Coastal development in southwestern Bangladesh: understanding the interplay between storms and sea level rise

Sea-level rise and sediment supply have influenced coastal morphology and sedimentation on Bangladesh’s southwestern Ganges‐Brahmaputra‐Meghna (GBM) delta coast. Satellite images and geological core from the Haringhata coastal region were analyzed to explain the morphological changes and to understand the influences on deposits. The results derived from satellite images indicate that the southern coastline experienced a retreat that ranges between 2.3 and 2.9 km. In contrast, the eastern and western coastline advanced. The erosion and accretion ratio was 0.29 from 1977 to 1989, while the ratio was higher 2.90–4.77 from 1989 to 2020. Two sedimentary facies were identified using 130 cm thick successions. A parallel to wavy laminated bluish gray mud facies of deeper part was deposited in a marine-influenced environment. A planar to hummocky cross stratified, gray to grayish white silty sand facies of storm overwash deposits overlies the mud facies with sharp contacts. Unimodal to bimodal grain distributions of sandy sediments suggest two sources: sand derived from the beach and mud carried by adjacent tidal rivers and resuspended offshore sediment. Coastline dynamics and sedimentation of the area were influenced by inequality of accommodation and sediment supply ratio in the river mouth. This occurs due to sea-level rise and deficit in upstream water and sediment discharge. Morphological change along the southwestern GBM delta coast was not only caused by wave energy, but also by rising sea levels which shifted sediment accommodation space landward.

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

Remote Sensing ◽

10.3390/rs13061108 ◽

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.

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Relative sea-level rise scenario for 2100 along the coasts of south eastern Sicily by GNSS and InSAR data, satellite images and high-resolution topography

10.5194/egusphere-egu21-2889 ◽

2021 ◽

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 ◽

Intergovernmental Panel ◽

South Eastern ◽

Coastal Retreat

The global sea-level rise (SLR) projections for the next 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 subsidence rates 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 is affected to 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 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 RCP2.6 and RCP8.5 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 &#177; 2.0 mm/yr-1 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 RCP8.5 at 0.52&#177; 0.05 m and 1.52&#177;0.13 m is expected for 2050 AD and 2100 AD, respectively, with a projected area of about 9.7 km2 that will be vulnerable to inundation in the next 80 years.

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Assessment of island beach erosion due to sea level rise: the case of the Aegean archipelago (Eastern Mediterranean)

Natural Hazards and Earth System Science ◽

10.5194/nhess-17-449-2017 ◽

2017 ◽

Vol 17 (3) ◽

pp. 449-466 ◽

Cited By ~ 20

Author(s):

Isavela N. Monioudi ◽

Adonis F. Velegrakis ◽

Antonis E. Chatzipavlis ◽

Anastasios Rigos ◽

Theophanis Karambas ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Spatial Information ◽

Eastern Mediterranean ◽

Sediment Supply ◽

Coastal Development ◽

Beach Erosion ◽

Coastal Protection ◽

Intergovernmental Panel ◽

Economic Resource

Abstract. The present contribution constitutes the first comprehensive attempt to (a) record the spatial characteristics of the beaches of the Aegean archipelago (Greece), a critical resource for both the local and national economy, and (b) provide a rapid assessment of the impacts of the long-term and episodic sea level rise (SLR) under different scenarios. Spatial information and other attributes (e.g., presence of coastal protection works and backshore development) of the beaches of the 58 largest islands of the archipelago were obtained on the basis of remote-sensed images available on the web. Ranges of SLR-induced beach retreats under different morphological, sedimentological and hydrodynamic forcing, and SLR scenarios were estimated using suitable ensembles of cross-shore (1-D) morphodynamic models. These ranges, combined with empirically derived estimations of wave run-up induced flooding, were then compared with the recorded maximum beach widths to provide ranges of retreat/erosion and flooding at the archipelago scale. The spatial information shows that the Aegean pocket beaches may be particularly vulnerable to mean sea level rise (MSLR) and episodic SLRs due to (i) their narrow widths (about 59 % of the beaches have maximum widths < 20 m), (ii) their limited terrestrial sediment supply, (iii) the substantial coastal development and (iv) the limited existing coastal protection. Modeling results indeed project severe impacts under mean and episodic SLRs, which by 2100 could be devastating. For example, under MSLR of 0.5 m – representative concentration pathway (RCP) 4.5 of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate change (IPCC) – a storm-induced sea level rise of 0.6 m is projected to result in a complete erosion of between 31 and 88 % of all beaches (29–87 % of beaches are currently fronting coastal infrastructure and assets), at least temporarily. Our results suggest a very considerable risk which will require significant effort, financial resources and policies/regulation in order to protect/maintain the critical economic resource of the Aegean archipelago.

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Climate Change and Man-made Interventions, as Destabilizing Factors of the Coastal Zone: Some Examples of Coasts and Coastal Wetlands in Urban, Peri-Urban Areas and Natural Parks in Greece

International Journal of Environment and Climate Change ◽

10.9734/ijecc/2019/v9i1130144 ◽

2019 ◽

pp. 616-642

Author(s):

Aristeidis Mertzanis ◽

Asimina Mertzani

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

Urban Areas ◽

Coastal Erosion ◽

River Mouth ◽

Coastal Development ◽

Aerial Photographs ◽

Rapid Urbanization ◽

Natural Parks

The consequences of man-made interventions, Climate Change and future Sea-level rise upon some coastal plains of Greece are examined. Many urban, peri-urban areas and Natural Parks, in low elevation coastal zones in Greece are experiencing or are at risk of Sea-level rise, storm surges, water and soil pollution, saline water intrusion (salinity), coastal erosion and shoreline retreat, floods, and droughts. Sea-level rise could erode and inundate coastal ecosystems and disrupt wetlands, Urban and peri-Urban areas. Characteristic examples of these are the protected wetlands that exist in Greece such as those in the Delta and the river mouth areas of the Sperchios, Alfeios, Arachthos, Louros, and Inois rivers, and the small town of Tolo. Man-made interventions affect the coastal wetland ecosystems, Urban and peri-Urban areas under study. At the same time, an important factor of the destabilization of the ecological balance is the Climate Change and the expected sea-level rise. The main anthropogenic degradation and stresses on the under investigation areas, in recent decades, includes wetland draining, exsiccation of lagoons and lakes, river engineering works, dam construction, intensification and development of agriculture projects, sand mining from riverbeds and beaches, construction of motorways, construction of harbor structures, such as harbors, jetties, seawalls, groins, and breakwaters, rapid urbanization processes, holiday home building and tourist facilities, massive tourism and intense coastal development, water pollution, human-induced land subsidence (uncontrolled water abstraction from surface and underground water tables), and removal of coastal vegetation. Satellite images, maps and systematic in situ observations, integrated with the direct digitizing on the basis of different aged aerial photographs was adopted to estimate the coastal erosion and accretion rates in recent decades (1945-2019) in the areas, under study.

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Contributions of Organic and Mineral Matter to Vertical Accretion in Tidal Wetlands across a Chesapeake Bay Subestuary

Journal of Marine Science and Engineering ◽

10.3390/jmse9070751 ◽

2021 ◽

Vol 9 (7) ◽

pp. 751

Author(s):

Jenny R. Allen ◽

Jeffrey C. Cornwell ◽

Andrew H. Baldwin

Keyword(s):

Organic Matter ◽

Sea Level Rise ◽

Chesapeake Bay ◽

Sea Level ◽

210Pb Dating ◽

Sediment Supply ◽

Mineral Matter ◽

Tidal Wetlands ◽

Vertical Accretion ◽

Inorganic Matter

Persistence of tidal wetlands under conditions of sea level rise depends on vertical accretion of organic and inorganic matter, which vary in their relative abundance across estuarine gradients. We examined the relative contribution of organic and inorganic matter to vertical soil accretion using lead-210 (210Pb) dating of soil cores collected in tidal wetlands spanning a tidal freshwater to brackish gradient across a Chesapeake Bay subestuary. Only 8 out of the 15 subsites had accretion rates higher than relative sea level rise for the area, with the lowest rates of accretion found in oligohaline marshes in the middle of the subestuary. The mass accumulation of organic and inorganic matter was similar and related (R2 = 0.37). However, owing to its lower density, organic matter contributed 1.5–3 times more toward vertical accretion than inorganic matter. Furthermore, water/porespace associated with organic matter accounted for 82%–94% of the total vertical accretion. These findings demonstrate the key role of organic matter in the persistence of coastal wetlands with low mineral sediment supply, particularly mid-estuary oligohaline marshes.

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The potential impacts of sea level rise on the coastal region of New Jersey, USA

Climatic Change ◽

10.1007/s10584-008-9422-0 ◽

2008 ◽

Vol 90 (4) ◽

pp. 475-492 ◽

Cited By ~ 68

Author(s):

Matthew J. P. Cooper ◽

Michael D. Beevers ◽

Michael Oppenheimer

Keyword(s):

New Jersey ◽

Sea Level Rise ◽

Sea Level ◽

Coastal Region

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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

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.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.

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Holocene sea level and climate interactions on wet dune slack evolution in SW Portugal: A model for future scenarios?

The Holocene ◽

10.1177/0959683618804633 ◽

2018 ◽

Vol 29 (1) ◽

pp. 26-44 ◽

Cited By ~ 2

Author(s):

Manel Leira ◽

Maria C Freitas ◽

Tania Ferreira ◽

Anabela Cruces ◽

Simon Connor ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Environmental Changes ◽

Sediment Accumulation ◽

High Energy ◽

Sediment Supply ◽

Dune Slack ◽

Ecological Stability ◽

The Holocene ◽

Climate Interactions

We examine the Holocene environmental changes in a wet dune slack of the Portuguese coast, Poço do Barbarroxa de Baixo. Lithology, organic matter, biological proxies and high-resolution chronology provide estimations of sediment accumulation rates and changes in environmental conditions in relation to sea-level change and climate variability during the Holocene. Results show that the wet dune slack was formed 7.5 cal. ka BP, contemporaneous with the last stages of the rapid sea-level rise. This depositional environment formed under frequent freshwater flooding and water ponding that allowed the development and post-mortem accumulation of abundant plant remains. The wetland evolved into mostly palustrine conditions over the next 2000 years, until a phase of stabilization in relative sea-level rise, when sedimentation rates slowed down to 0.04 mm yr−1, between 5.3 and 2.5 cal. ka BP. Later, about 0.8 cal. ka BP, high-energy events, likely due to enhanced storminess and more frequent onshore winds, caused the collapse of the foredune above the wetlands’ seaward margin. The delicate balance between hydrology (controlled by sea-level rise and climate change), sediment supply and storminess modulates the habitat’s resilience and ecological stability. This underpins the relevance of integrating past records in coastal wet dune slacks management in a scenario of constant adaptation processes.

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Supplemental Material: Detrital signals of coastal erosion and fluvial sediment supply during glacio-eustatic sea-level rise, Southern California, USA

10.1130/geol.s.15138651.v3 ◽

2021 ◽

Author(s):

Glenn Sharman ◽

et al.

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Coastal Erosion ◽

Southern California ◽

Mixture Modeling ◽

Sediment Supply ◽

Analytical Methodology ◽

Fluvial Sediment ◽

Icp Ms ◽

Data Tables

Sample summary, LA-ICP-MS data tables, sources of Cretaceous-Paleogene forearc data, Peninsular Ranges batholith zircon U-Pb ages, mixture modeling results, and U-Pb analytical methodology.

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