Investigating land subsidence of transitional environments

2020 ◽  
Author(s):  
Claudia Zoccarato ◽  
Eugenia Parrella
Keyword(s):  
Sea Level ◽  
Land Subsidence ◽  
Test Duration ◽  
Large Contribution ◽  
Loading Test ◽  
Mean Sea Level ◽  
The Holocene ◽  
Geomechanical Properties ◽  
Holocene Sediments ◽  
Transitional Environments

<p>Lagoons and deltas are characterized by the presence of transitional environments, such as low-lying plains or islands, salt marshes, and tidal flats with fundamental value in terms of biodiversity, recreational activities, and protection of inland territories from storms. The fate of these morphological landforms is severely threatened by the ongoing rise of the mean sea level (SLR) and land subsidence (LS). The loss of elevation relative to mean sea level, i.e. SLR plus LS, must be counterbalanced by accretion of inorganic sediments and biodegradation of organic matter. A large contribution to LS of transitional landforms is due to auto-compaction of the Holocene sediments. In fact, the large porosity and compressibility of these recent deposits, especially when the organic fraction is high, are responsible for a significant thickness reduction because of consolidation when new deposition occurs on the surface. SAR interferometry on deep-founded and surface radar scatterers, ground-based monitoring equipment (deep levelling benchmarks, SET, accretion traps), and a novel in-situ loading test have been used in the Venice Lagoon to distinguish between deep and shallow LS contributions, i.e. LS occurring below and above the Pleistocene / Holocene bound. After a review of the available dataset, the present contribution describes the modelling activities that are ongoing to understand the collected measurements. In particular, an advance coupled mixed finite-element poromechanical model is used to reproduce the loading test carried out on the Lazzaretto Nuovo marshland on summer 2019. With the aim of reliably characterize the geomechanical properties of the Holocene sediments of the tidal-marsh, a number of plastic tanks were filled with seawater, reaching a cumulative load of 40 kN applied on a 2.5´1.8 m<sup>2</sup> surface. Specific instrumentations were deployed before positioning the tanks to measure soil vertical displacement and pore overpressure at various depths below the load and distances from the load center. The numerical model uses linear piecewise polynomials and the lowest order Raviart–Thomas mixed space to represent the three-dimensional porous medium motion and the groundwater flow rate, respectively. The model is applied to the various loading and unloading phases that superpose to the tidal fluctuation of the lagoon level recorded over the 4-day test duration. The geomechanical properties thus derived constitute a significant advancement to understand the LS drivers in transitional environments and predict their resilience to SLR.    </p>

Decompacting Holocene deltas to quantify their (proper) weight

2021 ◽  
Author(s):  
Anita Rigoni ◽  
Philip S. J. Minderhoud ◽  
Claudia Zoccarato ◽  
Pietro Teatini
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Land Subsidence ◽  
Specific Weight ◽  
Depositional Environments ◽  
Anthropogenic Pressures ◽  
Large Variability ◽  
The Holocene ◽  
Geomechanical Properties ◽  
Proper Weight

<p>Most of the world major deltas are threatened by relative sea level rise, i.e. land subsidence and sea level rise, caused by a combination of anthropogenic pressures and natural processes. This study focuses on the natural components of land subsidence directly and indirectly related to the Holocene delta stratigraphy. Firstly, subsidence is caused by natural compaction of the Holocene sediments following deposition over time under their own weight. Secondly, subsidence is caused by the visco-elastic deformation of the Earth crust driven by cumulative load of the Holocene delta (so-called Sediment Isostatic Adjustment). These two processes are obviously connected and call for a proper evaluation of the weight of (the Holocene portion of) a delta. This requires a proper quantification of specific weight and degree of compaction of Holocene deposits with depth to arrive at a first-order assessment of Holocene delta weight.</p><p> </p><p>This study proposes an innovative methodology to address the following two questions: 1) What is the proper weight of a (Holocene) delta? 2) How much have deposits been compacted since their deposition during Holocene delta formation? Our approach integrates knowledge and data on deltaic depositional environments, stratigraphic information, geomechanical properties and other characteristics of the Holocene sequence. </p><p> </p><p>The developed approach is applied to eight major deltas worldwide selected from a larger database according to the availability of lithostratigraphic and geomechanical information. The analysis is conducted at the scale of an entire delta, thus required the upscaling and interpolation of datasets generally available from a few wellbores only. Lithostratigraphic data  is combined with a backwards modelling procedure to decompact the Holocene delta sequence to their decompacted thickness to provide a proper  estimation of their weight, which takes into account the (computed) in-situ compaction degree. The results show a large variability in compaction and specific weight distribution for the different deltas which underscores the substantial role of natural compaction on delta evolution. </p>

The mid-Holocene sea-level highstand at Bogenfels Pan on the southwest coast of Namibia

2006 ◽  
Vol 66 (2) ◽  
pp. 303-310 ◽  
Author(s):  
John S. Compton
Keyword(s):  
Sea Level ◽  
Southern Africa ◽  
Before Present ◽  
Southern Coast ◽  
Mollusc Shell ◽  
Mean Sea Level ◽  
The Holocene ◽  
Longshore Drift ◽  
Rapid Emergence ◽  
Holocene Sea Level

AbstractThe radiocarbon ages of mollusc shells from the Bogenfels Pan on the hyper arid southern coast of Namibia provide constraints on the Holocene evolution of sea level and in particular, the mid-Holocene highstand. The Bogenfels Pan was flooded to depths of 3 m above mean sea level (amsl) to form a large subtidal lagoon from 7300 to 6500 calibrated radiocarbon years before present (cal yr BP). The mollusc assemblage of the wave sheltered lagoon includes Nassarius plicatellus, Lutraria lutraria, and the bivalves Solen capensis and Gastrana matadoa, both of which no longer live along the wave-dominated southern Namibian coast. The radiocarbon ages of mollusc shell from a gravely beach deposit exposed in a diamond exploration trench indicate that sea level fell to near or 1 m below its present-day position between 6500 and 4900 cal yr BP. The rapid emergence of the pan between 6500 and 4900 cal yr BP exceeds that predicted by glacio-isostatic models and may indicate a 3-m eustatic lowering of sea level. The beach deposits at Bogenfels indicate that sea level rose to 1 m amsl between 4800 and 4600 cal yr BP and then fell briefly between 4600 and 4200 cal yr BP before returning to 1 m amsl. Since 4200 cal yr BP sea level has remained within one meter of the present-day level and the beach at Bogenfels has prograded seaward from the delayed arrival of sand by longshore drift from the Orange River. A 6200 cal yr BP coastal midden and a 600 cal yr BP midden 1.7 km from the coast indicate sporadic human utilization of the area. The results of this study are consistent with previous studies and help to refine the Holocene sea-level record for southern Africa.

scholarly journals Land subsidence and aquifer compaction in Montgomery County, Texas, U.S.: 2000–2020

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Kuan Wang ◽  
Guoquan Wang ◽  
Brendan Cornelison ◽  
Hanlin Liu ◽  
Yan Bao
Keyword(s):  
Sea Level ◽  
Land Subsidence ◽  
Groundwater Level ◽  
Groundwater Withdrawal ◽  
Montgomery County ◽  
Mean Sea Level ◽  
Sediment Compaction

AbstractGroundwater-withdrawal-induced land subsidence has been a big concern in Montgomery County, Texas, U.S. since the 2000s. As of 2020, approximately half of the entire county is experiencing subsidence over 5 mm/year. This study aims to investigate ongoing land subsidence in Montgomery County using groundwater-level, extensometer, and GPS datasets. According to this study, land subsidence in Montgomery County since the mid-2000s is primarily contributed by sediment compaction in the Evangeline and Jasper aquifers; the compaction of Jasper aquifer contributes approximately one-third of the land subsidence since the mid-2000s; the pre-consolidation heads of the Chicot, Evangeline, and Jasper aquifers in Montgomery County are close to each other, approximately 15–25 m below mean sea level; the virgin-compaction/head-decline ratio is approximately 1:250 in the Evangeline aquifer and 1:800 in the Jasper aquifer in central and southern Montgomery County. As of 2020, the Jasper groundwater-level altitude is approximately 20–40 m below the pre-consolidation head in the central and southern Montgomery County; the Evangeline groundwater-level altitude is about 40–60 m below the pre-consolidation head. Land subsidence will continue to occur as long as the groundwater-level altitude in either the Evangeline or the Jasper aquifer remains below the pre-consolidation head.

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

CORRELATION OF THE BLACK, MARMARA AND AEGEAN SEAS DURING THE HOLOCENE

2017 ◽  
Author(s):  
Nikolay Esin ◽  
Nikolay Esin ◽  
Vladimir Ocherednik ◽  
Vladimir Ocherednik
Keyword(s):  
Mathematical Model ◽  
Sea Level ◽  
Black Sea ◽  
Aegean Sea ◽  
The Black Sea ◽  
Sea Level Changes ◽  
The Holocene

A mathematical model describing the change in the Black Sea level depending on the Aegean Sea level changes is presented in the article. Calculations have shown that the level of the Black Sea has been repeating the course of the Aegean Sea level for the last at least 6,000 years. And the level of the Black Sea above the Aegean Sea level in the tens of centimeters for this period of time.

scholarly journals Deterministic approach for multiple-source tsunami hazard assessment for Sines, Portugal

2015 ◽  
Vol 15 (11) ◽  
pp. 2557-2568 ◽  
Author(s):  
M. Wronna ◽  
R. Omira ◽  
M. A. Baptista
Keyword(s):  
Sea Level ◽  
Wave Height ◽  
Hazard Assessment ◽  
Test Site ◽  
Tsunami Hazard ◽  
Deterministic Approach ◽  
Flow Depth ◽  
Mean Sea Level ◽  
Tsunami Hazard Assessment ◽  
The Impact

Abstract. In this paper, we present a deterministic approach to tsunami hazard assessment for the city and harbour of Sines, Portugal, one of the test sites of project ASTARTE (Assessment, STrategy And Risk Reduction for Tsunamis in Europe). Sines has one of the most important deep-water ports, which has oil-bearing, petrochemical, liquid-bulk, coal, and container terminals. The port and its industrial infrastructures face the ocean southwest towards the main seismogenic sources. This work considers two different seismic zones: the Southwest Iberian Margin and the Gloria Fault. Within these two regions, we selected a total of six scenarios to assess the tsunami impact at the test site. The tsunami simulations are computed using NSWING, a Non-linear Shallow Water model wIth Nested Grids. In this study, the static effect of tides is analysed for three different tidal stages: MLLW (mean lower low water), MSL (mean sea level), and MHHW (mean higher high water). For each scenario, the tsunami hazard is described by maximum values of wave height, flow depth, drawback, maximum inundation area and run-up. Synthetic waveforms are computed at virtual tide gauges at specific locations outside and inside the harbour. The final results describe the impact at the Sines test site considering the single scenarios at mean sea level, the aggregate scenario, and the influence of the tide on the aggregate scenario. The results confirm the composite source of Horseshoe and Marques de Pombal faults as the worst-case scenario, with wave heights of over 10 m, which reach the coast approximately 22 min after the rupture. It dominates the aggregate scenario by about 60 % of the impact area at the test site, considering maximum wave height and maximum flow depth. The HSMPF scenario inundates a total area of 3.5 km2.

scholarly journals Tropical cyclone simulations over Bangladesh at convection permitting 4.4 km & 1.5 km resolution

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hamish Steptoe ◽  
Nicholas Henry Savage ◽  
Saeed Sadri ◽  
Kate Salmon ◽  
Zubair Maalick ◽  
...  
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Sea Level ◽  
Tropical Cyclones ◽  
Weather Forecasting ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Medium Range ◽  
Gust Speed

AbstractHigh resolution simulations at 4.4 km and 1.5 km resolution have been performed for 12 historical tropical cyclones impacting Bangladesh. We use the European Centre for Medium-Range Weather Forecasting 5th generation Re-Analysis (ERA5) to provide a 9-member ensemble of initial and boundary conditions for the regional configuration of the Met Office Unified Model. The simulations are compared to the original ERA5 data and the International Best Track Archive for Climate Stewardship (IBTrACS) tropical cyclone database for wind speed, gust speed and mean sea-level pressure. The 4.4 km simulations show a typical increase in peak gust speed of 41 to 118 knots relative to ERA5, and a deepening of minimum mean sea-level pressure of up to −27 hPa, relative to ERA5 and IBTrACS data. The downscaled simulations compare more favourably with IBTrACS data than the ERA5 data suggesting tropical cyclone hazards in the ERA5 deterministic output may be underestimated. The dataset is freely available from 10.5281/zenodo.3600201.

scholarly journals Flooding Conditions at Aveiro Port (Portugal) within the Framework of Projected Climate Change

2021 ◽  
Vol 9 (6) ◽  
pp. 595
Author(s):  
Américo Soares Ribeiro ◽  
Carina Lurdes Lopes ◽  
Magda Catarina Sousa ◽  
Moncho Gomez-Gesteira ◽  
João Miguel Dias
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Climate Change Impacts ◽  
Storm Surges ◽  
Historical Period ◽  
Return Periods ◽  
Wave Regime ◽  
Mean Sea Level ◽  
Sea Levels ◽  
Far Future

Ports constitute a significant influence in the economic activity in coastal areas through operations and infrastructures to facilitate land and maritime transport of cargo. Ports are located in a multi-dimensional environment facing ocean and river hazards. Higher warming scenarios indicate Europe’s ports will be exposed to higher risk due to the increase in extreme sea levels (ESL), a combination of the mean sea level, tide, and storm surge. Located on the west Iberia Peninsula, the Aveiro Port is located in a coastal lagoon exposed to ocean and river flows, contributing to higher flood risk. This study aims to assess the flood extent for Aveiro Port for historical (1979–2005), near future (2026–2045), and far future (2081–2099) periods scenarios considering different return periods (10, 25, and 100-year) for the flood drivers, through numerical simulations of the ESL, wave regime, and riverine flows simultaneously. Spatial maps considering the flood extent and calculated area show that most of the port infrastructures' resilience to flooding is found under the historical period, with some marginal floods. Under climate change impacts, the port flood extent gradually increases for higher return periods, where most of the terminals are at high risk of being flooded for the far-future period, whose contribution is primarily due to mean sea-level rise and storm surges.

scholarly journals Approaching Sea-Level Rise (SLR) Change: Strengthening Local Responses to Sea-Level Rise and Coping with Climate Change in Northern Mozambique

2021 ◽  
Vol 9 (2) ◽  
pp. 205
Author(s):  
Serafino Afonso Rui Mucova ◽  
Ulisses Miranda Azeiteiro ◽  
Walter Leal Filho ◽  
Carina Lurdes Lopes ◽  
João Miguel Dias ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Sea Level Rise ◽  
Sea Level ◽  
North Coast ◽  
Coastal Regions ◽  
Mean Sea Level ◽  
Representative Concentration Pathways ◽  
Local Responses ◽  
Ipcc Report ◽  
Global Estimates

Mean sea-level is expected to rise significantly by 2100 in all scenarios, including those compatible with the objectives of the Paris Climate Agreement. Global sea level rise projections indicate devastating implications for populations, ecosystem services and biodiversity. The implications of the sea-level rise (SLR) on low-lying islands and coastal regions and communities are substantial and require deep-rooted coping measures. In the absence of adequate responses for coping, Mozambique is expected to record huge losses, with an impact on the economy and development in many sectors of its coastal regions mainly in northern Mozambique. This research aimed to perform projections on SLR in Mozambique, and to understand its role and implications on the north coast of the country. SLR was estimated through the analysis of model outputs that support the global estimates of the fifth IPCC report near the Mozambican coast, for each of the four representative concentration pathways (RCPs) scenarios. Regional coastline retreat and coastal erosion were estimated through the results of global sandy coastlines projections developed by Vousdoukas. Mean sea-level rise projections indicate that regional estimates for the Mozambican coast are relative higher than global estimates (~0.05 m) for all representative concentration pathways (RCPs). Yet, we highlight significant differences in sea-level rises of 0.5 m, 0.7 m or 1.0 m by 2100 compared to the global mean. It is expected that with the increase in the mean sea level in the northern part of the Mozambican coast, erosive effects will increase, as well as the retreat of the coastline until 2100. With this, the tourism sector, settlements, ecosystem services and local populations are expected to be significantly affected by 2050, with increased threats in 2100 (RCP4.5, RCP8.5). Local responses for coping are proposed and properly discussed for the RCP4.5 and RCP8.5 scenarios through 2100.

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