scholarly journals Numerical analysis of the influence of sea level rise on sediment deposition in the Yangtze Estuary channels

2015 ◽  
Author(s):  
R.Y. Shen ◽  
J. Gu ◽  
D. Wang ◽  
X.J. Zhang
Keyword(s):  
Numerical Analysis ◽  
Sea Level Rise ◽  
Sea Level ◽  
Yangtze Estuary ◽  
Sediment Deposition ◽  
The Yangtze Estuary

Sensitivity of tides and net water transport in an estuarine network to river discharge, network geometry and sea level rise

2020 ◽  
Author(s):  
Jinyang Wang ◽  
Huib de Swart
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Water Transport ◽  
River Discharge ◽  
Yangtze Estuary ◽  
Dry Season ◽  
Sea Level Changes ◽  
Wet Season ◽  
The Yangtze Estuary ◽  
And Sea Level

<div> <div> <div> <p>Quite a number of estuaries are characterised by a complex network of branching channels, in which the water motion is primarily driven by tides and river discharge. Examples are the Berau estuary (Indonesia), the Pearl estuary (China) and the Yangtze estuary (China). Knowledge about tides are required for construction of dikes/harbours, while knowledge about net water transport is important for agriculture, fresh water supply to cities and for quantifying transport of sediment, nutrients and etc.</p> <p>In this contribution, we present a generic, weakly nonlinear 2DV estuarine network model to study tides and net water transport and to understand the dependence of their along-channel and vertical structure on geometric characteristics and sea level changes. The model will be applied to the Yangtze Estuary for different situations, such as the wet and dry season, with and without a shortcut channel and sea level rise for scenarios for the coming 50 to 100 years.</p> <p>It will be demonstrated that, for the current conditions, the model results are in good agreement with observations. Both tidal amplitude and current are weaker during the wet season than that during the dry season and the reason for these changes will be explained in terms of river-tide interactions. Effects of local changes in geometry are investigated by creation of a shortcut channel between two main channels. Results show that changes in tides are merely local, but they can be rather strong. Sea level rise (up to 2 meters) causes tides to increase, mainly as a consequence of less friction resulting from larger water depth. Net water transport turns out to be less sensitive to geometry and sea level rise compared to tides.</p> </div> </div> </div>

Tidal level response to sea-level rise in the yangtze estuary

2012 ◽  
Vol 26 (1) ◽  
pp. 109-122 ◽  
Author(s):  
Zheng Gong ◽  
Chang-kuan Zhang ◽  
Li-ming Wan ◽  
Jun-cheng Zuo
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Yangtze Estuary ◽  
Tidal Level ◽  
The Yangtze Estuary

Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level rise

2021 ◽  
Author(s):  
Frances E. Dunn ◽  
Philip S. J. Minderhoud
Keyword(s):  
Land Use ◽  
Sea Level Rise ◽  
Sea Level ◽  
Mekong Delta ◽  
Sediment Deposition ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Relative Sea Level ◽  
Fluvial Sediment ◽  
Relative Sea Level Rise

<p>As one of the largest deltas in the world, the Mekong delta is home to over 17 million people and supports internationally important agriculture. Recently deposited sediment compacts and causes subsidence in deltas, so they require regular sediment input to maintain elevation relative to sea level. These processes are complicated by human activities, which prevent sediment deposition indirectly through reducing fluvial sediment supply and directly through the construction of flood defence infrastructure on deltas, impeding floods which deliver sediment to the land. Additionally, anthropogenic activities increase the rate of subsidence through the extraction of groundwater and other land-use practices.</p><p>This research shows the potential for fluvial sediment delivery to compensate for sea-level rise and subsidence in the Mekong delta over the 21st century. We use detailed elevation data and subsidence scenarios in combination with regional sea-level rise and fluvial sediment flux projections to quantify the potential for maintaining elevation relative to sea level in the Mekong delta. We present four examples of localised sedimentation scenarios in specific areas, for which we quantified the potential effectiveness of fluvial sediment deposition for offsetting relative sea-level rise. The presented sediment-based adaptation strategies are complicated by existing land use, therefore a change in water and sediment management is required to effectively use natural resources and employ these adaptation methods. The presented approach could be an exemplar to assess sedimentation strategy feasibility in other delta systems worldwide that are under threat from sea-level rise.</p>

scholarly journals Establishing a sediment budget in the newly created “Kleine Noordwaard” wetland area in the Rhine–Meuse delta

2018 ◽  
Vol 6 (1) ◽  
pp. 187-201 ◽  
Author(s):  
Eveline Christien van der Deijl ◽  
Marcel van der Perk ◽  
Hans Middelkoop
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Budget ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Created Wetlands ◽  
Intertidal Area ◽  
Soil Subsidence ◽  
Elevation Data ◽  
Marsh Erosion

Abstract. Many deltas are threatened by accelerated soil subsidence, sea-level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of sediment deposition, erosion, and their controls. Sediment dynamics has been studied at floodplains and marshes, but little is known about the sediment dynamics and budget of newly created wetlands. Here we take advantage of a recently opened tidal freshwater system to study both the mechanisms and controls of sediment deposition and erosion in newly created wetlands. We quantified both the magnitude and spatial patterns of sedimentation and erosion in a former polder area in which water and sediment have been reintroduced since 2008. Based on terrestrial and bathymetric elevation data, supplemented with field observations of the location and height of cut banks and the thickness of the newly deposited layer of sediment, we determined the sediment budget of the study area for the period 2008–2015. Deposition primarily took place in channels in the central part of the former polder area, whereas channels near the inlet and outlet of the area experienced considerable erosion. In the intertidal area, sand deposition especially takes place at low-lying locations close to the channels. Mud deposition typically occurs further away from the channels, but sediment is in general uniformly distributed over the intertidal area, due to the presence of topographic irregularities and micro-topographic flow paths. Marsh erosion does not significantly contribute to the total sediment budget, because wind wave formation is limited by the length of the fetch. Consecutive measurements of channel bathymetry show a decrease in erosion and deposition rates over time, but the overall results of this study indicate that the area functions as a sediment trap. The total contemporary sediment budget of the study area amounts to 35.7×103 m3 year−1, which corresponds to a net area-averaged deposition rate of 6.1 mm year−1. This is enough to compensate for the actual rates of sea-level rise and soil subsidence in the Netherlands.

Effect of decreasing sediment supply and sea level rise on the long-term morphodynamics of a large estuary

2021 ◽  
Author(s):  
Bing Yuan ◽  
Jian Sun ◽  
Binliang Lin ◽  
Fanyi Zhang
Keyword(s):  
Equilibrium State ◽  
Sea Level Rise ◽  
Sea Level ◽  
Yangtze Estuary ◽  
Sediment Supply ◽  
Bed Erosion ◽  
Adjustment Time ◽  
Riverine Sediment ◽  
And Sea Level

<p>Globally the riverine sediment supply to estuaries is decreasing and the mean sea level is rising, while the effects of these changes on the long-term estuarine morphodynamics have not been fully investigated. An idealized numerical model was used to explore the long-term morphodynamics of a large estuary subject to these changes. In the model, a funnel-shaped channel with fixed banks, constant riverine water and sediment fluxes, a single grain size and a semi-diurnal tide were used. A range of values of changes in the sediment supply (50-90% reduction) and sea level (1-5~mm/yr increase) were considered. Starting from an equilibrium state for an initial sediment supply, the estuary shifts to a new equilibrium for the considered changes on a timescale of millennia. Half of the bed level change occurs within several hundreds of years. A larger decrease in the sediment supply leads to a stronger bed erosion, while the corresponding adjustment time has minor changes in its range for the considered settings. When combined with sea level rise, the erosion is weakened and the adjustment time is shortened. The equilibrium state under sea level rise is characterized by a bed level keeping pace with the sea level and a significant amount of sediment being trapped in the estuary. Additional numerical experiments that use more realistic geometry and forcing of the Yangtze Estuary show that overall erosion of the estuary is expected for centuries.</p>

scholarly journals Effects of a large-scale, natural sediment deposition event on plant cover in a Massachusetts salt marsh

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245564
Author(s):  
G. E. Moore ◽  
D. M. Burdick ◽  
M. R. Routhier ◽  
A. B. Novak ◽  
A. R. Payne
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Large Scale ◽  
Plant Cover ◽  
Sediment Deposition ◽  
Natural Phenomenon ◽  
Percent Cover ◽  
Sediment Thickness ◽  
Sediment Accretion ◽  
Natural Sediment

In mid-winter 2018, an unprecedented sediment deposition event occurred throughout portions of the Great Marsh in Massachusetts. Evaluation of this event in distinct marsh areas spanning three towns (Essex, Ipswich, and Newbury) revealed deposition covering 29.2 hectares with an average thickness of 30.1±2.1 mm measured shortly after deposition. While sediment deposition helps marshes survive sea level rise by building elevation, effects of such a large-scale deposition on New England marshes are unknown. This natural event provided an opportunity to study effects of large-scale sediment addition on plant cover and soil chemistry, with implications for marsh resilience. Sediment thickness did not differ significantly between winter and summer, indicating sediment is not eroding or compacting. The deposited sediment at each site had similar characteristics to that of the adjacent mudflat (e.g., texture, bivalve shells), suggesting that deposited materials resulted from ice rafting from adjacent flats, a natural phenomenon noted by other authors. Vegetative cover was significantly lower in plots with rafted sediment (75.6±2.3%) than sediment-free controls (93.1±1.6%) after one growing season. When sorted by sediment thickness categories, the low thickness level (1–19 mm) had significantly greater percent cover than medium (20–39 mm) and high (40–90 mm) categories. Given that sediment accretion in the Great Marsh was found to average 2.7 mm per year, the sediment thickness documented herein represents ~11 years of sediment accretion with only a 25% reduction in plant cover, suggesting this natural sediment event will likely increase long-term marsh resilience to sea level rise.

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