Fluvial Sediment Supply and Relative Sea-Level Rise

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

10.5194/egusphere-egu21-5140 ◽

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>

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Sedimentation and Survival of the Mekong Delta: A Case Study of Decreased Sediment Supply and Accelerating Rates of Relative Sea Level Rise

Oceanography ◽

10.5670/oceanog.2017.318 ◽

2017 ◽

Vol 30 (3) ◽

pp. 98-109 ◽

Cited By ~ 18

Author(s):

Mead Allison ◽

◽

Charles Nittrouer ◽

Andrea Ogston ◽

Julia Mullarney ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Mekong Delta ◽

Sediment Supply ◽

Relative Sea Level ◽

Relative Sea Level Rise

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The interplay between relative sea-level rise and sediment supply at the distal part of the Nile littoral cell

The Holocene ◽

10.1177/0959683615608687 ◽

2015 ◽

Vol 26 (2) ◽

pp. 248-264 ◽

Cited By ~ 5

Author(s):

Hadar Elyashiv ◽

Revital Bookman ◽

Dov Zviely ◽

Simona Avnaim-Katav ◽

Amir Sandler ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Distal Part ◽

Sediment Supply ◽

Relative Sea Level ◽

Littoral Cell ◽

Relative Sea Level Rise

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The role of relative sea-level rise and changing sediment supply on Holocene gravel barrier development: the example of Porlock, Somerset, UK

The Holocene ◽

10.1191/095968398667901806 ◽

1998 ◽

Vol 8 (2) ◽

pp. 165-181 ◽

Cited By ~ 42

Author(s):

S. Jennings ◽

J. D. Orford ◽

M. Canti ◽

R. J. N. Devoy ◽

V. Straker

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Sediment Supply ◽

Relative Sea Level ◽

Relative Sea Level Rise

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The Holocene evolution of the barrier and the back-barrier basins of Belgium and the Netherlands as a function of late Weichselian morphology, relative sea-level rise and sediment supply

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/s0016774600021533 ◽

2000 ◽

Vol 79 (1) ◽

pp. 3-16 ◽

Cited By ~ 124

Author(s):

Dirk J. Beets ◽

Adam J. F. van der Spek

Keyword(s):

The Netherlands ◽

Sea Level Rise ◽

Sea Level ◽

Middle Ages ◽

North Sea ◽

Sediment Supply ◽

Relative Sea Level ◽

The North ◽

Relative Sea Level Rise ◽

The North Sea

AbstractFlooding of the southern part of the North Sea occurred between 9000 and 8000 BP, when the rate of relative sea-level rise was on the order of 0.7 cm per year for the Dover Strait Region and 1.6 cm per year for the area north of the Frisian Islands, forcing the shoreline to recede rapidly. When relative sea-level rise decelerated after 7000 BP for the Belgian coast and 6000 BP for the central Netherlands coast, sediment supply by the tidal currents balanced the creation of accommodation space in the estuaries and other back-barrier basins. Consequently, the barrier started to stabilize, and the tidal basins and their inlets silted up. Between 5500 and 4500 BP, the Belgian coastal plain changed into a freshwater marsh with peat accumulation, and the same happened 500–1000 years later in the western provinces of the Netherlands. The E-W running barrier/back-barrier system of the Frisian Islands in the northern Netherlands stayed open until today, however, because of lower sediment supply.The period between 4000 and 2000 BP was relatively quiet due to the strong deceleration of the rate of sea-level rise; peat cushions developed behind the barriers, which were straightened by erosion of the headlands. Major and often catastrophic flooding occurred in the Middle Ages, when the estuaries in the southwestern part of the Netherlands formed.About 226 (± 15%) × 109 m3 sediment, mostly sand, is stored in the barriers and back-barrier basins of the Netherlands, 70% of which was deposited prior to 5000 BP. About 10% of the stored sediment is estimated to be of alluvial origin. Most of the sediment is derived by the erosion of the Pleistocene basement during recession of the barriers, but tide-induced crossshore transport from the North Sea forms an additional source for the barriers and back-barriers of the west-facing coast of the Netherlands.

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Late Quaternary sequence stratigraphy of the Mackenzie Delta

Canadian Journal of Earth Sciences ◽

10.1139/e96-081 ◽

1996 ◽

Vol 33 (7) ◽

pp. 1053-1074 ◽

Cited By ~ 16

Author(s):

Philip R Hill

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Sequence Stratigraphy ◽

Late Quaternary ◽

Sediment Supply ◽

Mackenzie Delta ◽

Relative Sea Level ◽

Relative Sea Level Rise ◽

Healing Phase ◽

Late Wisconsinan

The Late Wisconsinan and Holocene sequence stratigraphy of the Mackenzie Delta provides insights into the glacial history of the region. The base of the described succession is a hummocky regional reflector interpreted to be a flooding surface formed immediately after retreat of glacial ice from the Mackenzie Trough. Above this flooding surface, two progradational parasequences are present. The first, assigned to the transgressive systems tract, is correlated with the Tutsieta Lake readvance of the ice sheet at approximately 13 000 BP. A flooding surface forming the upper boundary of this parasequence extends inland to at least Inuvik, developing as a response to glacial retreat and early Holocene relative sea level rise. The second parasequence of Holocene deltaic deposits is assigned to the highstand systems tract and is characterized by progressive progradation of the delta into the Mackenzie Trough to a position seaward of the present delta coastline. A distinct reduction in gradient of the most recent delta clinoforms is consistent with other data suggesting regional transgression and is interpreted to represent the development of a healing-phase wedge. The reasons for this recent transgression are not clear, because relative sea level rise has decreased and sediment supply probably increased over the last 2000 years. Transgression may be related to decreased efficiency of channels, increased trapping of sediments by thermokarst lakes, overspill of the delta across the eastern margin of the valley, and (or) progressively greater exposure to wave action as the delta became less sheltered by the confines of the glacial valley.

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Accelerated river avulsion frequency on lowland deltas due to sea-level rise

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1912351117 ◽

2020 ◽

Vol 117 (30) ◽

pp. 17584-17590 ◽

Cited By ~ 3

Author(s):

Austin J. Chadwick ◽

Michael P. Lamb ◽

Vamsi Ganti

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Global Climate ◽

Sediment Supply ◽

Flood Hazards ◽

Relative Sea Level ◽

River Deltas ◽

Abrupt Changes ◽

Relative Sea Level Rise ◽

Coastal Land

Sea-level rise, subsidence, and reduced fluvial sediment supply are causing river deltas to drown worldwide, affecting ecosystems and billions of people. Abrupt changes in river course, called avulsions, naturally nourish sinking land with sediment; however, they also create catastrophic flood hazards. Existing observations and models conflict on whether the occurrence of avulsions will change due to relative sea-level rise, hampering the ability to forecast delta response to global climate change. Here, we combined theory, numerical modeling, and field observations to develop a mechanistic framework to predict avulsion frequency on deltas with multiple self-formed lobes that scale with backwater hydrodynamics. Results show that avulsion frequency is controlled by the competition between relative sea-level rise and sediment supply that drives lobe progradation. We find that most large deltas are experiencing sufficiently low progradation rates such that relative sea-level rise enhances aggradation rates—accelerating avulsion frequency and associated hazards compared to preindustrial conditions. Some deltas may face even greater risk; if relative sea-level rise significantly outpaces sediment supply, then avulsion frequency is maximized, delta plains drown, and avulsion locations shift inland, posing new hazards to upstream communities. Results indicate that managed deltas can support more frequent engineered avulsions to recover sinking land; however, there is a threshold beyond which coastal land will be lost, and mitigation efforts should shift upstream.

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Submergence, nutrient enrichment, and tropical storm impacts on Spartina alterniflora in the microtidal northern Gulf of Mexico

Marine Ecology Progress Series ◽

10.3354/meps13342 ◽

2020 ◽

Vol 644 ◽

pp. 33-45

Author(s):

JM Hill ◽

PS Petraitis ◽

KL Heck

Keyword(s):

Gulf Of Mexico ◽

Sea Level Rise ◽

Sea Level ◽

Spartina Alterniflora ◽

Anthropogenic Impacts ◽

Interactive Effects ◽

Relative Sea Level ◽

Hurricane Disturbance ◽

Submergence Stress ◽

Relative Sea Level Rise

Salt marshes face chronic anthropogenic impacts such as relative sea level rise and eutrophication, as well as acute disturbances from tropical storms that can affect the productivity of these important communities. However, it is not well understood how marshes already subjected to eutrophication and sea level rise will respond to added effects of episodic storms such as hurricanes. We examined the interactive effects of nutrient addition, sea level rise, and a hurricane on the growth, biomass accumulation, and resilience of the saltmarsh cordgrass Spartina alterniflora in the Gulf of Mexico. In a microtidal marsh, we manipulated nutrient levels and submergence using marsh organs in which cordgrasses were planted at differing intertidal elevations and measured the impacts of Hurricane Isaac, which occurred during the experiment. Prior to the hurricane, grasses at intermediate and high elevations increased in abundance. After the hurricane, all treatments lost approximately 50% of their shoots, demonstrating that added nutrients and elevation did not provide resistance to hurricane disturbance. At the end of the experiment, only the highest elevations had been resilient to the hurricane, with increased above- and belowground growth. Added nutrients provided a modest increase in above- and belowground growth, but only at the highest elevations, suggesting that only elevation will enhance resilience to hurricane disturbance. These results empirically demonstrate that S. alterniflora in microtidal locations already subjected to submergence stress is less able to recover from storm disturbance and suggests we may be underestimating the loss of northern Gulf Coast marshes due to relative sea level rise.

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