scholarly journals Sediment transport at the network scale and its link to channel morphology in the braided Vjosa River system

2021 ◽  
Author(s):  
Simone Bizzi ◽  
Marco Tangi ◽  
Rafael J. P. Schmitt ◽  
John Pitlick ◽  
Hervé Piégay ◽  
...  
Keyword(s):  
Sediment Transport ◽  
River System ◽  
Channel Morphology ◽  
Network Scale

scholarly journals A reduced-complexity model for sediment transport and step-pool morphology

2016 ◽  
Author(s):  
Matteo Saletti ◽  
Peter Molnar ◽  
Marwan A. Hassan ◽  
Paolo Burlando
Keyword(s):  
Sediment Transport ◽  
Channel Morphology ◽  
Sediment Supply ◽  
Physically Based ◽  
Load Transport ◽  
Physically Based Models ◽  
Bed Load Transport ◽  
Transport Particle ◽  
Reduced Complexity ◽  
Complex Phenomena

Abstract. A new particle-based reduced-complexity model, CAST, to simulate sediment transport and channel morphology in steep streams is presented. CAST contains phenomenological parameterizations, deterministic or stochastic, of sediment supply, bed load transport, particle entrainment and deposition in a cellular-automaton space with uniform grain size. The model can reproduce a realistic bed morphology and typical fluctuations in transport rates observed in steep channels. Particle hop distances, from entrainment to deposition, are well-fitted by exponential distributions, in agreement with field data. The effect of stochasticity both in the entrainment and in the input rate is shown. A stochastic parameterization of the entrainment is essential to create and maintain a realistic channel morphology, while sediment transport in CAST shreds the input signal and its stochastic variability. A jamming routine has been added to CAST to simulate the grain-grain and grain-bed interactions that lead to particle jamming and step formation in a step-pool stream. The results show that jamming is effective in generating steps in unsteady conditions. Steps are created during high- flow periods and they survive during low flows only in sediment- starved conditions, in agreement with the jammed-state hypothesis of Church and Zimmermann (2007). Reduced-complexity models such as CAST can give new insight into the dynamics of complex phenomena (such as sediment transport and bedform stability) and be useful to test research hypotheses, being an effective complement to fully physically-based models.

scholarly journals Variation in turbidity with precipitation and flow in a regulated river system – River Göta Älv, SW Sweden

2013 ◽  
Vol 10 (1) ◽  
pp. 255-293
Author(s):  
G. Göransson ◽  
M. Larson ◽  
D. Bendz
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Fresh Water ◽  
Surface Runoff ◽  
River System ◽  
Regulated River ◽  
Suspended Sediment Transport ◽  
Simple Relationship ◽  
Main River ◽  
Lake Vänern

Abstract. The turbidity variation in time and space is investigated in the downstream stretch of the river Göta Älv in Sweden. The river is heavily regulated and carries the discharge from the largest fresh water lake in Sweden, lake Vänern, to the outflow point in Göteborg Harbour on the Swedish west coast. The river is an important waterway and serves as fresh-water supply for 700 000 users. Turbidity is utilised as an indicator to ensure sufficient quality of the intake water to the treatment plant. The overall objective of the study was to investigate the influence of rainfall, surface runoff, and river water flow on the temporal and spatial variability of the turbidity in the regulated river system by employing statistical analysis of an extensive data set. Six-year long time series of daily mean values on precipitation, discharge, and turbidity from six stations along the river were examined primarily through linear correlation and regression analysis, combined with nonparametric tests and analysis of variance. The analyses were performed on annual, monthly, and daily basis, establishing temporal patterns and dependences, including seasonal changes, impacts from extreme events, influences from tributaries, and the spatial variation along the river. The results showed that there is no simple relationship between discharge, precipitation, and turbidity, mainly due to the complexity of the runoff process, the regulation of the river, and the effects of lake Vänern and its large catchment area. For the river Göta Älv, significant, positive correlations between turbidity, discharge, and precipitation could only be found during periods with high flow combined with heavy rainfall. Local precipitation does not seem to have any significant impact on the discharge in the main river, which is primarily governed by the precipitation at catchment scale. The discharge from the lake Vänern determines the base level for the turbidity in the river, whereas local surface runoff and tributary discharge induced by rainfall govern the temporal variability in turbidity. Autocorrelation analysis indicates a temporal persistence in turbidity of about 10 days. The results also show that erosion in the main river, from the river bed and banks, is not a dominant contributor to the suspended sediment transport in the river. Further studies on the correlation between turbidity and suspended sediment transport and in relation to erosion processes are suggested.

SEDIMENT TRANSPORT AND CHANNEL MORPHOLOGY OF SMALL, FORESTED STREAMS

2005 ◽  
Vol 41 (4) ◽  
pp. 853-876 ◽  
Author(s):  
Marwan A. Hassan ◽  
Michael Church ◽  
Thomas E. Lisle ◽  
Francesco Brardinoni ◽  
Lee Benda ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Channel Morphology

scholarly journals A reduced-complexity model for sediment transport and step-pool morphology

2016 ◽  
Vol 4 (3) ◽  
pp. 549-566 ◽  
Author(s):  
Matteo Saletti ◽  
Peter Molnar ◽  
Marwan A. Hassan ◽  
Paolo Burlando
Keyword(s):  
Sediment Transport ◽  
Cellular Automaton ◽  
Channel Morphology ◽  
Sediment Supply ◽  
Physically Based ◽  
Load Transport ◽  
Physically Based Models ◽  
Bed Load Transport ◽  
Reduced Complexity ◽  
Complex Phenomena

Abstract. A new particle-based reduced-complexity model to simulate sediment transport and channel morphology in steep streams in presented. The model CAST (Cellular Automaton Sediment Transport) contains phenomenological parameterizations, deterministic or stochastic, of sediment supply, bed load transport, and particle entrainment and deposition in a cellular-automaton space with uniform grain size. The model reproduces a realistic bed morphology and typical fluctuations in transport rates observed in steep channels. Particle hop distances, from entrainment to deposition, are well fitted by exponential distributions, in agreement with field data. The effect of stochasticity in both the entrainment and the input rate is shown. A stochastic parameterization of the entrainment is essential to create and maintain a realistic channel morphology, while the intermittent transport of grains in CAST shreds the input signal and its stochastic variability. A jamming routine has been added to CAST to simulate the grain–grain and grain–bed interactions that lead to particle jamming and step formation in a step-pool stream. The results show that jamming is effective in generating steps in unsteady conditions. Steps are created during high-flow periods and they survive during low flows only in sediment-starved conditions, in agreement with the jammed-state hypothesis of Church and Zimmermann (2007). Reduced-complexity models like CAST give new insights into the dynamics of complex phenomena such as sediment transport and bedform stability and are a useful complement to fully physically based models to test research hypotheses.

scholarly journals Channel morphology and prediction of mid-line channel migration in the reach of Ganga River using GIS and ARIMA modeling during 1975–2020

2021 ◽  
Author(s):  
Rajnish Kumar Verma ◽  
Kumar Ashwini ◽  
Ajai Singh
Keyword(s):  
Cross Sections ◽  
Arima Model ◽  
River System ◽  
Channel Length ◽  
Channel Morphology ◽  
Multi Temporal ◽  
River Training ◽  
The Mean ◽  
Predicted Values ◽  
Landsat Satellite

Abstract The dynamic nature of meandering poses several challenges in a river. The river Ganga shows severe bank erosion in many of its stretches which creates insecurity to the habitats. In the present study, channel morphology and lateral mid-line migration for 1975 to 2020 in 5 years intervals have been studied. The prediction of lateral mid-line migration from 2020 to 2050 by using multi-temporal Landsat satellite images was made by using the ARIMA model. The river reach was divided into 8 bends and 48 cross-sections were identified. The channel length was observed as 224.35 km in 1975 which reduces to 199.96 km in 2020. A decreasing trend was observed for the mean of channel length and meander ratio, and an increasing trend was noted in the mean of sinuosity ratio and tortuosity ratio. A total of 11 cross-sections showed the rightward shifting and 36 cross-sections showed the leftward shifting. Observed and predicted values showed a good R2 value of 0.90 and 0.89 at CS-24 and CS-25, respectively. The results may be used for planning and management of various river training work and understanding the river system dynamics.

scholarly journals River Sediment Transport Modeling of Ele River using Computational Fluid Dynamics Model of COMSOL Multiphysics Program

2021 ◽  
Vol 16 ◽  
pp. 1-7
Author(s):  
Joseph Ikenna Ubah ◽  
Louis Chukwuemeka Orakwe ◽  
Nelson Mbanefo Okoye ◽  
Kingsely Nnaemeka Ogbu
Keyword(s):  
Sediment Transport ◽  
Crop Production ◽  
Research Work ◽  
River System ◽  
Sediment Deposition ◽  
Low Flow ◽  
Coefficient Of Determination ◽  
Comsol Multiphysics ◽  
Particle Tracing ◽  
Study Results

Excessive sediment deposition results to hydro-ecological problems particularly for shallow streams that experience significant point-source pollution. In recent times, models have been employed to investigate sediment transport in river systems. The aim of this research work is to model sediment transport of Ele River using particle tracing methodology. The governing equations of fluid flow and particle movement were modelled using COMSOL Multiphysics 5.3a. The result was validated using experimental data and the model result showed good agreement with coefficient of determination of 0.99. Study results showed that sediment at the river banks posses lower velocities compared to sediments in midstream. This implies higher sediment deposition at the banks due to low flow velocity. These sediments deposition constitute problems to the river system through degradation of water quality and blocking irrigation nozzles, impacting irrigation efficiency and crop production.

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