral and mixed elements were used in the model. Also, this model was developed through reinforcement of Gauss Quadrature which was necessary to integral of governing equation. Several tests for bottom-rising channel and U-type channel were performed for the purpose of validation and verification of the developed model. Such results showed that solutions of second order elements are better accurate and improved than those of linear elements. Results obtained by the developed model and RMA-2 model are compared, and the results for the developed model were better accurate than those of RMA-2 model. In the future if the developed model is applied in natural rivers, it can provide better accurate results than those of existing model.

자연하천에서 마름/젖음 처리를 위한 격자재구성 기법의 개발 (II): 모형의 적용 및 비교.검토

본 연구의 목적은 마름/젖음 영역을 가지는 복잡한 자연하천에 대해 마름/젖음 처리를 위해 개발된 격자재구성 기법의 적용성을 검토하는 것이다. 자연하천에 대한 모형의 적용성과 검증을 위해 개발된 모형을 마름/젖음 영역을 갖는 한강 구간과 낙동강 구간에 적용하였다. 모의 결과를 실측치와 비교한 결과 실측치와 비교적 잘 일치함을 확인할 수 있었고 상용 모형인 RMA-2 모형의 모의결과와 비교해서도 안정되고 정확한 해를 주는 것을 확인할 수 있었다. 본 연구결과를 오염물질의 이송-확산해석, 토사이송해석 등과 연계되어 해석된다면 하천에서의 흐름 해석 및 생태 수리 분야에 효과적으로 응용될 수 있을 것으로 판단된다. The objective of this study is to examine validation of Grid Reconstruction Method, which is developed to simulate drying/wetting in complex natural rivers with wetting and drying domain areas. To verify application of the developed model, the model was applied to natural rivers with wetting and drying domain areas such as Han river and Nakdong river. The simulation results have shown good agreements with observed data and the results for the developed model were more accurate and improved stability of numerical computation than those of RMA-2 model. If the analysis of contaminant advection-diffusion and sediment transport are performed with the study results, the results can be effectively applied to river flow analysis and ecological hydraulics.

RMA2/RMA4 모형을 이용한 서낙동간 수문연계운영의 수질개선 효과 예측

An objective of this study is as follows: 1) performing sensitivity analysis and parameter estimation of RMA2 and RMA4 models for the West-Nakdong River, 2) drawing up alternatives of gates-operation for water-quality enhancement, and 3) quantitative evaluation of methodology of 'flow-restoration by gates-operation' among 'Comprehensive Plan Improving Water-Quality in the West-Nakdong River(WNR)' with the target water-quality(BOD at Nakbon-N point: below 4.3 mg/L). The parameters for the RMA2 (depth-averaged two-dimensional flow model) and RMA4 (depth-averaged two-dimensional water-quality model) were determined by sensitivity analysis. Result of parameter estimation for RMA2 and RMA4 models is <TEX>$1,000\;Pa{\cdot}s$</TEX> of the eddy viscosity, 20 of the Peclet number, 0.025 of the Manning coefficient, and <TEX>$1.0\;m^2/s$</TEX> of the diffusion coefficient. We have evaluated the effects of water-quality enhancement of the selected alternatives by numerical simulation technique with the models under the steady-state flow condition and the time-variant transport condition. Because of no-resuspension from river bottom and considering BOD as conservative matter, these simulation results slightly differ from real phenomena. In the case of <TEX>$50\;m^3/s$</TEX> of Daejeo-gate inflow, two-dimensional flow pn results result represents that small velocity occurs in the Pyungkang Stream and no flow in the Maekdo River. In the WNR, there occurs the most rapid flow near timhae-bridge. In the WNR, changes of water-quality for the four selected simulation cases(6, 10, 30, <TEX>$50\;m^3/s$</TEX> of the Daejeo-gate inflow) were predicted. Since the Daejeo-Gate and the Noksan-Gate can be opened up to 7 days, it would be found that sustainable inflow of <TEX>$30\;m^3/s$</TEX> at the Daejeo-gate makes BOD in the WNR to be under the target of water-quality.

EFFECT OF AL HUWAYZA MARSH BOUNDARY CONFIGURATION ON THE VELOCITY PATTERNS AND WATER QUALITY DISTRIBUTION

A two-dimensional depth-averaged hydrodynamic model and a two-dimensional waterquality parameters transport model were developed to simulate the characteristics of AlHuwayza Marsh, which is considered the largest and most important marsh in the south ofIraq. The hydrodynamic model for Al Huwayza Marsh was built by using RMA2 model,while the water quality model was built by using RMA4 model. These two models are part ofSurface Water Modeling System, SMS, software package.To investigate the effect of the marsh boundary configuration on the variation of thevelocity pattern and the water quality within the marsh, both of the hydrodynamic and thewater quality models were applied to three cases of boundary configuration of Al HuwayzaMarsh. The first case represents the natural extension of the marsh boundary. The second caserepresents the existing boundary configuration of the marsh, in which the south west of themarsh is bounded by a dyke. The third case represents the Iraqi part of the marsh bounded bythe south west dyke and a dyke along the Iraq-Iranian borders, which when completed willseparate the marsh into two parts.Models runs were based on above cases of Al Huwayza Marsh boundary configurationand topographical survey, hydrological measurements and routing, and water qualitymeasurements carried out by the Center of Rehabilitation of Iraqi Marshlands. Discharges ofall feeders and stages of the outlets are considered for wet, normal, and dry years. Feeder’sseasonal discharges were averaged. High and low concentrations of three selected waterquality parameters of the marsh feeders were adopted in the model runs.Generally, it was found that the flow velocities are relatively high at the inlets andoutlets of the marsh. The construction of the dyke along the Iraqi-Iranian border leads tovariation in the direction of water flow in all portions of the marsh and a great reduction inAsSuwayb River discharge. While, a slight effect was noticed in the mixing process of thefeeders’ water of different concentration in case three compared to other cases