scholarly journals Sediment Transport Mechanisms in a Lagoon with High River Discharge and Sediment Loading

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1970 ◽  
Author(s):  
Jovita Mėžinė ◽  
Christian Ferrarin ◽  
Diana Vaičiūtė ◽  
Rasa Idzelytė ◽  
Petras Zemlys ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Transport Model ◽  
Suspended Sediments ◽  
Sediment Dynamics ◽  
Strong Wind ◽  
Sediment Distribution ◽  
Holistic View ◽  
Coastal System ◽  
Sediment Transport Model

The aim of this study was to investigate the sediment dynamics in the largest lagoon in Europe (Curonian Lagoon, Lithuania) through the analysis of in situ data and the application of a sediment transport model. This approach allowed to identify the propagation pathway of the riverine suspended sediments, to map erosion-accumulation zones in the lagoon and calculate the sediment budget over a 13-year-long simulation. Sampled suspended sediment concentration data are important for understanding the characteristics of the riverine and lagoon sediments, and show that the suspended organic matter plays a crucial role on the sediment dynamics for this coastal system. The numerical experiments carried out to study sediment dynamics gave satisfactory results and the possibility to get a holistic view of the system. The applied sediment transport model with a new formula for settling velocity was used to estimate the patterns of the suspended sediments and the seasonal and spatial sediment distribution in the whole river–lagoon–sea system. The numerical model also allowed understanding the sensitivity of the system to strong wind events and the presence of ice. The results reveal that during extreme storm events, more than 11.4 × 106 kg of sediments are washed out of the system. Scenarios without ice cover indicate that the lagoon would have much higher suspended sediment concentrations in the winter season comparing with the present situation with ice. The results of an analysis of a long-term (13 years) simulation demonstrate that on average, 62% of the riverine sediments are trapped inside the lagoon, with a marked spatially varying distribution of accumulation zones.

scholarly journals Experimental validation of a cohesive suspended sediment transport model for two Mexican rivers

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Juan Antonio García-Aragón ◽  
Klever Izquierdo-Ayala ◽  
María Mercedes Castillo-Uzcanga ◽  
Laura Carrillo-Bibriezca ◽  
Humberto Salinas-Tapia
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Experimental Validation ◽  
Transport Model ◽  
Suspended Sediment Transport ◽  
Sediment Transport Model

scholarly journals Large-scale suspended sediment transport and sediment deposition in the Mekong Delta

2014 ◽  
Vol 18 (8) ◽  
pp. 3033-3053 ◽  
Author(s):  
N. V. Manh ◽  
N. V. Dung ◽  
N. N. Hung ◽  
B. Merz ◽  
H. Apel
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Large Scale ◽  
Transport Model ◽  
Mekong Delta ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Mineral Fertilizers ◽  
Suspended Sediment Transport ◽  
Extreme Flood

Abstract. Sediment dynamics play a major role in the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains, and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment deposition in the whole Mekong Delta. To this end, a quasi-2D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for 2 validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition is differentiated from Kratie at the entrance of the delta on its way to the coast. The main factors influencing the spatial sediment dynamics are the river and channel system, dike rings, sluice gate operations, the magnitude of the floods, and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, annual sediment loads reaching the coast vary from 48 to 60% of the sediment load at Kratie. Deposited sediment varies from 19 to 23% of the annual load at Kratie in Cambodian floodplains, and from 1 to 6% in the compartmented and diked floodplains in Vietnam. Annual deposited nutrients (N, P, K), which are associated with the sediment deposition, provide on average more than 50% of mineral fertilizers typically applied for rice crops in non-flooded ring dike floodplains in Vietnam. Through the quantification of sediment and related nutrient input, the presented study provides a quantitative basis for estimating the benefits of annual Mekong floods for agriculture and fishery, and is an important piece of information with regard to the assessment of the impacts of deltaic subsidence and climate-change-related sea level rise on delta morphology.

scholarly journals 3 Dimensional Modeling of Advection-Diffusion Equation

2019 ◽  
Author(s):  
Amin Ilia
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Transport Model ◽  
Three Dimensional ◽  
Water Levels ◽  
Dynamics Simulation ◽  
Advection Diffusion ◽  
Sediment Transport Model ◽  
Time Splitting ◽  
2D Model

Estimation of flows and sediment transport is challenging as many complexes and interacting physical phenomena need to be accounted for. In this research, a coupled two-dimensional finite volume flow model and a three-dimensional sediment transport model were developed in Fortran. In this model, the depth-integrated current vectors and water level were computed by 2D shallow water equations as the 2D model is computationally much faster than the 3D model. The depth-integrated current vectors were distributed in depths using a logarithmic current distribution equation, log of the wall. These distributed velocities and simulated water levels were used for three-dimensional sediment transport model which is generated using the same scheme. A 3D sediment transport model was preferred over a 2D model as 3D sediment model can estimate vertically diffusion of sediment mass from bedload to suspended sediment load which significantly improves the prediction of morphology evolutions.In order to discretize each subset of equations with the best-suited method, I utilized a time-splitting technique. As a result, I applied the second-order Fromm scheme which was found the best method for solving advection terms and semi-implicit forward time central space method which was found the best method for solving diffusion terms. The time-splitting scheme also reduced the complicity, therefore, the solution became simple and attractive to apply. For developing the sediment transport model, I applied this advection-diffusion concept to estimate the distribution of suspended sediment concentration and the Van Rijn (1981) scheme for the estimation of bedload sediment transport. As it’s very important to estimate and predict this phenomenon accurately, I compared the model with a lab trench experiment and the model results were in agreement with lab experiments. It was shown that the model could accurately simulate sedimentation on the downsloping (deceleration) section and erosion on the upsloping (acceleration) section of a marine trench. This would cause lateral movement of the channel toward the current direction. Being capable of accurate sediment transport and morphological dynamics simulation in this complex setting, this model is validated to be applied to other marine problems.

scholarly journals A Three-Dimensional Flow and Sediment Transport Model for Free-Surface Open Channel Flows on Unstructured Flexible Meshes

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 18 ◽  
Author(s):  
Yong Lai ◽  
Kuowei Wu
Keyword(s):  
Free Surface ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Open Channel ◽  
Transport Model ◽  
Three Dimensional ◽  
Suspended Sediment Transport ◽  
Open Channel Flows ◽  
Sediment Transport Model ◽  
Flow And Sediment Transport

Three-dimensional (3D) hydrostatic-pressure-assumption numerical models are widely used for environmental flows with free surfaces and phase interfaces. In this study, a new flow and sediment transport model is developed, aiming to be general and more flexible than existing models. A general set of governing equations are used for the flow and suspended sediment transport, an improved solution algorithm is proposed, and a new mesh type is developed based on the unstructured polygonal mesh in the horizontal plane and a terrain-following sigma mesh in the vertical direction. The new flow model is verified first with the experimental cases, to ensure the validity of flow and free surface predictions. The model is then validated with cases having the suspended sediment transport. In particular, turbidity current flows are simulated to examine how the model predicts the interface between the fluid and sediments. The predicted results agree well with the available experimental data for all test cases. The model is generally applicable to all open-channel flows, such as rivers and reservoirs, with both flow and suspended sediment transport issues.

scholarly journals Contributions of catchment and in-stream processes to suspended sediment transport in a dominantly groundwater-fed catchment

2018 ◽  
Vol 22 (7) ◽  
pp. 3903-3921 ◽  
Author(s):  
Yan Liu ◽  
Christiane Zarfl ◽  
Nandita B. Basu ◽  
Marc Schwientek ◽  
Olaf A. Cirpka
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Urban Areas ◽  
Transport Model ◽  
Bank Erosion ◽  
Main Stem ◽  
Shear Stresses ◽  
Sediment Transport Model ◽  
Bed Erosion ◽  
River Hydraulics

Abstract. Suspended sediments impact stream water quality by increasing the turbidity and acting as a vector for strongly sorbing pollutants. Understanding their sources is of great importance to developing appropriate river management strategies. In this study, we present an integrated sediment transport model composed of a catchment-scale hydrological model to predict river discharge, a river-hydraulics model to obtain shear stresses in the channel, a sediment-generating model, and a river sediment-transport model. We use this framework to investigate the sediment contributions from catchment and in-stream processes in the Ammer catchment close to Tübingen in southwestern Germany. The model is calibrated to stream flow and suspended-sediment concentrations. We use the monthly mean suspended-sediment load to analyze seasonal variations of different processes. The contributions of catchment and in-stream processes to the total loads are demonstrated by model simulations under different flow conditions. The evaluation of shear stresses by the river-hydraulics model allows the identification of hotspots and hot moments of bed erosion for the main stem of the Ammer River. The results suggest that the contributions of suspended-sediment loads from urban areas and in-stream processes are higher in the summer months, while deposition has small variations with a slight increase in summer months. The sediment input from agricultural land and urban areas as well as bed and bank erosion increase with an increase in flow rates. Bed and bank erosion are negligible when flow is smaller than the corresponding thresholds of 1.5 and 2.5 times the mean discharge, respectively. The bed-erosion rate is higher during the summer months and varies along the main stem. Over the simulated time period, net sediment trapping is observed in the Ammer River. The present work is the basis to study particle-facilitated transport of pollutants in the system, helping to understand the fate and transport of sediments and sediment-bound pollutants.

scholarly journals Numerical Study of Remote Sensed Dredging Impacts on the Suspended Sediment Transport in China’s Largest Freshwater Lake

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2449 ◽  
Author(s):  
Jianzhong Lu ◽  
Haijun Li ◽  
Xiaoling Chen ◽  
Dong Liang
Keyword(s):  
Remote Sensing ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Transport Model ◽  
Poyang Lake ◽  
Numerical Study ◽  
Point Sources ◽  
Freshwater Lake ◽  
Suspended Sediment Transport ◽  
Sediment Transport Model

As the largest freshwater lake in China, Poyang Lake plays an important role in the ecosystem of the Yangtze River watershed. The high suspended sediment concentration (SSC) has been an increasingly significant problem under the influence of extensive sand dredging. In this study, a hydrodynamic model integrated with the two-dimensional sediment transport model was built for Poyang Lake, considering sand dredging activities detected from satellite images. The sediment transport model was set with point sources of sand dredging, and fully calibrated and validated by observed hydrological data and remote sensing results. Simulations under different dredging intensities were implemented to investigate the impacts of the spatiotemporal variation of the SSC. The results indicated that areas significantly affected by sand dredging were located in the north of the lake and along the waterway, with a total affected area of about 730 km2, and this was one of the main factors causing high turbidity in the northern part of the lake. The SSC in the northern area increased, showing a spatial pattern in which the SSC varied from high to low from south to north along the main channel, which indicated close agreement with the results captured by remote sensing. In summary, this study quantified the influence of human induced activities on sediment transport for the lake aquatic ecosystem, which could help us to better understand the water quality and manage water resources.

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