scholarly journals The impact of storms and stratification on sediment transport in the Rhine region of freshwater influence

2017 ◽  
Vol 122 (5) ◽  
pp. 4456-4477 ◽  
Author(s):  
Raúl P. Flores ◽  
Sabine Rijnsburger ◽  
Alexander R. Horner-Devine ◽  
Alejandro J. Souza ◽  
Julie D. Pietrzak
Keyword(s):  
Sediment Transport ◽  
Freshwater Influence ◽  
The Impact

Analyzing the impact of wooden debris on scour and sediment transport

2020 ◽  
pp. 743-750
Author(s):  
T. Johannsen ◽  
M. Weber ◽  
N. Saenger
Keyword(s):  
Sediment Transport ◽  
The Impact

scholarly journals Numerical modelling of sediment transport in the Adriatic Sea

2014 ◽  
Vol 11 (3) ◽  
pp. 1391-1433 ◽  
Author(s):  
A. Guarnieri ◽  
A. J. Souza ◽  
N. Pinardi ◽  
P. Traykovski
Keyword(s):  
Sediment Transport ◽  
Adriatic Sea ◽  
Transport Model ◽  
Data Availability ◽  
Western Coast ◽  
Po River ◽  
Northern Adriatic ◽  
Coastal Belt ◽  
Italian Coasts ◽  
The Impact

Abstract. A new sediment transport model, considering currents, tides and waves is presented for the Adriatic Sea basin. The simulations concentrate on the winter of 2002–2003 because of field data availability and interesting intermittent processes occurrence. A process oriented analysis is performed to investigate the impact that Sirocco and Bora wind regimes have on sediment transport. The comparisons of the simulations with the observed data show that the model is capable to capture the main dynamics of sediment transport along the Italian coasts and the sediment concentration within the water column. This latter can reach values up to several g L−1, especially within the first centimetres above the bottom. The sediments are transported mainly southwards along the Italian coasts, consistently with the known literature results, except during Sirocco wind events, which can be responsible for reversing the coastal circulation in the northern area of the basin, and consequently the sediment transport. The resuspension of sediments is also related to the specific wave regimes induced by Bora and Sirocco, the former inducing resuspension events near the coasts while the latter causing a more diffused resuspension regime in the Northern Adriatic basin. Beside the realistic representation of short timescales resuspension/deposition events due to storms, the model was also used to investigate persistent erosion or deposition areas in the Adriatic Sea. Two main depocenters were identified: one, very pronounced, in the surroundings of the Po river delta, and another one a few kilometres off the coast in front of the Ancona promontory. A third region of accumulation, even if less intense, was found to be offshore the southernmost limit of the Gargano region. On the contrary the whole western coast within a distance of a few kilometres from the shore was found to be subject to prevailing erosion. The comparison with observed accumulation and erosion data shows that the model captures well the main depocenters in the domain and the erosion within the very coastal belt of the western side of the basin, but seems to be too erosive in a few areas, in particular those where the contribution of sediment inflow to the sea of some minor but intermittently important rivers is not considered in a realistic way as input to the model.

scholarly journals Effects of Cascade Reservoir Systems on the Longitudinal Distribution of Sediment Characteristics: A Case Study of the Heihe River Basin

2021 ◽  
Author(s):  
Yu Wang ◽  
Bao-long Li ◽  
Juan-juan Liu ◽  
Qi Feng ◽  
Wei Liu ◽  
...  
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Longitudinal Distribution ◽  
Heihe River ◽  
Hydrodynamic Conditions ◽  
Sediment Grain Size ◽  
Cascade Reservoirs ◽  
Grain Size Distributions ◽  
Transport Patterns ◽  
The Impact

Abstract Spatial variations in grain-size parameters can reflect river sediment transport patterns and depositional dynamics. Therefore, 22 surficial sediment samples taken from the Heihe River and its cascade reservoirs were analyzed to better understand the impact of cascade reservoir construction on sediment transport patterns in inland rivers in China. The results showed that the longitudinal distribution of sediment grain size in the Heihe River was significantly affected by the influence of the cascade reservoirs. The grain size of the reservoir sediments within the cascade reservoir system was much lower than that of sediments in the natural river section, and the sediments in the natural river were well sorted, exhibiting leptokurtosis and positive or very positive skew. The lower reaches of the dammed river experienced strong erosion, and the grains of the bed sediments were coarse and poorly sorted; the grain-size distributions were more positively skewed and exhibited leptokurtosis. The backwater zone of the reservoir was influenced by both backwater and released water, and the sediment grain size was between the grain size of the natural river and that of the lower reaches of the dam; these sediments were moderately well sorted and had a positively skewed, leptokurtic grain-size distribution. Sedimentary environmental analysis revealed that the characteristics of the sediment grain size in an upstream tributary of the Heihe River were more influenced by source material than by hydrodynamic conditions, while the grain-size characteristics of the mainstream sediments were controlled mainly by hydrodynamic conditions.

3D numerical studies on stratification and mixing processes affecting fine sediment transport in the pre-dam of the Dhünn reservoir in Germany

2020 ◽  
Author(s):  
Wendy Gonzalez ◽  
Irina Klassen ◽  
Anne Jakobs ◽  
Frank Seidel
Keyword(s):  
Sediment Transport ◽  
Input Data ◽  
Measurement Data ◽  
Fine Sediment ◽  
Transport Processes ◽  
Transport Modeling ◽  
Wind Effects ◽  
Sediment Distribution ◽  
Vertical Diffusivity ◽  
The Impact

<p>Fine sediment transport processes and the thermodynamics in reservoirs are key processes governing the water quality of reservoirs. With regard to a sustainable sediment management of reservoirs, the prediction of sediment transport and deposition is becoming increasingly important.</p><p>The subject of the present work was the 3D numerical simulation of fine sediment transport in a reservoir taking into account stratification and mixing effects which in turn are caused by temperature gradients and wind effects. In order to understand and investigate the driving factors for stratification processes and their impact on fine sediment distribution, the great pre-dam of the Dhünn reservoir in Germany served as case study. The investigations were conducted in sensitivity analyses adopting a 3D sediment transport model with Delft 3D. The impact of various physical and numerical parameters on temperature and fine sediment transport modeling was examined: the number of vertical layers, the input data for the heat model (e.g. relative humidity, air temperature, cloud coverage, solar radiation), the vertical diffusivity and wind effects. The sensitivity studies showed that the input data for the heat model have a minor impact on the temperature and sediment transport modeling within the tested range of parameters. However, the vertical diffusivity and especially the inclusion of wind showed a greater influence on the simulated temperature and suspended sediment concentration gradients. The temperature modeling results by inclusion/exclusion of wind were qualitatively compared with temperature data from literature and with measurement data over a period of one month. Hereby, the simulations showed a good agreement with measurement data by exclusion of wind effects.</p><p>The results of the studies provide a solid basis for the development of further models in fields where fine sediment transport is affected by stratification processes and can also be very useful in terms of a better understanding of the interactions between temperature, wind and fine sediment transport.</p>

scholarly journals Flow dynamics and bedload sediment transport around paired deflectors for fish habitat enhancement: a field study in the Nicolet River

2007 ◽  
Vol 34 (6) ◽  
pp. 761-769 ◽  
Author(s):  
David M Carré ◽  
Pascale M Biron ◽  
Susan J Gaskin
Keyword(s):  
Sediment Transport ◽  
Radio Frequency Identification ◽  
Fish Habitat ◽  
Sediment Traps ◽  
Bedload Transport ◽  
Flow Dynamics ◽  
Left Bank ◽  
Passive Integrated Transponder ◽  
Bedload Sediment ◽  
The Impact

Schemes to restore fish habitat in rivers often involve installing instream structures such as current deflectors to create and maintain riffle-pool sequences. However, there is a lack of field studies on the impact of these structures on flow dynamics and bed topography. The objective of this research is to characterize flow dynamics and sediment transport around paired deflectors used to enhance fish habitat in the Nicolet River, Quebec. Bed and bank topography surveys were taken with a total station, and velocity and bed shear stress estimates were obtained from an acoustic doppler velocimeter. Bedload sediment transport was assessed by two methods: tracer rocks (painted "particles" and passive integrated transponder tags) and sediment traps. Results show marked differences in bedload sediment transport patterns between the left bank and the right bank downstream of the deflectors. This is surprising considering that paired deflectors should produce a relatively symmetrical disruption to the flow field on each side. More high-flow dynamics data during overtopping conditions are required to understand the complex interactions between these instream structures and bedload transport. Key words: stream restoration, pool, bedload transport, radio frequency identification (RFID), passive integrated transponder (PIT) tags, fieldwork, deflectors, fish habitat.

scholarly journals Runoff and Sediment Response to Cascade Hydropower Exploitation in the Middle and Lower Han River, China

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Junhong Zhang ◽  
Mingkun Sun ◽  
Zhimin Deng ◽  
Jing Lu ◽  
Dangwei Wang ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Sediment Load ◽  
Rapid Development ◽  
Strong Positive Correlation ◽  
Han River ◽  
Runoff Variation ◽  
Impact Index ◽  
Before And After ◽  
Time Periods ◽  
The Impact

With the rapid development of hydropower exploitation in China, changes in runoff and sediment transport have become a significant issue that cannot be neglected. In this study, the Han River was selected as a study case, where the runoff variation and changes in sediment load at the Baihe, Huangjiagang, Huangzhuang, and Xiantao stations were analyzed in different time periods. The results indicate that impact of cascade hydropower exploitation on runoff and sediment transport is significantly different even during the same time periods. After reservoir regulation, the decreasing of sediment load is faster than that of runoff. Strong positive correlation between runoff and sediment load exists during different time periods, while reservoir operation leads to different turning points at the Baihe, Huangjiagang, Huangzhuang, and Xiantao stations in the middle and lower Han River. As a key driving factor, runoff variation contributed to sediment transport with different impact indexCR. The impact indexCRbefore and after the first change point at the Baihe, Huangjiagang, Huangzhuang, and Xiantao stations is 43.35%, −3.68%, 11.17%, and 30.12%, respectively. This study helps us understand and evaluate the hydrological changes under cascade hydropower exploitation in the middle and lower Han River.

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