Composition and Flux of Holocene Sediments on the Eastern Laptev Sea Shelf, Arctic Siberia

2001 ◽  
Vol 55 (3) ◽  
pp. 344-351 ◽  
Author(s):  
Henning A. Bauch ◽  
Heidemarie Kassens ◽  
Olga D. Naidina ◽  
Martina Kunz-Pirrung ◽  
Jörn Thiede
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
River Mouth ◽  
Sediment Flux ◽  
Sediment Type ◽  
Laptev Sea ◽  
The Core ◽  
Clayey Silt ◽  
Marine Fossils ◽  
Total Sediment

AbstractA 467-cm-long core from the inner shelf of the eastern Laptev Sea provides a depositional history since 9400 cal yr. B.P. The history involves temporal changes in the fluvial runoff as well as postglacial sea-level rise and southward retreat of the coastline. Although the core contains marine fossils back to 8900 cal yr B.P., abundant plant debris in a sandy facies low in the core shows that a river influenced the study site until ∼8100 cal yr B.P. As sea level rose and the distance to the coast increased, this riverine influence diminished gradually and the sediment type changed, by 7400 cal yr B.P., from sandy silt to clayey silt. Although total sediment input decreased in a step-like fashion from 7600 to 4000 cal yr B.P., this interval had the highest average sedimentation rates and the greatest fluxes in most sedimentary components. While this maximum probably resulted from middle Holocene climate warming, the low input of sand to the site after 7400 cal yr B.P. probably resulted from further southward retreat of the coastline and river mouth. Since about 4000 cal yr B.P., total sediment flux has remained rather constant in this part of the Laptev Sea shelf due to a gradual stabilization of the depositional regime after completion of the Holocene sea-level rise.

scholarly journals Long-term challenge to mangrove in the National park Xuanthuy – data released from shallow subsidence monitoring

2018 ◽  
Vol 34 (3) ◽  
Author(s):  
Le Xuan Thuyen
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
National Park ◽  
Low Cost ◽  
River Mouth ◽  
Biosphere Reserve ◽  
The United States ◽  
Red River ◽  
United States Geological Survey ◽  
The Core

A small mangrove colony growing for several decades on a mud flat on the left side of Balat River mouth has become today a large and healthy forest, containing a high ecosystem service value in the core of the Red River biosphere reserve. As a pioneer ecosystem located at land– water interface in the tropic, there exist always risks to mangroves, especially due to climate change and sea level rise. Sea level rise is a worldwide process, but subsidence is a local problem that can exacerbate these geo-hazards. A monitoring of shallow subsidence has been carried out by using SET-MH technique (developed by the United States Geological Survey) to track the both accretion and land sinking in the core zone of the National Park. The measurement shows the average sedimentation rate of 2.9 cm / yr and the sinking rate of 3.4 cm / yr, since Dec. 30th 2012. This is the first ground-based observation of shallow subsidence under mangroves in the Tonkin Gulf. As a simple and low cost method, so further expansion of this monitoring could provide more useful information to help identify the generally sinking trend of coastal areas in the Red River Delta and also to protect its own biosphere reserve.

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>

Sediment storage, sea level, and sediment delivery to the ocean by coastal plain rivers

2006 ◽  
Vol 30 (4) ◽  
pp. 513-530 ◽  
Author(s):  
Jonathan D. Phillips ◽  
Michael C. Slattery
Keyword(s):  
Sea Level ◽  
Coastal Plain ◽  
River Mouth ◽  
Sediment Flux ◽  
Coastal Plains ◽  
Sediment Storage ◽  
Sediment Yields ◽  
Accommodation Space ◽  
Lower Coastal Plain ◽  
Coastal Plain Rivers

Coastal and marine sedimentary archives are sometimes used as indicators of changes in continental sediment production and fluvial sediment transport, but rivers crossing coastal plains may not be efficient conveyors of sediment to the coast. Where this is the case, changes in continental sediment dynamics are not evident at the river mouth. Stream power is typically low and accommodation space high in coastal plain river reaches, resulting in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. In some cases there is a net loss of sediment in lower coastal plain reaches, so that sediment input from upstream exceeds yield at the river mouth. The lowermost sediment sampling stations on many rivers are too far upstream of the coast to represent lower coastal plain sediment fluxes, and thus tend to overestimate sediment yields. Sediment which does reach the river mouth is often trapped in estuaries and deltas. Assessment of sediment flux from coastal plain rivers is also confounded by the deceptively simple question of the location of the mouth of the river. On low-gradient coastal plains and shelves, the location of the river mouth may have varied by hundreds of kilometers due to sea-level change. The mouth may also differ substantially according to whether it is defined based on channel morphology, network morphology, hydrographic or hydrochemical criteria, elevation of the channel relative to sea level, or the locus of deposition. Further, while direct continent-to-ocean flux may be very low at current sea-level stands, sediment stored in estuaries and lower coastal plain alluvium (including deltas) may eventually become part of the marine sedimentary package. The role of accommodation space in coastal plain alluvial sediment storage has been emphasized in previous work, but low transport capacity controlled largely by slope is also a crucial factor, as we illustrate with examples from Texas.

Relative sea-level changes and the development of a Cambrian transgression

1993 ◽  
Vol 130 (2) ◽  
pp. 245-256 ◽  
Author(s):  
T. McKie
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Yield ◽  
Sediment Flux ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Fluvial Sediment ◽  
Accommodation Space ◽  
Condensed Section ◽  
Lower Palaeozoic

AbstractThe Lower Cambrian in northwest Scotland is one example of a Lower Palaeozoic ‘orthoquartzite-carbonate’ succession deposited on a slowly subsiding, peneplained Precambrian basement during a period of relative sea-level rise. This particular setting led to the development of a very wide, low gradient shelf which was extremely sensitive to minor sea-level changes. The basal quartz arenite section (Lower Member-Pipe Rock) is a transgressive, tide-dominated systems tract, but lacks a systematic parasequence architecture because of three factors: a fluvial sediment flux was insufficient to induce shoreline progradation, accommodation space was limited during sea-level falls (which are commonly expressed by widespread erosional surfaces), and sediment yield to the shelf by transgressive reworking was a major contributor towards the preserved stratigraphy. The storm-dominated Fucoid Beds represent a condensed section and also show the effects of rapid and widespread facies belt oscillations because of the low shelf gradient. An overlying highstand systems tract is also lacking, partly due to the absence of a large fluvial sediment yield and also due to lowstand and transgressive reworking. An erosively based tidal sandsheet at the top of the Fucoid Beds, interpreted to be a lowstand systems tract, therefore rests directly on the condensed section of the underlying sequence. This was in turn reworked into linear tidal sandbanks (Salterella Grit) during slow sea-level rise, prior to the next major transgression. The limited accommodation space therefore introduced a preservational bias towards deepening-upward trends on a parasequence and sequence scale. The oscillations in facies belts, episodic subareal exposure and the potential to remove substantial portions of systems tracts suggests that Lower Palaeozoic ‘orthoquartzite’ successions may exhibit regular and abrupt vertical shifts in depositional environment which, given their subtle lithological character, may require detailed analysis to identify. Such successions may also display incomplete development of several components of transgressive-regressive sequence architecture.

scholarly journals Relative Sea-Level Rise Scenario for 2100 along the Coast of South Eastern Sicily (Italy) by InSAR Data, Satellite Images and High-Resolution Topography

2021 ◽  
Vol 13 (6) ◽  
pp. 1108
Author(s):  
Marco Anzidei ◽  
Giovanni Scicchitano ◽  
Giovanni Scardino ◽  
Christian Bignami ◽  
Cristiano Tolomei ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Land Subsidence ◽  
Salt Marshes ◽  
Satellite Images ◽  
Morphological Changes ◽  
River Mouth ◽  
South Eastern ◽  
Rcp 8.5 ◽  
Coastal Retreat

The global sea-level rise (SLR) projections for the next few decades are the basis for developing flooding maps that depict the expected hazard scenarios. However, the spatially variable land subsidence has generally not been considered in the current projections. In this study, we use geodetic data from global navigation satellite system (GNSS), synthetic aperture radar interferometric measurements (InSAR) and sea-level data from tidal stations to show the combined effects of land subsidence and SLR along the coast between Catania and Marzamemi, in south-eastern Sicily (southern Italy). This is one of the most active tectonic areas of the Mediterranean basin, which drives accelerated SLR, continuous coastal retreat and increasing effects of flooding and storms surges. We focus on six selected areas, which show valuable coastal infrastructures and natural reserves where the expected SLR in the next few years could be a potential cause of significant land flooding and morphological changes of the coastal strip. Through a multidisciplinary study, the multi-temporal flooding scenarios until 2100, have been estimated. Results are based on the spatially variable rates of vertical land movements (VLM), the topographic features of the area provided by airborne Light Detection And Ranging (LiDAR) data and the Intergovernmental Panel on Climate Change (IPCC) projections of SLR in the Representative Concentration Pathways RCP 2.6 and RCP 8.5 emission scenarios. In addition, from the analysis of the time series of optical satellite images, a coastal retreat up to 70 m has been observed at the Ciane river mouth (Siracusa) in the time span 2001–2019. Our results show a diffuse land subsidence locally exceeding 10 ± 2.5 mm/year in some areas, due to compacting artificial landfill, salt marshes and Holocene soft deposits. Given ongoing land subsidence, a high end of RSLR in the RCP 8.5 at 0.52 ± 0.05 m and 1.52 ± 0.13 m is expected for 2050 AD and 2100 AD, respectively, with an exposed area of about 9.7 km2 that will be vulnerable to inundation in the next 80 years.

scholarly journals Monitoring and predicting the shoreline change in Can Gio area in condition of the sea level rise

2014 ◽  
Vol 17 (3) ◽  
pp. 45-53
Author(s):  
Vinh Trong Bui ◽  
Tin Trung Huynh ◽  
Trinh Nguyen Doan Le ◽  
Hoang Minh Ly ◽  
Phong Thanh Le ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Satellite Image ◽  
River Mouth ◽  
Shoreline Change ◽  
Beach Erosion ◽  
Surface Erosion ◽  
Coastal Morphology ◽  
Shoreline Changes ◽  
Seasonal Movement

Locating on the domestic and international navigation routes (Long Tau-Tac Dinh Cau route, Soai Rap route) the Can Gio area is impacted by waterway traffic activities. The seasonal movement of sand bars on the Can Gio is significantly impacted by hydrodynamic of the river mouth. With the important roles of the area, the authors consider the coastal morphology processes under the hydrodynamic. In this paper, the authors has inherited previous studies combined the satellite image analysis to detect the shoreline changes from 1973 to 2013. Besides, numerical modeling was also applied to predict the shoreline changes under impacts of the sea level rise. Results show that, the Can Gio shoreline prolonging from Can Thanh to Dong Hoa is seriously eroded, with average of 7-10 m/year, maximum to 15 m/year. It is found that, beach erosion at Can Gio is a kind of surface erosion impacted by human trigger (shrimp ponds, beach encroachment…). In addition, natural factors (wave, long-shore current, littoral materials) also contribute to increase the erosion rate. Predicted results with sea level rise scenarios show that, the Dong Hoa and Can Thanh will be seriously eroded while the 30-4 beach will be annually deposited.

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

2017 ◽  
Author(s):  
Eveline Christien van der Deijl ◽  
Marcel van der Perk ◽  
Hans Middelkoop
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Budget ◽  
Sediment Dynamics ◽  
Created Wetlands ◽  
River Rhine ◽  
Flow Paths ◽  
Soil Subsidence ◽  
Elevation Data ◽  
Total Sediment

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 aggradation, 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 aggradation and erosion in newly created wetlands. We quantified both the magnitude and spatial patterns of aggradation 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. Aggradation 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. At the intertidal flats, sand aggradation especially takes place at low lying locations close to the channels. Mud aggradation 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. Cut bank retreat 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 aggradation rates over time, but the overall result of this study indicate that the area functions as a sediment trap. On average, the area traps approximately 46 % of the sediment delivered to the study area, which is approximately 3 % of the sediment load of the River Rhine at the Dutch-German border. The total sediment budget of the study area amounts to 29.7 × 103 m3 year−1, which corresponds to a net area-averaged aggradation rate of 5.1 mm year−1. This is enough to compensate for the actual rates of sea level rise and soil subsidence in The Netherlands.

scholarly journals Impacts of Sea Level Rise and River Discharge on the Hydrodynamics Characteristics of Jakarta Bay (Indonesia)

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1384 ◽  
Author(s):  
Martin Yahya Surya ◽  
Zhiguo He ◽  
Yuezhang Xia ◽  
Li Li
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
River Discharge ◽  
River Mouth ◽  
Ocean Model ◽  
Phase Lag ◽  
Tidal Component ◽  
Inundation Area ◽  
Current Magnitude ◽  
Coastal Ocean Model

Jakarta city has been vulnerable to sea level rise and flooding for many years. A Giant Seawall (GSW) was proposed in Jakarta Bay to protect the city. The impacts of sea level rise and river discharge on the tidal dynamics in Jakarta Bay and flooding areas in Jakarta city were investigated using the finite-volume coastal ocean model (FVCOM). Model results showed that the bay is diurnally dominated by the K1 tidal component. The diurnal tides propagate westward, while the semidiurnal tides propagate eastward in the bay. The rise of sea level increases the diurnal tidal component and the inundation areas due to the increased tidal forcing: when considering a sea level rise of 0.6 m, the K1 amplitude increases by ~1% (0.25 cm) near the coastline and the current magnitude increases by 16.6% (0.05 m/s). The inundation area increases with the sea level rise in the low land elevation areas occurring near the coastlines: the inundation area increased by 29.68 km2 (7.1%) with a sea level rise of 0.6 m. The increase of river discharge amplified the diurnal tidal component as well as the inundation areas at the river mouth due to increased fluvial forcing: if 10 times the mean river discharge occurs, the K1 amplitude increases by ~1% (0.25 cm) and the current magnitude increases by 100% (0.4 m/s), and the inundation areas increase by 26.61 km2 (6.2%). The K1 tidal phase remains almost unchanged under both the sea level rise and river discharge conditions. The combined increase of sea level rise and the river discharge amplifies the inundation areas and the tidal currents due to increased tidal and fluvial forcing. The construction of GSW would decrease the tidal prism and dissipation effects of the bay, thus slightly increasing the K1 amplitude of the tidal level: by less than 1% (0.2 cm). There would be no significant change of phase lag for the K1 component. Although this study is site specific, the findings could be applied more widely to any open-type bays.

scholarly journals Sea-level rise along the Emilia-Romagna coast (Northern Italy) at 2100: scenarios and impacts

2017 ◽  
Author(s):  
Luisa Perini ◽  
Lorenzo Calabrese ◽  
Paolo Luciani ◽  
Marco Olivieri ◽  
Gaia Galassi ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Land Subsidence ◽  
Coastal Plain ◽  
River Mouth ◽  
Northern Italy ◽  
Po River ◽  
Mitigation And Adaptation ◽  
The Impact

Abstract. As a consequence of climate change and human-induced land subsidence, coastal zones are directly impacted by sea-level rise. In some particular areas, the effects on the ecosystem and the urbanisation are particularly enhanced. We focus on the Emilia-Romagna coastal plain in Northern Italy, bounded by the Po river mouth to the north and by the Apennines to the south. The plain is ~ 130 km long and is characterised by wide areas below sea level, in part reclaimed wetlands. In this context, several morphodynamic factors make the shore and back-shore unstable. During next decades, the combined effects of land subsidence and of the sea-level rise in consequence of climate change are expected to enhance the shoreline instability, leading to a further retreat. The consequent loss of beaches would impact the economy of the region, tightly connected with tourism infrastructures. Furthermore, the loss of wetlands and dunes would threaten the ecosystem, crucial for the preservation of life and environment. These specific conditions show the importance of a precise definition of the possible local impacts of the ongoing and future climate variations. The aim of this work is the characterisation of vulnerability in different sectors of the coastal plain and the recognition of the areas in which human intervention is urgently required. The IPCC AR5 sea-level scenarios are merged with new high resolution terrain models, current data for local subsidence and predictions of a flooding model (in_CoastFlood) to develop different scenarios for the impact of sea-level rise to year 2100. First, the potential land loss due to the combined effect of subsidence and sea-level rise is extrapolated. Second, the increase of floodable areas in consequence of storm surges is quantitatively determined. The results are expected to support the regional mitigation and adaptation strategies designed in response to climate change.

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