scholarly journals Suspended-Sediment Distribution Patterns in Tide-Dominated Estuaries on the Eastern Amazon Coast: Geomorphic Controls of Turbidity-Maxima Formation

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1568
Author(s):  
Vando J. C. Gomes ◽  
Nils E. Asp ◽  
Eduardo Siegle ◽  
José Diego Gomes ◽  
Ariane M. M. Silva ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Regional Climate ◽  
Strong Dependence ◽  
River Sediments ◽  
River Mouth ◽  
Sediment Supply ◽  
Amazon River ◽  
Sediment Delivery ◽  
Sediment Distribution ◽  
The World

In tide-dominated estuaries, maximum-turbidity zones (MTZs) are common and prominent features, characterized by a peak in suspended-sediment concentration (SSC) associated with estuarine processes. The Brazilian Amazon coast includes many estuaries, experiencing macrotidal conditions. MTZs are expected to occur and are crucial for sediment delivery to the longest continuous mangrove belt of the world. The area is under influence of the Amazon River plume (ARP), the main SSC source, as local rivers do not deliver substantial sediment supply. To assess the processes that allow the ARP to supply sediment to the estuaries and mangrove belt along the Amazon coast, the results from previous individual studies within five Amazon estuaries (Mocajuba, Taperaçu, Caeté, Urumajó and Gurupi) were compared with regards to SSC, salinity, morphology and tidal propagation. This comparison reinforces that these estuaries are subject to similar regional climate and tidal variations, but that their dynamics differ in terms of distance from the Amazon River mouth, importance of the local river sediment source, and morphology of the estuarine setting. The Urumajó, Caeté and Gurupi are hypersynchronous estuaries where perennial, classic MTZs are observed with SSC > 1 g·L−1. This type of estuary results in transport convergence and MTZ formation, which are suggested to be the main processes promoting mud accumulation in the Amazonian estuaries and therefore the main means of mud entrapment in the mangrove belt. The Mocajuba and the Taperaçu estuaries showed synchronous and hyposynchronous processes, respectively, and do not present classic MTZs. In these cases, the proximity to the ARP for the Mocajuba and highly connected tidal channels for the Taperaçu estuary, assure substantial mud supply into these estuaries. This study shows the strong dependence of the estuaries and mangrove belt on sediment supply from the ARP, helping to understand the fate of Amazon River sediments and providing insights into the mechanisms providing sediment to estuaries and mangroves around the world, especially under the influence of big rivers.

Sediment retention in river deltas and feedbacks with delta morphology

2021 ◽  
Author(s):  
Jaap Nienhuis ◽  
Juan Paniagua-Arroyave ◽  
Frances Dunn ◽  
Sagy Cohen ◽  
Torbjorn Tornqvist
Keyword(s):  
River Mouth ◽  
Sediment Traps ◽  
Sediment Supply ◽  
Sediment Retention ◽  
Sediment Delivery ◽  
Cross Sectional ◽  
Fluvial Sediment ◽  
River Deltas ◽  
Sediment Loads ◽  
The Mean

<p>Fluvial sediments have collectively formed about 900,000 km<sup>2</sup> of deltaic land since Holocene sea-level rise slowed down. The rate at which deltas have retained fluvial sediment to build deltaic land, however, has varied greatly between different deltas. Here we quantify sediment retention in the delta topset and foreset for 3,556 deltas globally. We estimate retention from data on delta morphology and cross-sectional area, combined with WBMSed data on fluvial suspended sediment supply. Deltas, on average, retain 25±2% (standard error of the mean) of the fluvial sediment in their topset and 31±2% in their foreset. Because topset sediment retention reduces the sediment delivery to the river mouth, it sets up a feedback with processes that build delta morphology. Waves reduce topset sediment retention whereas tides increase it. Tide dominated deltas retain 61±24% on their topset, on average, compared to 21±3% and 24±2% for river- and wave-dominated deltas, respectively. Larger deltas trap more sediment, but not in comparison to their larger sediment loads, making them relatively inefficient sediment traps.</p>

Continuous, diurnally fluctuating turbidity currents in Kluane Lake, Yukon Territory

2008 ◽  
Vol 45 (10) ◽  
pp. 1123-1138 ◽  
Author(s):  
Sarah Crookshanks ◽  
Robert Gilbert
Keyword(s):  
Suspended Sediment ◽  
River Mouth ◽  
Sediment Traps ◽  
Yukon Territory ◽  
Turbidity Currents ◽  
Paleoenvironmental Reconstruction ◽  
Sedimentary Processes ◽  
Sediment Distribution ◽  
Diurnal Range ◽  
Kluane Lake

Modern sedimentary processes were studied in Kluane Lake, Yukon Territory, to determine the spatial and temporal patterns of sediment distribution in a large, dynamic, glacier-fed lake. Data from a river monitoring station, moored instruments, sediment traps, and water-column profiles in the lake were used to document lacustrine sedimentary processes in 2006 and 2007. During the peak melt season, the suspended sediment concentration of Slims River is weakly dependent on river discharge and can reach up to 5 g L–1, although a diurnal range between 1 and 2 g L–1 is more commonly observed. The high suspended sediment load in the river generates continuous, diurnally fluctuating turbidity currents in Kluane Lake with maximum velocities up to 0.6 m s–1. During times of peak flow, variations in velocity can be traced to beyond 4 km from the river mouth. The vertical concentration profiles, mass accumulation rates, and suspended sediment loads show distinctive longitudinal variations; the highest rate of accumulation occurs ∼1 km from the point of inflow, which is concurrent with a distinct change in flow structure. Diurnal laminations are apparent in sediment traps close to the point of inflow and can be directly linked to variations in current velocity; however, these laminations do not occur consistently over space or time. These results suggest that long-term measurement records of lacustrine turbidity currents provide valuable insights regarding the multiple scales of environmental variability and have important implications for paleoenvironmental reconstruction using lacustrine sediments.

scholarly journals Impact of River Dams on Littoral Cells Located Adjacent to the River Mouth

2021 ◽  
Vol 16 (3) ◽  
pp. 942-952
Author(s):  
KAMAL NAG
Keyword(s):  
Image Processing ◽  
Suspended Sediment ◽  
River Mouth ◽  
Temporal Analysis ◽  
Sediment Budget ◽  
Sediment Supply ◽  
Water Diversion ◽  
Littoral Cells ◽  
Geomorphological Changes ◽  
The Impact

Terrestrial sediment is a major source of sediment to all coasts. Suspended sediment is carried away by the rivers and supplied to the coast to maintain sediment budget. The construction of dams across the rivers arrest sediment behind it and affect the sediment budget of littoral cells along the coast. Reduction in sediment supply induces ecological as well as geomorphological changes along the shoreline. Coastal erosion may accelerate due to reduced sediment influx. With the growing number of cross-river dams and water diversion projects, it has become a major concern before the scientific community to measure, understand and find solutions to multi-fold geo-environmental problems that are arising out of river damming. The present study aims to find out the impact of dams on the coast. It examines how the changes in the suspended sediment supply of an Indian river impact the coast in terms of loss of area due to erosion. Temporal analysis of geomorphological changes along the shoreline in relation to sediment influx holds immense importance to coastal management essential for the sustainable life and livelihood of coastal communities. Scientific investigation into the impact of river dams on the coastal environment is likely to provide a strong ground to reconsider the way present basin development projects function. Areal changes in littoral sediment cells adjacent to the river mouth have been quantified and correlated with changes in sediment influx. Changes along the shorelines have been detected through multispectral satellite images of Landsat belonging to different dates. Image processing and quantification of changes have been performed in QGIS 3.14 “Pi” platform. Virtual raster, raster calculator, field calculator and other required tools in QGIS were used during image processing.

scholarly journals Modern sedimentary processes along the Doce river adjacent continental shelf

2015 ◽  
Vol 45 (4) ◽  
pp. 635-644 ◽  
Author(s):  
Valéria da Silva Quaresma ◽  
Geórgia Catabriga ◽  
Silvia Nossa Bourguignon ◽  
Estefânia Godinho ◽  
Alex Cardoso Bastos
Keyword(s):  
Continental Shelf ◽  
River Mouth ◽  
High Energy ◽  
Sediment Supply ◽  
Major Influence ◽  
Carbonate Content ◽  
Sedimentary Processes ◽  
Sediment Distribution ◽  
Shelf Sediment ◽  
Doce River

In areas of the continental shelf where sediment supply is greater than the sediment dispersion capacity, an extensive terrigenous deposits and consequently submerged deltas can be formed. The Eastern Brazilian shelf is characterized by the occurrence of river feed deltas in between starving coasts. Herein, modern sedimentary processes acting along the Doce river adjacent continental shelf are investigated. The main objective was to understand the shelf sediment distribution, recognizing distinct sedimentary patterns and the major influence of river sediment discharge in the formation of shelf deposits. The study used 98 surficial samples that were analyzed for grain size, composition and bulk density. Results revealed 3 distinct sectors: south - dominated by mud fraction with a recent deposition from riverine input until 30 m deep and from this depth bioclastic sands dominate; central north - sand mud dominated, been recognized as a bypass zone of resuspended sediment during high energy events; and north - relict sands with high carbonate content. The modern sedimentation processes along the Doce river continental shelf is dominated by distinct sedimentary regimes, showing a strong fluvial influence associated with wave/wind induced sediment dispersion and a carbonate regime along the outer shelf. These regimes seem to be controlled by the distance from the river mouth and bathymetric gradients.

Suspended sediment distribution and residual transport in the coastal ocean off the Ganges-Brahmaputra river mouth

1994 ◽  
Vol 120 (1-2) ◽  
pp. 41-61 ◽  
Author(s):  
Dilip K. Barua ◽  
Steven A. Kuehl ◽  
Richard L. Miller ◽  
Williard S. Moore
Keyword(s):  
Suspended Sediment ◽  
River Mouth ◽  
Coastal Ocean ◽  
Brahmaputra River ◽  
Sediment Distribution ◽  
Residual Transport ◽  
The Ganges

The effect of climate change on sediment distribution and delivery within the Rhine-Meuse Delta

2020 ◽  
Author(s):  
Jana Cox ◽  
Frances Dunn ◽  
Jaap Nienhuis
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Suspended Sediment ◽  
Sea Level ◽  
Anthropogenic Activities ◽  
Sediment Flux ◽  
Change Scenario ◽  
Sediment Delivery ◽  
Sediment Distribution ◽  
Sediment Redistribution

<p>The morphological and hydrological equilibrium of many deltas worldwide is changing due to anthropogenic activities. A key example of such a delta is the Rhine-Meuse Delta (RMD) in the Netherlands. It is home to an important shipping and economic centre (Rotterdam) and thus has been strongly affected by anthropogenic activities. Changes include embanking, narrowing and deepening of channels, major dredging and sediment relocation, the building of ports and harbours, and dam building upstream. There is currently a net annual loss of sediment from the delta. Considering current and future sea level rise it is crucial that the RMD receives sufficient sediment or it risks drowning, increased flood risk, decreased ecological area and channel bed degradation.</p><p>Here, we estimate the future delivery of suspended sediment from upstream using BQART, and the volume and sediment flux from the sea using a 1D morphological model. We ignore bedload fluxes as they make up a small proportion of the annual supply. We use these estimates to investigate sediment redistribution between channels in the RMD based on suspended sediment-discharge relations. Projections for 2050 and 2100 are presented based on region-specific climate scenarios for discharge and sea level and incorporate projected future upstream reservoir construction. The sediment concentration in the branches is compared with discharge-area relations and current bed level trends to demonstrate potential sedimentation-erosion trends for individual branches.</p><p>Projections for the 21<sup>st</sup> century indicate that sediment delivery to the RMD from upstream is likely to decrease slightly, while sea level rise will cause tidally driven suspended sediment delivery to move further inland. It is estimated that the already negative sediment budget of the delta will be exacerbated by dredging, which removes all incoming sediment at the coastal boundary. The severity of sediment starvation depends on the climate change scenario. Our work indicates that certain channels will be at risk of erosion due to this sediment starvation, whilst other branches will experience net sedimentation. Sediment input from the coast could also reach further inland, assuming current dredging practice remain unaltered, which could provide an opportunity for the system to regain equilibrium. We recommend that a sustainable sediment management strategy is undertaken in the region to counteract the negative effects of sediment starvation.  </p>

THE INITIAL RESULTS OF THE SUSPENDED SEDIMENT DYNAMICS DURING THE DRY SEASON IN THE HAU RIVER MOUTH AREA

2017 ◽  
Vol 17 (2) ◽  
Author(s):  
Nguyen Ngoc Tien ◽  
Dinh Van Uu ◽  
Nguyen Tho Sao ◽  
Do Huy Cuong ◽  
Nguyen Trung Thanh ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
River Mouth ◽  
Dry Season ◽  
Sediment Dynamics ◽  
Mouth Area ◽  
River Mouth Area ◽  
Initial Results
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