scholarly journals Efectos de las extracciones de áridos sobre el transporte de sedimentos en suspensión en ríos de montaña (alto río Cinca, Pirineo Central)

2018 ◽  
Vol 44 (2) ◽  
pp. 641 ◽  
Author(s):  
M. Béjar ◽  
D. Vericat ◽  
I. Nogales ◽  
F. Gallart ◽  
R.J. Batalla
Keyword(s):  
Sediment Transport ◽  
Reference Conditions ◽  
Suspended Sediment Transport ◽  
Sediment Grain Size ◽  
Total Load ◽  
Fluvial Systems ◽  
Gravel Mining ◽  
Order Of Magnitude ◽  
The Impact ◽  
Reference Section

This paper examines the effects of gravel mining on the suspended sediment transport in the Upper River Cinca (Central Pyrenees). Discharge, sediment transport and sediment grain-size distribution were measured, sampled and further determined in five monitoring sections along a 5-km river reach. Samples were taken at a section upstream from the mined area (i.e. reference section) and in four sections downstream (0, 200, 500 and 1500 meters). The results show that sediment concentrations downstream from the target site were up to one order of magnitude higher than in the reference section. Average concentrations during the impact were similar to those observed during floods, with maximum values attaining 6 g/l. Total load ranged from 2.2 to 17 Mg/day between sections; these values include the effects of the earth-moving works performed before the mining started. Concentrations at the lowermost section of the study reach were similar to those observed at the upstream reference section, suggesting that most of the suspended material was deposited in the channel. The transported material was coarse than that sampled under reference conditions; nevertheless, largest particles settled quickly, suggesting a selective transport downstream. This study constitutes a first step towards a better understanding of local sediment dynamics in rivers affected by maintenance works and related activities, such as gravel mining, and, overall, supports the comprehensive assessment of the effects of human actions on channel morphodynamics and the ecological functioning of mountain fluvial systems.

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.

scholarly journals SEDIMENT TRANSPORT INVESTIGATIONS IN A NEW ZEALAND TIDAL INLET

1982 ◽  
Vol 1 (18) ◽  
pp. 147
Author(s):  
K.P. Black ◽  
T.R. Healy
Keyword(s):  
New Zealand ◽  
Sediment Transport ◽  
Skin Friction ◽  
Tidal Flow ◽  
Suspended Sediment Transport ◽  
Form Drag ◽  
Inlet System ◽  
Total Load ◽  
Friction Component ◽  
Load Transport

A study of sand and shell movement under the action of tidal flow was initiated in 1980 to ascertain the suitability of Whangarei Harbour at Marsden Point, New Zealand, for a proposed timber port. The aim was to assess the effects such a development may have on the sediment fluxes and the potential shoreline and channel instability that might be induced in the sandy inlet system. Vertical water velocity profiles were analysed to determine bed friction coefficients which were subsequently broken into two component parts: one due to form drag and the other associated with the skin friction. It was shown that the Vanoni and Hwang (1967) equation for form drag can be extrapolated to include drag under tidal flow over megaripples. The skin friction component was obtained from the speed at 1m above the bed and the De5 grain size, by utilising the Karman-Prandtl equation. This was applied to analysis of bedload trap yields and bedform advance rates over megaripples and good agreement with the Yalin bedload equation for plane beds was obtained. Suspended sediment transport was found to vary with U^7-75 and total load rates were in general agreement with the Engelund Hansen equation but deviations occurred due partly to expected form drag components being out of phase with the flow because of bedform hysteresis. Under tidal flow, the velocity at 1m was found to be a better predictor of sediment transport than the shear stress obtained from the velocity profile, thus methods presented in this paper use the lm speed for determination of total load transport.

scholarly journals Response of tidal flow regime and sediment transport in North Male' Atoll, Maldives to coastal modification and sea level rise

2020 ◽  
Author(s):  
Shuaib Rasheed ◽  
Simon C. Warder ◽  
Yves Plancherel ◽  
Matthew D. Piggott
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Sea Level Rise ◽  
Sea Level ◽  
Land Reclamation ◽  
Tidal Flow ◽  
Sediment Grain Size ◽  
Sediment Distribution ◽  
Time Periods ◽  
The Impact

Abstract. Changes to coastlines and bathymetry alter tidal dynamics and associated sediment transport process, impacting upon a number of threats facing coastal regions, including flood risk and erosion. Especially vulnerable are coral atolls such as those that make up the Maldives archipelago which has undergone significant land reclamation in recent years and decades, and is also particularly exposed to sea level rise. Here we develop a tidal model of Male' Atoll, Maldives, and use it to assess potential changes to sediment grain size distributions under sea level rise and coastline alteration scenarios. The results indicate that the impact of coastline modification over the last two decades at the island scale is not limited to the immediate vicinity of the modified island, but can also significantly impact the sediment grain size distribution across the wider atoll basin. Additionally, the degree of change in sediment distribution which can be associated with sea level rise that is projected to occur over relatively long time periods is predicted to occur over far shorter time periods with coastline changes, highlighting the need to better understand, predict and mitigate the impact of land reclamation and other coastal modifications before conducting such activities.

scholarly journals Appraising the Impact of Naraj Barrage on Sedimentation of Chilika Lagoon; the Soft Computing Model for Prediction

2020 ◽  
pp. 31-41
Author(s):  
Siba Prasad Mishra ◽  
Ananta Charan Ojha
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Learning Algorithm ◽  
River System ◽  
Suspended Sediment Transport ◽  
Chilika Lagoon ◽  
Surrounding Environment ◽  
Ensemble Machine Learning ◽  
The Impact ◽  
Total Sediment

Estimation of suspended sediment transport in a catchment area is very important to manage water resources, construction of dam and barrage, as well as to protect the surrounding environment. The daily monsoon sediment and flow were observed physically and quantity of total sediment input by the two major rivers of the south Mahanadi deltaic rivers to Lagoon Chilika were calculated during pre Naraj barrage (FY 2000 to 2003) and post Naraj Barrage period (FY’s 2004, 2012, 2013) establishing an observatory in the rivers the Daya and the Bhargovi.[b] The non-linear complex relationship between quantity of suspended sediment transport and volume of river-discharge inflicts challenge to the estimation process. In this paper, two southern-most distributaries, the Daya and the Bhargovi of the Mahanadi River System which flow into Chilika lagoon are studied. Random Forest, an ensemble machine learning algorithm is used to estimate the transport of sediment by these two distributaries using predictive modeling. Predicted figures based on the gathered data from these distributaries during pre-barrage period 2000-2003 have been compared with the observed data gathered in post-barrage years 2004, 2012 and 2013. Comparative data suggests that the construction of Naraj barrage has significantly reduced the concentration of sediment influx into Chilika lagoon while controlling the discharge through effective barrage management.

scholarly journals Modeling Hydro-Dynamics in a Harbor Area in the Daishan Island, China

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 192 ◽  
Author(s):  
Yuting Li ◽  
Zhiyao Song ◽  
Guoqiang Peng ◽  
Xuwen Fang ◽  
Ruijie Li ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Flow Velocity ◽  
Suspended Sediment ◽  
Hydrodynamic Model ◽  
Transport Model ◽  
Measurement Data ◽  
Cross Flow ◽  
Sediment Concentration ◽  
Suspended Sediment Transport ◽  
The Impact

This study presents an incorporation and application of a two-dimensional, unstructured-grid hydrodynamic model with a suspended sediment transport module in Daishan, China. The model is verified with field measurement data from 2017: water level, flow velocities and suspended sediment concentration (SSC). In the application on the Daishan, the performance of the hydrodynamic model has been satisfactorily validated against observed variations of available measurement stations. Coupled with the hydrodynamic model, a sediment transport model has been developed and tested. The simulations agreed quantitatively with the observations. The validated model was applied to the construction of breakwaters and docks under a different plan. The model can calculate the flow field and siltation situation under different breakwater settings. After we have analyzed the impact of existing breakwater layout schemes and sediment transport, a reasonable plan will be selected. The results show that the sea area near the north of Yanwo Shan and Dongken Shan has a large flow velocity exceeding 2.0 m/s and the flow velocity within the isobath of 5 m is small, within 0.6 m/s. According to the sediment calculation, the dock project is feasible. However, the designed width of the fairway should be increased to ensure the navigation safety of the ship according to variation characteristics of cross flow velocity in channel.

scholarly journals Response of tidal flow regime and sediment transport in North Malé Atoll, Maldives, to coastal modification and sea level rise

Ocean Science ◽  
2021 ◽  
Vol 17 (1) ◽  
pp. 319-334
Author(s):  
Shuaib Rasheed ◽  
Simon C. Warder ◽  
Yves Plancherel ◽  
Matthew D. Piggott
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Sea Level Rise ◽  
Sea Level ◽  
Land Reclamation ◽  
Transport Processes ◽  
Sediment Grain Size ◽  
Sediment Distribution ◽  
Time Periods ◽  
The Impact

Abstract. Changes to coastlines and bathymetry alter tidal dynamics and associated sediment transport processes, impacting upon a number of threats facing coastal regions, including flood risk and erosion. Especially vulnerable are coral atolls such as those that make up the Maldives archipelago, which has undergone significant land reclamation in recent years and decades and is also particularly exposed to sea level rise. Here we develop a tidal model of Malé Atoll, Maldives, the first atoll-scale and multi-atoll-scale high-resolution numerical model of the atolls of the Maldives and use it to assess potential changes to sediment grain size distributions in the deeper atoll basin, under sea level rise and coastline alteration scenarios. The results indicate that the impact of coastline modification over the last two decades at the island scale is not limited to the immediate vicinity of the modified island but can also significantly impact the sediment grain size distribution across the wider atoll basin. Additionally, the degree of change in sediment distribution which can be associated with sea level rise that is projected to occur over relatively long time periods is predicted to occur over far shorter time periods with coastline changes, highlighting the need to better understand, predict and mitigate the impact of land reclamation and other coastal modifications before conducting such activities.

scholarly journals How do modeling choices and erosion zone locations impact the representation of connectivity and the dynamics of suspended sediments in a multi-source soil erosion model?

2021 ◽  
Vol 9 (1) ◽  
pp. 123-144
Author(s):  
Magdalena Uber ◽  
Guillaume Nord ◽  
Cédric Legout ◽  
Luis Cea
Keyword(s):  
Sediment Transport ◽  
Soil Erosion ◽  
Suspended Sediment ◽  
Structural Connectivity ◽  
Sediment Flux ◽  
Suspended Sediment Transport ◽  
Sediment Sources ◽  
Flux Variability ◽  
Suspended Sediment Flux ◽  
The Impact

Abstract. Soil erosion and suspended sediment transport understanding is an important issue in terms of soil and water resources management in the critical zone. In mesoscale watersheds (>10 km2) the spatial distribution of potential sediment sources within the catchment associated with rainfall dynamics is considered to be the main factor in the observed suspended sediment flux variability within and between runoff events. Given the high spatial heterogeneity that can exist for such scales of interest, distributed physically based models of soil erosion and sediment transport are powerful tools to distinguish the specific effect of structural and functional connectivity on suspended sediment flux dynamics. As the spatial discretization of a model and its parameterization can crucially influence how the structural connectivity of the catchment is represented in the model, this study analyzed the impact of modeling choices in terms of the contributing drainage area (CDA) threshold to define the river network and of Manning's roughness parameter (n) on the sediment flux variability at the outlet of two geomorphologically distinct watersheds. While the modeled liquid and solid discharges were found to be sensitive to these choices, the patterns of the modeled source contributions remained relatively similar when the CDA threshold was restricted to the range of 15 to 50 ha, with n restricted to the range 0.4–0.8 on the hillslopes and to 0.025–0.075 in the river. The comparison of the two catchments showed that the actual location of sediment sources was more important than the choices made during discretization and parameterization of the model. Among the various structural connectivity indicators used to describe the geological sources, the mean distance to the stream was the most relevant proxy for the temporal characteristics of the modeled sedigraphs.

scholarly journals LABORATORY EXPERIMENT ON CROSS-SHORE BARRIER SPIT EVOLUTION BY STORM DYNAMICS

2011 ◽  
Vol 1 (32) ◽  
pp. 32
Author(s):  
Nguyen Xuan Tinh ◽  
Magnus Larson ◽  
Chantal Donnelly ◽  
Hitoshi Tanaka
Keyword(s):  
Sediment Transport ◽  
Laboratory Experiment ◽  
Water Level ◽  
Barrier Island ◽  
Order Of Magnitude ◽  
Storm Dynamics ◽  
Mean Water Level ◽  
The Impact ◽  
Further Development ◽  
High Possibility

Every year there are many severe storms occurring around the world, in general, and in Japan, in particular. The occurrence of storms is expected to increase because of the global warming effects. An increasing wave height together with a rising mean water level during a storm create a high possibility for waves to overtop the beach crest causing a lot of sediment to be eroded to offshore areas or deposited in the inland direction. The study of the barrier island response to storms has therefore become very important in terms of sediment transport and beach morphology change, as well as damage to nearshore structures due to runup overwash and inundation overwash. However, changes in the beach profile and prevailing sediment transport mechanisms during a real event are difficult to obtain. Thus, laboratory studies are necessary to conduct. This study presents a laboratory experiment on the impact of storms on a sandy barrier islands. The main aim is to investigate the entire barrier island (or sand spit) response due to storm conditions considering the increase in water level due to storm surge. Also, further development of an analytical model for barrier profile change caused by runup overwash is presented and obtained results overall captured order-of-magnitude barrier face retreat and volume changes after the storm.

scholarly journals Coastal Sediment Transport along Kalpakkam using Sediment Trend Exploaration and Numerical Modelling

2019 ◽  
Vol 8 (2S11) ◽  
pp. 3011-3015
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Trend Analysis ◽  
Coastal Sediment ◽  
Sediment Grain Size ◽  
Coastal Sediment Transport ◽  
The Impact ◽  
Grain Size Trend Analysis

The impact of coastal sediment transport in the nearshore region is significant and the need for improved sediment quantification techniques appears to be universally accepted. The coastal sediment transport models presently in use were derived empirically from very sparse measurements of waves and currents and from laboratory experiments. The shoreline of Kadalur fishing villages near Kalpakkam has been experiencing erosion due to occurrence of cyclones every monsoon. Palar River with its confluence in the Bay of Bengal at the northern tip of the Kadalur villages has its mouth closed due to negligible river flow. The purpose of this study is to assess sediment dynamics in the Kalpakkam coast using two independent approaches; namely Sediment Trend Analysis (STA) and two dimensional numerical modelling. The latter can track the movement of individual particles. Numerical modelling approach is based on Delft3D model which allows the coupling of flow and wave modules. STA and numerical modelling results can provide sediment transport direction. The combination of both approaches provides a means of verification of sedimentation processes. The basic assumption in STA is that sediment transport can be responsible for the differences in sediment grain size distributions. For Grain Size Trend Analysis, grab samples were collected throughout the nearshore area. Grain Size Trend Analysis was then carried out and subsequent results were plotted to obtain the sediment transport pattern for the region. The results obtained are compared with the numerical model results and also used for validation of sediment transport evaluated using the numerical model.

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