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Storm surge is the most serious marine disaster in China, and the inundation characteristics of storm surge are the key indicators of disaster severity. Especially in the context of relative sea level rise (RSLR), it is very important to rapidly and accurately estimate the inundation characteristics of storm surge for the risk assessment and emergency management of storm surge disasters. Taking Taizhou city, Zhejiang Province, as the study area, this paper constructed an RSLR scenario library considering absolute sea level rise, land subsidence and storm surge water increase. The scenario library includes 72 scenarios, consisting of a combination of four absolute sea level rise scenarios, three land subsidence scenarios, three timescales (2030, 2050 and 2100) and two storm surge water increase scenarios. Then, an improved passive inundation method was used to predict and analyze the inundation characteristics of storm surge under each scenario. This improved method combines the advantages of the accurate active inundation method and the rapid passive inundation method, and is suitable for rapid and accurate estimation of the storm surge inundation characteristics, which can meet the needs of a storm surge disaster risk assessment and emergency response. The prediction and analysis results show that a minor RSLR can also cause a large-scale inundation in coastal areas of Taizhou. When the value of RSLR exceeds the critical value (0.6 m), it may significantly increase the expansion of the inundation area of storm surge. At a relative sea level rise of 1.57 m (extreme scenario in 2100), the inland storm surge inundation of low-risk areas may become high-risk areas. Finally, the quantitative measures for preventing storm surge disasters were put forward according to the current situation of the coast in Taizhou. Without considering storm surge and superimposed general surge, the existing 20-year return period standard seawall can effectively protect against storm surge under various scenarios. In the case of maximum water increase, it is expected that effective protection will remain until 2030, but the standard of the seawall defense will need to be improved in 2050 and 2100. [ABSTRACT FROM AUTHOR]

Coastal management in China is confronted with an urgent choice between natural restoration and maintenance of existing seawalls and reclaimed land for economic development. A key criterion for making this decision is the resilience to coastal flooding, which depends on the ability to predict tidal level. Tidal duration asymmetry (TDA) is a key parameter in determination of the arrival and duration of flood tides. This study selected the western inner shelf of the Yellow Sea (WYS) as the study area and investigated the responses of TDA to different shoreline configurations and relative sea level rise. The responses of TDA to shoreline reconstruction yielded spatial variability locally and remotely. In the nearshore area, the responses of TDA to the complex ocean environment mainly originated from the combined functions of reflection, bottom friction, and advection, which controlled the energy transfer from M2 or S2 constituents to their overtides or compound tides. The sensitivity of TDA to coastline typologies was not limited to coastal waters but could stretch over the entire inner shelf. The vulnerability of tidal responses was due to the displacement of the M2 amphidrome of the Kelvin wave on the WYS, which in turn changed tidal energy fluxes over the regime. The relative sea level rise could intensify the feedback of TDA to seawalls and land reclamation.

Storm surge is the most serious marine disaster in China, and the inundation characteristics of storm surge are the key indicators of disaster severity. Especially in the context of relative sea level rise (RSLR), it is very important to rapidly and accurately estimate the inundation characteristics of storm surge for the risk assessment and emergency management of storm surge disasters. Taking Taizhou city, Zhejiang Province, as the study area, this paper constructed an RSLR scenario library considering absolute sea level rise, land subsidence and storm surge water increase. The scenario library includes 72 scenarios, consisting of a combination of four absolute sea level rise scenarios, three land subsidence scenarios, three timescales (2030, 2050 and 2100) and two storm surge water increase scenarios. Then, an improved passive inundation method was used to predict and analyze the inundation characteristics of storm surge under each scenario. This improved method combines the advantages of the accurate active inundation method and the rapid passive inundation method, and is suitable for rapid and accurate estimation of the storm surge inundation characteristics, which can meet the needs of a storm surge disaster risk assessment and emergency response. The prediction and analysis results show that a minor RSLR can also cause a large-scale inundation in coastal areas of Taizhou. When the value of RSLR exceeds the critical value (0.6 m), it may significantly increase the expansion of the inundation area of storm surge. At a relative sea level rise of 1.57 m (extreme scenario in 2100), the inland storm surge inundation of low-risk areas may become high-risk areas. Finally, the quantitative measures for preventing storm surge disasters were put forward according to the current situation of the coast in Taizhou. Without considering storm surge and superimposed general surge, the existing 20-year return period standard seawall can effectively protect against storm surge under various scenarios. In the case of maximum water increase, it is expected that effective protection will remain until 2030, but the standard of the seawall defense will need to be improved in 2050 and 2100.

Increasing sea levels and water temperatures have been detected at several coastal locations worldwide with severe consequences on the communities and ecosystems. Coastal lagoons are particularly vulnerable to such changes due to their low land elevation and limited connections with the open sea. Here the recent and future climatic changes in the Lagoon of Venice (Italy) are investigated using in-situ observations and high-resolution hydrodynamic modeling. Trend analysis was applied to observed time series of meteorological and oceanographic climate essential variables to identify significant long-term changes in mean and extreme values. The mean relative sea level rose at a rate of 4.9 mm per year in Venice due to the combined action of eustacy and subsidence while air and sea temperatures increased on average by 1.8 and 1.1°C in 30 years, respectively. These rates, as well as climate projections, were used following a pseudo-global-warming approach to investigate the near future (up to 2050) evolution of the lagoon's dynamics focusing on sea level and temperature extremes. The lagoon will amplify the temperature changes expected for the Adriatic Sea, especially in the shallow tidal flats where the intensity of the marine heat waves will be more than four times larger than that in the open sea. Moreover, the model allowed us to perform “what-if” scenarios to explore to which extent the flood protection MoSE barriers will modify the lagoon's dynamics. According to the simulations, the number of floods and therefore of the MoSE closure strongly increases with sea level rise. In the most severe scenario, MoSE will have to close for more than 20% of the time in October, November, and December resulting in the reduction of water exchange with the open sea and exacerbation of marine cold spells. Some considerations on the implications of the expected changes on the lagoon's ecology are proposed.

Here we show the SAVEMEDCOASTS-2 web-based geographic information system (webGIS) that supports land planners and decision makers in considering the ongoing impacts of Relative Sea Level Rise (RSLR) when formulating and prioritizing climate-resilient adaptive pathways for the Mediterranean coasts. The webGIS was developed within the framework of the SAVEMEDCOASTS and SAVEMEDCOASTS-2 projects, funded by the European Union, which respond to the need to protect people and assets from natural disasters along the Mediterranean coasts that are vulnerable to the combined effects of Sea Level Rise (SLR) and Vertical Land Movements (VLM). The geospatial data include available or new high-resolution Digital Terrain Models (DTM), bathymetric data, rates of VLM, and multi-temporal coastal flooding scenarios for 2030, 2050, and 2100 with respect to 2021, as a consequence of RSLR. The scenarios are derived from the 5th Assessment Report (AR5) provided by the Intergovernmental Panel on Climate Change (IPCC) and encompass different Representative Concentration Pathways (RCP2.6 and RCP8.5) for climate projections. The webGIS reports RSLR scenarios that incorporate the temporary contribution of both the highest astronomical tides (HAT) and storm surges (SS), which intensify risks to the coastal infrastructure, local community, and environment. [ABSTRACT FROM AUTHOR]

The development of emerging technologies poses some risks while improving urban construction and human life, thus further causing urban safety problems. Tianjin is a coastal city in China, where the coastal sea level keeps increasing, water cycling is changed by the water supply of the South - to - North Water Diversion Project, and the underground space is subject to development and utilization. These factors, coupled with land subsidence, are all critical for the assessment of emerging risks in Tianjin. This study extracted information on the land subsidence of the southern plain in Tianjin and then predicted the retreat of the natural coastline in Tianjin by combining the sea level rise rate. Accordingly, this study predicted the high - risk factors brought by relative sea level rise in Tianjin using a machine learning method (XGBoost) . In addition, this study analyzed the emerging risks caused by the South - to - North Water Diversion Project and the development and utilization of underground space and revealed the response patterns of the water supply and the construction and operation of subways to the urban safety of Tianjin. The study on the emerging risks brought about by the combination of land subsidence and modern human activities will provide a scientific basis for regional disaster prevention and mitigation and improve cities' ability to resist disasters. [ABSTRACT FROM AUTHOR]

High coastal sectors constitute the most widespread coastal environment and, under the present accelerated sea-level rise scenario, are suffering huge impacts in terms of erosion. The aim of this paper is the proposal of a new methodological approach for the assessment of their susceptibility to erosive processes. The method is based on the combination of two matrices, i.e., a matrix considering the main physical elements (essentially morphological and geotechnical characteristics) that determine the proneness to erosion of a specific high coastal sector, and a forcing matrix, which describes the forcing agents affecting the considered sector. Firstly, several variables were selected to construct each one of the two matrices according to existing studies and, in a second step, they were interpolated to obtain the susceptibility matrix (CSIx). The approach was applied to Procida Island and Cilento promontory, both located in southern Italy. Results obtained were validated by comparing them with cliff retreat data obtained by means of aerial photographs and satellite images. The analysis shows that the greater part of the analyzed high coastal sectors belongs to the high-susceptibility class due to the combination of adverse morphological, geotechnical and forcing characteristics. Such sectors can be considered "hotspots" that require an increase in monitoring programs and, at places, urgent protective actions. [ABSTRACT FROM AUTHOR]

Here we show the SAVEMEDCOASTS-2 web-based geographic information system (webGIS) that supports land planners and decision makers in considering the ongoing impacts of Relative Sea Level Rise (RSLR) when formulating and prioritizing climate-resilient adaptive pathways for the Mediterranean coasts. The webGIS was developed within the framework of the SAVEMEDCOASTS and SAVEMEDCOASTS-2 projects, funded by the European Union, which respond to the need to protect people and assets from natural disasters along the Mediterranean coasts that are vulnerable to the combined effects of Sea Level Rise (SLR) and Vertical Land Movements (VLM). The geospatial data include available or new high-resolution Digital Terrain Models (DTM), bathymetric data, rates of VLM, and multi-temporal coastal flooding scenarios for 2030, 2050, and 2100 with respect to 2021, as a consequence of RSLR. The scenarios are derived from the 5th Assessment Report (AR5) provided by the Intergovernmental Panel on Climate Change (IPCC) and encompass different Representative Concentration Pathways (RCP2.6 and RCP8.5) for climate projections. The webGIS reports RSLR scenarios that incorporate the temporary contribution of both the highest astronomical tides (HAT) and storm surges (SS), which intensify risks to the coastal infrastructure, local community, and environment.

A model-based assessment of the response of mean salinities to relative sea level rise (RSLR) in a brackish floodplain region is presented. The study area is located on the Gulf coastal region of Louisiana which is experiencing some of the highest rates of relative sea level rise in the world. A two-dimensional modeling approach is developed, and the local hydrodynamic model is well calibrated for scenario testing purposes. Numerous alternative scenarios of RSLR are evaluated to simulate the salinity response in both the open water and adjacent floodplain areas under a range of wetland roughness and dispersion factors. The analysis reveals key insights on the mean salinity response patterns to RSLR including the sensitivity to deterioration of wetlands and offshore boundary conditions. Also developed are expressions describing the qualitative nonlinear response. A novel partitioning strategy is also employed in the simulation trials to analyze the effect of various accretion deficit scenarios on the nonlinear RSLR-induced salinity response. The analysis shows that the fraction of the floodplain which is able to keep pace with RSLR has an effect an order of magnitude larger than transport parameters associated with marsh deterioration on the RSLR salinity response. Sites exhibiting sustained accretion surpluses over the long term are able to keep pace and would likely contribute to greater overall resilience to future RSLR-induced salinity changes. The robust scenario analysis and findings of this study are widely applicable to the global challenge of managing the effects of RSLR in coastal wetland areas. [ABSTRACT FROM AUTHOR]

The town of Rue was one of the most important coastal harbours of Picardy, Northern France, from the beginning of the 12th century to the end of the 15th century CE. Document sources and ancient maps confirm the existence of this vibrant harbour. Until now, however, no palaeoenvironmental studies have attempted to reconstruct the configuration of the region's coastline during medieval times. Here we employ a geoarchaeological approach to reconstruct the Mid-to Late Holocene shoreline and landscape changes in the Rue area. Our approach includes a geophysical survey (Electric Resistivity Tomography method) and a series of eight sediment cores that reveal the region's chronostratigraphy. Document sources were also used to shed light on the landscape configuration during the Late Middle Ages (ca. 1300 CE). Our coring results, based on sedimentological analyses, are combined with 2D geophysical profiles down to 21.50 m. This reveals, firstly, that a calm marine environment prevailed at the beginning of the 4th millennium BCE, particularly in depressions bordered by Pleistocene coastal spits (foraines). Secondly, from ca. 3500 BCE to ca. 1000 BCE, coastal swamps predominated. Then, thirdly, at around 1000–1250 CE, an estuarine depositional environment prevailed, prior to a final period of land reclamation of the former Maye Estuary from the 13th century CE onwards. These results agree well with recent work on sea level changes along the Atlantic and English Channel coasts of France, where continuous post-glacial sea level rise has been observed. Our study also proposes a location of the medieval harbour of Rue to the west of the town at the upstream boundary of the upper part of the Maye Estuary, near ' Le Moulin de Saint-Jean' , although archaeological evidence of the exact site of this tidal harbour is still lacking. [ABSTRACT FROM AUTHOR]

• During sea-level rise, an alluvial-deltaic system has a critical spatial dimension. • The over-expanded system is subjected to non-deltaic transgression with shrinkage. • Shrinkage can be normalized by autostratigraphic length and time scales. • During shrinkage, the alluvial channels change their intrinsic behavior. • The shrinkage concept can account for some alluvial features on Earth and Mars. The dynamics of downstream alluvial systems undergoing relative sea level (RSL) rise exhibit significant variations depending on spatial size. According to autostratigraphy theory, such systems cannot sustain deltaic sedimentation under a steady RSL rise (rate R slr), and are prone to non-deltaic transgression once their plain area A exceeds the critical limit A crt. During this transgression, A decreases asymptotically toward A crt , while the overall alluvial aggradation rate R agg_overall increases toward R slr. In this study, we investigated the behavior and morphodynamics of an overexpanded system through physical modeling, with a focus on the inherent area scale of the depositional system. In the early stages of non-deltaic transgression (A >> A crt , R agg_overall << R slr), the alluvial channels experience minimal aggradation rate R agg_channel (< R slr), leading to stabilization and inundation. As the transgression progresses, the channels aggrade more rapidly, increasing the likelihood of lateral migration and avulsion. Eventually, a state of morphodynamic equilibrium is reached, characterized by A ∼ A crt , R agg_overall ∼ R slr , and R agg_channel ∼ constant > R slr despite sustained non-deltaic transgression. During this equilibrium stage, the channels undergo rapid aggradation, resulting in complete destabilization with continuous lateral migration and frequent avulsion, forming system-wide subaqueous steps. The implications of overexpansion and autogenic shrinkage in response to RSL rise extend to stratigraphic convergence during RSL cycles and provide insights into Holocene non-deltaic transgression. Moreover, when combined with decelerating RSL rise, this process could have facilitated marine delta development. However, projected accelerated RSL may lead many modern marine deltas to transition into non-deltaic transgressive systems. Additionally, natural alluvial channels may exhibit varying behavior depending on the spatial size of the non-deltaic transgressive system. Furthermore, the autogenic shrinkage model may offer an explanation for the stepped surfaces observed on alluvial fans and deltas on Mars. [ABSTRACT FROM AUTHOR]

Numerous unique flora and fauna inhabit the Lower Florida Keys, including the endangered Florida Key deer, found nowhere else. In this vulnerable habitat of flat islands with low elevation, accelerated sea level rise poses a threat. Predicting the impact of sea level rise on vegetation and wildlife is crucial. This study used 5 Intergovernmental Panel on Climate Change (IPCC) sea level rise scenarios to assess their effects on No Name Key, Florida. The goal was to estimate changes in the Florida Key deer population relative to sea level rise using a lidar-derived elevation data and a vegetation map. The method used 2 cases to model the sea level rise impact. In Case 1, total non-submerged area at current sea level was determined. Using 5 IPCC scenarios, a new total non-submerged land area was estimated, and deer numbers were predicted for each scenario. In Case 2, upward migration of coastal vegetation combined with the coastal squeeze process was modeled. A distinct elevation range for each vegetation type at the current sea level was determined. Vegetation ranges were redistributed based on respective elevation ranges in the sea level rise scenarios. Areas for each vegetation type were recalculated, and Key deer numbers were estimated for each sea level rise scenario. Results under the worst emission scenario showed the following: (1) for case 1, the land area was reduced to 30 % of the current land area, corresponding to having about 27 deer, and (2) for case 2, the land area was reduced to 70 % of the current land area, having about 54 deer on No Name Key. The results indicated reduced non-submerged land area and less upland vegetation, particularly hardwoods/hammocks, by the year 2100. As less land area is available, a decline in Key deer population is expected as sea levels rise. Since Key deer favor upland vegetation, habitat affected by sea level rise will likely support a smaller deer population. The findings emphasize the need for precise, timely predictions of sea level rise impacts and long-term conservation strategies. Specifically designed measures are required to protect and maintain endangered wildlife, such as the Florida Key deer, residing on these vulnerable islands. • Lidar terrain elevation and habitat cover classes predict change in Key deer habitat. • Area change was used to predict deer population in sea level rise affected habitat. • Vegetation's upward migration and coastal squeeze were included in habitat modeling. • Timely wildlife sea level rise impact assessments ensure crucial response strategies. [ABSTRACT FROM AUTHOR]

Low-lying coastal areas are threatened worldwide by compound flooding effects, including sea-level rise (SLR), frequent tropical cyclones (TCs), and accelerated land subsidence (LS). Compound flooding results in a negative effect, creating challenges for decision-making and coastal management for sustainable urban development. To comprehend the precise consequences and the combined effect of LS and SLR on coastal cities and to inform management scientifically, we initially chose historical TCs (TC6311 and TC1415) that resulted in exceptionally high surges and significant losses as reference scenarios for simulating potential compound events. We then utilized a hydrodynamic model, which combines TCs, LS, and SLR, to simulate the combined impact of flood hazards. Our findings indicated that the highest subsidence rate exceeds −20 mm/yr, the cumulative subsidence reaches −119.09 mm and 68.44% of the land is experiencing subsidence from 2015 to 2021. When comparing flood scenarios with and without the influence of SLR, the most severely affected by LS is projected to become submerged and completely inundated by 2100. We found that the combined impact of SLR and LS significantly amplified flood inundation and SLR is the primary amplification factor of flooding, projected to account for 46.2% by 2100. The framework established in this study facilitates the quantitative assessment of the interactions among multi-driver factors of compound flooding, thereby serving as a supplementary and guiding tool for future risk management. • Propose a framework combining multi-driver factors and hydrodynamics to quantitatively assess the compound flood disaster in coastal cities. • Combined impacts of sea level rise, land subsidence, and tropical cyclones significantly amplify flood inundation. • Regions with higher LS are more vulnerable to flooding driven by sea level rise and land subsidence. • The combined impact of SLR and LS on compound flooding during TCs was not a simple linear addition of individual factors. • Provide new insights into integrating multiple drivers of compound flooding into coastal management and policy. [ABSTRACT FROM AUTHOR]

Coastal flood impact assessments are important tools for risk management and are performed by combining the hazard component with the vulnerability of exposed assets, to quantify consequences (or impacts) in terms of relative or absolute (e.g. financial) damage. The process generates uncertainties that should be taken into account for the correct representation of the consequences of floods. This study presents a coastal flood impact application at the spatial level of the Stavanger municipality (Norway), based on a multi-damage model approach able to represent impacts, and their overall uncertainty. Hazard modelling was performed using the LISFLOOD-FP code, taking into account historical extreme water level events (1988–2017) and relative sea level rise scenarios. Direct impacts were calculated in the form of relative and financial damage for different building categories, using flood damage curves. The results showed that the expected impacts are fewer than 50 flooded receptors and less than €1 million in damage in the current sea level scenario. The impacts could double by the end of the century, considering the most optimistic relative sea level scenario. The results were discussed considering the limitations of the approach for both hazard and impact modelling, that will be improved in future implementations. The outcome of this study may be useful for cost–benefit analyses of mitigation actions and local-scale plans for adaptation.

The article substantiates the conclusion about the tectonic nature of the last global transgression of the World Ocean. It is based on the results of marine studies in which complete sections of transgression sediments were obtained that were separated from their substrate by the diachronous boundary of a stratigraphic uncomformity or those beginning with littoral facies. The radiocarbon dating of such sections at different levels made it possible to calculate the average rate of relative sea level rise by plotting the radiocarbon age of sediments against depth from the seafloor surface. This was constructed based on three reference areas: the underwater slope of the island of Barbados, the North Sea shelf, and the Barents Sea shelf. It was revealed that the average rates of relative sea level rise at different points in the same water area sometimes differ by an order of magnitude, which is incompatible with the eustatic nature of transgression. The maximum transgression amplitudes in the Barents and North seas are several times higher than those permissible for glacio-eustasy. It is assumed that tectonic subsidence of the area due to the planetary nature of the last marine transgression overlapped its immersion, associated with the incomplete formation of the youngest oceanic depressions of the planet located north of the submarine Greenland–Scotland Ridge. [ABSTRACT FROM AUTHOR]

The coastal areas of the central Mediterranean Sea are sensitive to climate change and the consequent relative sea level rise. Both phenomena may affect densely urbanized and populated areas, causing severe damages. Our maps show the land-marine flooding projections as effects of the expected relative sea level rise for four Italian coastal plains using (i) IPCC AR5 estimations, based on the IPCC RCP 8.5 emission scenarios and (ii) the Rahmstorf 2007 model. Isostatic and tectonic data were added to the global projections to estimate the relative sea changes expected along the coastline by 2100, as well as sea-flooding. The northern Adriatic map shows the study area, extending for about 5500 km2, and is presented at a scale of 1:300,000 with two inset maps at a scale of 1:150,000. The Oristano coastal plain is about 125 km2; the map scale is at 1:60,000 with an inset map scale at 1:33,000. The Cagliari coastal study area extends for 61 km2; the map scale is at 1:60,000 with two inset maps at 1:30,000. The Taranto area extends for 4.2 km2 and is represented at a scale map of 1:30,000, while the three inset maps are at a scale of 1:10,000.

Ecogeomorphic characteristics of tidal marshes are strongly related to their elevation with respect to the mean sea level. Predicting the long‐term evolution and resilience of such ecosystems in times of rapid natural and anthropogenic climate changes is of critical importance. The notion that the tidal marsh elevation is the result of feedbacks between vegetation dynamics, sediment fluxes, natural consolidation, and sea‐level changes is widely recognized. However, the interaction of these processes has been poorly investigated until now. This contribution aims at presenting a novel numerical model to simulate the above‐surface and subsurface coupled dynamics of a tidal landscape in a 2‐D‐framework, with the relative sea‐level rise (RSLR) acting as an external stressor. A biomorphological model is used to compute deposition fluxes, which depends on topography and availability of organic/inorganic sediments. The outcome is used as forcing term in a physically based geomechanical model to simulate the consolidation of the marsh body that, in turn, influences sediment fluxes by acting on the platform elevation. The results demonstrate how compaction of the marsh body can crucially affect the resilience of tidal landforms to RSLR accelerations. With normal sediment concentration in coastal waters (10

The subsidence of the Ganges‐Brahmaputra‐Meghna Delta (GBMD) drastically increases the adverse impacts of coastal flooding and exacerbates the vulnerability of populations from ongoing rapid sea level rise. We focus here on estimating the present‐day subsidence rates induced by the loading of sediments continuously deposited within the GBMD over the past 11,000 years. By constructing a realistic GBMD 3‐D numerical model with laterally variable mantle and lithospheric structure, we demonstrate for the first time that the presence of the strong Indian Craton and the weakened Indo‐Burma margin results in significant amplification of subsidence driven by sediment loading in the eastern part of the delta, where the population density is the highest (>1,000 habitants per km2). Although uncertainties remain regarding the amplitude of subsidence, the rate estimates (2–3 mm/year) are found to be comparable to the present‐day global mean sea level rise. Plain Language Summary: Using 3‐D numerical models, we show that the deformation of the Earth surface due to the weight of sediments deposited in the Ganges‐Brahmaputra‐Meghna Delta (GBMD) is probably larger than previously found and induce significant land vertical downward motions in the eastern part of the delta. This process is intimately linked to the complex geological setting of the GBMD (Indian Craton, tectonic plate boundaries), which enhances vertical velocities toward the east. The maximum velocities are found to be located in the region where the population density is the highest. They are of the same order as the rates of present‐day global mean sea level rise. Key Points: In the Ganges‐Brahmaputra‐Meghna Delta, the Indian Craton, and the Indo‐Burman subduction zone enhance the subsidence due to sediment loading toward the eastThe subsidence rate estimates (2–3 mm/year) are comparable to the present‐day global mean sea level riseSubsidence rates are maximum in the most populated area of the delta [ABSTRACT FROM AUTHOR]

The major cause of the Hawaiian Islands coastal erosion is shown to be not global warming, but the sinking of the volcanic islands. The geologic “circle-of-life” beyond the Hawaiian hot spot is the true explanation of the beach erosion. The sea levels are slow rising and not accelerating worldwide as well as in the United States. In the specific of the Hawaii Islands, they have been decelerating over the last 3 decades because of the phasing of the multi-decadal oscillations for this area of the Pacific. There is therefore no evidence coastal erosion will double in the Hawaii by 2050 because of global warming.

Abstract The Sacramento-San Joaquin Delta, like other heavily engineered deltas throughout the world, has undergone substantial subsidence since the late 1800s when the natural estuary was leveed to form islands. Today, islands within the Delta have subsided to the point where most lie below mean sea level. Long-term sustainability of the Delta requires reversal of subsidence, but spatially comprehensive maps of subsidence have not been available to inform and monitor remediation. Reported here is the first spatially dense map of recent subsidence rates across the Delta, based on synthetic aperture radar interferometry and constrained by GNSS observations. The analysis uses a temporally dense and spatially overlapping set of data acquired by the Uninhabited Aerial Vehicle SAR (UAVSAR) sensor in 2009–2015. On average, the Delta is subsiding by 9.2 ± 4.4 mm/yr with high variability even at the sub-island scale, including peak subsidence of 160 ± 4.4 mm/yr occurring just inland of the levee of the westernmost island and average subsidence of 11 mm/yr along the planned path of water conveyance tunnels through the Delta. The results are compared to local sea level rise (SLR), measured at a tidal gauge in San Francisco Bay, to show that subsidence is currently the dominant contributor to local relative sea level rise (RSLR) by nearly a factor of five. Based on recently measured and modeled acceleration of SLR, subsidence in the Delta is likely to dominate RSLR until the middle of the 21th century. Highlights • Sacramento Delta levees protect essential land and water resources of California. • Subsidence of the Sacramento-San Joaquin Delta mapped by combining InSAR and GNSS • UAVSAR observations show an average subsidence rate across the Delta of 9.2 + −± 4 mm/yr. • Subsidence shows high spatial variability, with high rates on and near some levees. • In much of the Delta, subsidence will dominate Relative Sea-Level Rise at least up to 2050. [ABSTRACT FROM AUTHOR]

This study details the chronology and the human consequences of early- to mid-Holocene sea level rise and the related marine transgression and regression along the east coast of China. We use archaeological and environmental data to show that there was a significant marine transgressive event that began before 9000 cal. BP. This event reached its maximum extent inland and had the greatest impact on the Jiangsu region between 9000 and 8000 cal. BP. Because of this transgression, most of the low-lying parts of modern Jiangsu Province were either covered by seawater or were converted to a wetland environment that was unsuitable for long-term human settlements until ca. 7000 cal. BP. Between 7000 and 6000 cal. BP, the sea retreated and new lands became available for colonization. Humans rapidly moved into the newly emerged lands, which were ecologically rich with diverse and abundant plants, animals, fish, and shellfish. Evidence that human settlement were earliest in the northwest and generally expanded south and east. The Taihu Plain was rapidly occupied, but because of variations in topography, hydrology, and sea level changes, the Lixiahe Plain remained a coastal lagoon until 6000–5500 cal. BP. [ABSTRACT FROM AUTHOR]

Globally, episodic coastal flooding is expected to have increasingly severe impacts on agriculture in low-lying coastal areas, as climate change continues to cause relative sea level rise (RSLR). This study analyses dairy farm exposure and impacts from extreme sea levels (ESL) and RSLR in Aotearoa-New Zealand (A-NZ). Spatio-temporal modelling is undertaken using: 1) a dairy production land layer; 2) a static coastal inundation model from 10, 100, 200 and 500-year annual recurrence interval (ARI) ESL events at 0–2 m RSLR (0.5 m increments); and 3) an Impact State (IS) scheme relating percentage of farmland inundated and depth of flooding at milking shed locations to categorise the severity of damage. Through this analysis we highlight the increasing exposure of the dairy industry to coastal flooding, with 472 farms potentially impacted (at or greater than IS 1) by a 10-year ARI event and 1276 farms exposed to a 500-year ARI event at current sea levels, rising to 1276 (10-year ARI) and 1344 farms (500-year ARI) with 2 m RSLR. RSLR is identified as the factor driving this increase in exposure and severity of impacts to dairying, with the increase in the number of farms impacted in a 500-year compared to 10-year event only 5 % greater when considered with 1 m of RSLR, compared to 37 % greater at 0 m RSLR. This has significant implications for A-NZ where the dairy industry is of high economic and social importance, demonstrating the need for industry targeted climate change adaptation and disaster risk reduction measures. [Display omitted] • This study quantifies exposure and impacts to dairy farms from extreme sea level events and relative sea level rise. • The number of farms impacted by a 500 versus a 10-year ESL is only 5% greater with 1m of RSLR and 37% greater at 0m RSLR. • This shows that the driving force behind increasing exposure to coastal inundation is RSLR not event intensity or frequency.. • We expect severe impacts to many farms that were previously only experienced during infrequent ESL events to occur regularly. [ABSTRACT FROM AUTHOR]

Chiayi County is located in the largest alluvial plain of Taiwan with extensive aquaculture and rice farming sustained by water extracted from groundwater wells. Chiayi is a typical aquaculture area affected by land subsidence, yet such lands worldwide combine to provide nearly 90% of global aquaculture products, greatly reducing oceanic overfishing problems. This study uses precision leveling, multi-layer compaction monitoring well (MLCW) and spaceborne SAR interferometry (InSAR) to examine the cause and effect of land subsidence in Chiayi associated with groundwater extractions and changes. Heights at benchmarks in a leveling network are measured annually and soil compactions at 24-26 layers up to 300-m depths at 7 MLCWs are collected at one-month intervals. Over 2007-2011, 15 ALOS/PALSAR images are processed by the method of TCPInSAR to produce subsidence rates. All sensors show that land subsidence occur in most parts of Chiayi, with rates reaching 4.5 cm/year around its coast, a result of groundwater pumping from shallow to deep aquifers. MLCWs detect mm-accuracy seasonal soil compactions coinciding with groundwater level fluctuations and causing dynamic compactions. Compactions near Taiwan High Speed Rail may reduce the strength of the rail's supporting columns to degrade its safety. The SAR images yield subsidence rates consistent with those from leveling and compaction wells after corrections for systematic errors by the leveling result. Subsidence in Chiayi's coastal area leads to relative sea level rises at rates up to 15 times larger than the global eustatic sea level rising rate, a risk typical for world's aquaculture-rich regions. At the fish pond-covered Budai Township, InSAR identifies subsidence spots not detected by leveling, providing crucial geo-information for a sustainable land management for aquaculture industry. [ABSTRACT FROM AUTHOR]

In this study, 364 Landsat satellite images were utilized to study the spatial and temporal shoreline changes of the southern Yellow River Delta in 1976–2016, and a new method revised and improved after Zhang et al. (2016) was proposed. By employing that method, the calculated sea levels calculated from simulated tidal heights and instantaneous shoreline positions rather than simulated tidal heights were used to correct fluctuations in instantaneous shoreline positions caused by tidal height and seasonal sea level changes and other random sea level fluctuations. When calculating the shoreline erosion rates and beach slopes, a statistical analysis of a large number of corrected shoreline positions was used to reduce the influence of random errors that were mainly caused by waves and other casual factors. The shoreline erosion rates and beach slopes presented in this paper are therefore more precise and reliable than those derived in previous studies, which only used two satellite images. The results of this study show that the shoreline of the southern Yellow River Delta primarily experienced gradual erosion during 1976–2016, with an average erosion rate of 26.9 m/year. The average shoreline erosion rate increased from 24.9 m/year in 1976–1996 to 34.9 m/year in 1996–2016—an increase of 40%—probably due to the reduction in sediment discharge and shifting northward course of the Yellow River after 1996. The shoreline erosion rate of the central coast decreased from 50.2 m/year in 1976–1996 to 27.1 m/year in 1996–2016—a decrease of 46%—probably due to the protection offered by coastal hard structures. The average shoreline erosion rate caused by relative sea level rise was 8.5 m/year or 32% of the total average shoreline erosion rate. Relative sea level rise plays an important role in the erosion of the southern Yellow River Delta due to its flat beach. The beach slope of the southern Yellow River Delta was flat and stable in 1976–2016, and the average slope over most of the beach was 0.043%. [ABSTRACT FROM AUTHOR]

Interdisciplinary studies of the last years highlight that the Italian coasts are significantly subject to retreat and to inundation by sea ingression due to natural and anthropic causes. In this study, the effects of future relative sea level have been evaluated for the Volturno River Plain, one of the widest coastal plain in southern Italy. The plain is characterized by high economical and ecological value, for the presence of farm activities, tourist structures and wetland protected zones. The study area is potentially prone to coastal flooding due to its very low topography and because it is affected by a severe subsidence, which emphasize the local effect of sea level rise due to the ongoing climate changes. In accordance with the guidelines of the MEDFLOOD project, the areas prone to inundation in the years 2065 and 2100 have been evaluated by comparing the future topographical information and expected relative sea level scenarios. The local Vertical Ground Displacements have been derived by PS-InSAR processing data whilst the mean values of the scenarios RCP 2.6 and RCP 8.5 provided by the IPCC (2014) have been used as future sea level projections in 2065 and 2100. The PS-InSar data elaboration shows that the area affected by subsidence corresponds to 35% of the Volturno plain and that the annual rate of the phenomenon ranges between −1 and −25 mm/yr. The inundation analysis, based on the classification of the areas in four hazard classes, indicates that in 2065 the zones located below the sea level will increase approximately of 50% respect to the present conditions, while between 2065 and 2100 the increase can be at least of 60% (IPCC, RCP 8.5 scenarios). Considering the socio-economical and ecological exposure, evaluated following the EUROSION project guidelines, the coastal flooding risk maps have been produced. Almost 8.2 km 2 and 14.4 km 2 of the investigated area has to be considered subject to very high marine inundation risk in 2065 and 2100, respectively. [ABSTRACT FROM AUTHOR]

Coastal and estuarine systems worldwide are under threat from global climate change, with potential consequences including an increase in salinities and incursion of saltwater into areas currently subject to tidal and non-tidal freshwater regimes. It is commonly assumed that climate-driven increases in estuarine salinities and saline incursion will be directly reflected in an upstream shift in species distributions and patterns of community composition based on salinity tolerance. This study examined the responses of benthos to medium-term salinity changes in two macrotidal river-estuary systems in SE England to test whether these responses may be representative of climate-induced salinity changes over the long-term. The study reinforced the effect of salinity, related to tidal incursion, as the primary environmental driver of benthic species distribution and community composition. Salinity, however, acted within a hierarchy of factors followed by substratum type, with biotic competition and predator-prey relationships superimposed on these. The assumption that increasing salinities will be directly reflected in a shift in species distributions and patterns of community composition upstream over the long-term was shown to be over simplistic and not representative of a complex and highly variable system. Relative Sea Level Rise (RSLR) projections were predicted to increase estuarine salinities and saline incursion in the study estuaries, which together with projected reductions in river flow will have important consequences for estuarine structure and function, particularly in tidal limnetic zones, despite estuarine communities being pre-adapted to cope with fluctuating salinities. The study identified, however, that limnic-derived fauna inhabiting these zones may demonstrate greater tolerance to salinity change than is currently recognised, and may persist where salinity increases are gradual and zones unbounded. [ABSTRACT FROM AUTHOR]

The coastal areas of the central Mediterranean Sea are sensitive to climate change and the consequent relative sea level rise. Both phenomena may affect densely urbanized and populated areas, causing severe damages. Our maps show the land-marine flooding projections as effects of the expected relative sea level rise for four Italian coastal plains using (i) IPCC AR5 estimations, based on the IPCC RCP 8.5 emission scenarios and (ii) the Rahmstorf 2007 model. Isostatic and tectonic data were added to the global projections to estimate the relative sea changes expected along the coastline by 2100, as well as sea-flooding. The northern Adriatic map shows the study area, extending for about 5500 km2, and is presented at a scale of 1:300,000 with two inset maps at a scale of 1:150,000. The Oristano coastal plain is about 125 km2; the map scale is at 1:60,000 with an inset map scale at 1:33,000. The Cagliari coastal study area extends for 61 km2; the map scale is at 1:60,000 with two inset maps at 1:30,000. The Taranto area extends for 4.2 km2and is represented at a scale map of 1:30,000, while the three inset maps are at a scale of 1:10,000. [ABSTRACT FROM PUBLISHER]

Through index-based method, the coastal economic vulnerability of Bohai Rim in China to the hypothetical local scenario of 1-m relative sea level rise by the end of twenty-first century was assessed (note that 1-m global sea level rise throughout the twenty-first century is highly improbable). Both physical and socioeconomic variables were considered, and the comparison between physical vulnerability and economic vulnerability was conducted to identify effects of socioeconomic variables on coastal susceptibility to sea level rise. The assessment was carried out at shoreline segments scale as well as at county-level scale, and the results were as follows: The combination of geomorphology and terrain plays the determinant role, since the gently sloped coasts with softer substances are always both physical and economic susceptible to the projected inundation scenario; potential displaced population and GDP loss have more influence on economic vulnerability than reclamation density in that the most intensively reclaimed areas are not always high vulnerable, while the areas that may suffer from the largest potential displaced population and GDP loss are always high vulnerable; the method employed in this study is sensitive in identifying the relative difference in economic vulnerability; moreover, it is capable of handling the issues caused by mutual offset effects between land-controlling impacts and marine-controlling impacts. The insights offered by this study could inform the coastal managers in optimizing allocation of limited resources and, consequentially, assist them to sequence policy, planning and management choices efficiently and effectively to adapt to the sea level rise. [ABSTRACT FROM AUTHOR]

Recent works (Evelpidou et al., 2012) suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century. In order to assess this hypothesis, we measured modern tidal notches in several of sites along the Mediterranean coasts. We report observations on tidal notches cut along carbonate coasts from 73 sites from Italy, France, Croatia, Montenegro, Greece, Malta and Spain, plus additional observations carried outside the Mediterranean. At each site, we measured notch width and depth, and we described the characteristics of the biological rim at the base of the notch. We correlated these parameters with wave energy, tide gauge datasets and rock lithology. Our results suggest that, considering ‘the development of tidal notches the consequence of midlittoral bioerosion’ (as done in Evelpidou et al., 2012) is a simplification that can lead to misleading results, such as stating that notches are disappearing. Important roles in notch formation can be also played by wave action, rate of karst dissolution, salt weathering and wetting and drying cycles. Of course notch formation can be augmented and favoured also by bioerosion which can, in particular cases, be the main process of notch formation and development. Our dataset shows that notches are carved by an ensemble rather than by a single process, both today and in the past, and that it is difficult, if not impossible, to disentangle them and establish which one is prevailing. We therefore show that tidal notches are still forming, challenging the hypothesis that sea level rise has drowned them. [ABSTRACT FROM AUTHOR]

This paper illustrates an index-based coastal risk assessment that was performed on a micro-tidal alluvial plain taking into account the relative sea level rise (RSLR) for the evaluation of coastal vulnerability and exposure. This process took into account both the inundation of inshore land and the beach retreat due to storm surge, calculated on the basis of geomorphological data (bathymetry, sedimentology and beach width) and wave climate. The evaluation process was conceived with reference to a low and high hazard, associated with a wave storm with 1 year and 50 years return period. For the latter case, the response to RSLR was calculated taking into account both isostatic response and ice cap melting due to global warming, while the vertical land movement was assessed taking into account the different its rates in the northern and southern coastal area. The exposure and the damage of the coastal assets were evaluated with a simplified conceptual framework, which uses land cover data and a statistical population dataset. The risk assessment procedure was applied to Sele coastal plain, which involves numerous properties and important infrastructures, and is strongly susceptible to marine inundations. A sensitivity analysis of the vulnerability and the risk relative to different hazards and to RSLR was performed. Moreover, the final risk assessment classification was validated with a conceptual framework based on the observed damage ranking related to the tested coastal area. The obtained results showed that the northern high density urban areas were characterized by the highest risk, followed by some central areas with strong localized erosive focus. On the contrary, the southern zones, with wider beaches and almost intact dunes, were characterized by the lowest risk level. The results of this study were used for the development of a coastal protection project which, in fact, provided a different scheme for the coastline northwards and southwards of the Sele river mouth, according to the different risk ranking established. [ABSTRACT FROM AUTHOR]

This study provides guidelines for strategic management in industrial oil plants linked to uncertainties of climate change through the development of integrated planning methodology with focus on coastal flooding events caused by relative sea level rise (RSLR). The research site is in Redonda Island, located in Guanabara Bay, Rio de Janeiro City, Brazil, and since 1960, it constitutes an industrial oil plant facility. The region suffers interaction with storms and meteorological tides from extratropical cyclones over the South Atlantic Ocean, being vulnerable to risks of disasters, floods, and coastal erosion. A Program on Vulnerability and Adaptation Assessments to Relative Sea Level Rise ('Programa de Avaliação e Adaptação às Vulnerabilidades de Elevação do Nível Relativo do Mar-PAAVENRM') was developed to avoid compromising the regional and local development in the industrial system of the island, which is an ad hoc instrument designed to anticipate and reduce risks, damages, and losses by occurrence of extreme climatic events in coastal areas prone to flooding caused by RSLR. Results from computer simulation modeling indicate 37 prospective qualitative scenarios that consolidate the conditions of future climate vulnerability of the plant, starting from United Nations Intergovernmental Panel on Climate Change (IPCC) information for RSLR up to 2100. Three quantitative forecasting scenarios were simulated, under boundary conditions preset for different altimetric ranges subject to submersion, based upon ordinary and extraordinary tides measured in the area in relation to RSLR, which allowed the evaluation of the industrial infrastructure at risk. Furthermore, three thematic maps were elaborated for the planning of specific coastal protection interventions. Percentages of physical damage and property losses were estimated. The importance of applying guidelines for medium and long-term corporate strategy management, integrating the risk of flooding, the rigging of civil defense systems, meteorology, and of the plans, programs, and existing systems and others to be developed is highlighted. From this perspective, the proposed scenarios help to identify the most relevant alternatives for mitigation and adaptation under technical criteria for decision making in the study area. [ABSTRACT FROM AUTHOR]

Based on critical analysis of stratigraphic succesions in the Proterozoic intracratonic basins, geochronological data and possible connections or disconnections with adjacent fold belts and craton margin mobile belts, an overview of the Proterozoic evolution of the Eastern Dharwar and Bastar cratons in India is presented. The Chattisgarh and Cuddapah basins in these cratons with Archean nuclei host sedimentary successions ranging in age from the Paleoproterozoic to the Ediacaran period, and representing several silicilastic and carbonate cycles. The Proterozoic successions of the Pranhita-Godavari valley (PGV) basin along the Dharwar-Bastar join, record multiple rifting since late Neoarchean suturing of the two cratons. We postulate a first order stratigraphic correlation across the cratons and their join and discuss how major sea level fluctuations coupled with regional tectonic events shaped the development of unconformity bound successions, adjoining fold belts and the mobile belts with supposed global tectonic connections. The oldest Paleoproterozoic intracratonic sedimentation is preserved in the Cuddapah and PGV basins, while sedimentation in the Bastar craton is largely Mesoproterozoic. The fluviodeltaic to shallow marine Neoproterozoic sedimentation followed emplacement of end-Mesoproterozoic kimberlites and lamproites indicating thermal rejuvenation of the Indian continental crust. The allochthonus Nallamalai fold belt in eastern Cuddapah basin and the early Mesoproterozoic fold belt in PGV basin point to craton margin crustal convergences which punctuated the Paleoproterozoic sedimentation. Widespread development of carbonate bearing sequences in the Mesoproterozoic to Neoproterozoic successions point to peneplanation of the cratons and stable platformal sedimentation. The Neoproterozoic sedimentation was terminated following the docking of the Eastern Ghats belt to the eastern margin of the Dharwar-Bastar ensemble and possible final tectonic hiccups in the Central Indian Tectonic zone bordering the Bastar craton. The available data and their analysis rule out any foreland basin type connection between the Eastern Ghats belt and cratonic sedimentation in Bastar and Eastern Dharwar. [ABSTRACT FROM AUTHOR]

As an island nation with some 85% of the population residing within 50 km of the coast, Australia faces significant threats into the future from sea level rise. Further, with over 710,000 addresses within 3 km of the coast and below 6-m elevation, the implication of a projected global rise in mean sea level of up to 100 cm over the 21st century will have profound economic, social, environmental, and planning consequences. In this context, it is becoming increasingly important to monitor trends emerging from local (regional) records to augment global average measurements and future projections. The Australasian region has four very long, continuous tide gauge records, at Fremantle (1897), Auckland (1903), Fort Denison (1914), and Newcastle (1925), which are invaluable for considering whether there is evidence that the rise in mean sea level is accelerating over the longer term at these locations in line with various global average sea level time-series reconstructions. These long records have been converted to relative 20-year moving average water level time series and fitted to second-order polynomial functions to consider trends of acceleration in mean sea level over time. The analysis reveals a consistent trend of weak deceleration at each of these gauge sites throughout Australasia over the period from 1940 to 2000. Short period trends of acceleration in mean sea level after 1990 are evident at each site, although these are not abnormal or higher than other short-term rates measured throughout the historical record. [ABSTRACT FROM AUTHOR]

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The Northern Adriatic Coastland, between the cities of Monfalcone and Cattolica, is characterized by locations of great tourist interest, such as the Venice Lagoon and the Romagna Riviera, and areas with a very precarious environmental setting, such as the Valli di Comacchio and the Po River Delta. Therefore, the coastal management and the design of new defence works of the littoral have to be made with the utmost care, possibly with the aid of numerical predictions of the coastal morphodynamics and the flood risk analysis of the lowland involved. In the study area, land may subside due to sediment natural compaction and subsurface fluid (water and gas) withdrawal. At the same time, littoral transport of solid material can contribute appreciably to change the shore morphology. Mean sea level may rise permanently due to global climate change (eustatism) and occasionally due to tides and intensive storm events. The predictions of each individual process is obtained using various ad hoc mathematical models and the outcome of the numerical simulations are managed with a GIS (geographical information system). Coastline evolution until the year 2100 is investigated and risk factor maps of the low-lying coastal areas are generated which account for the hazard of the expected event, and the land economic value and vulnerability. [Copyright &y& Elsevier]

The State of Louisiana is leading an integrated wetland restoration and flood risk reduction program in the Mississippi River Delta. East of New Orleans, Biloxi Marsh, a ~1700 km2 peninsula jutting 60 km north toward the State of Mississippi is one of few Delta wetland tracts well positioned to dissipate hurricane surge and waves threatening the city's newly rebuilt hurricane flood defenses. Both its location on the eastern margin of the Delta, and its genesis as the geologic core of the shallow water St. Bernard/Terre aux Boeuf sub-delta, which was the primary Mississippi outlet for almost 2000 years, make Biloxi Marsh attractive for restoration, now that the Mississippi River Gulf Outlet deep-draft ship channel has been dammed, and 50 years of impacts from construction and operation have abated. Now, the cascade of ecosystem damage it caused can be reversed or offset by restoration projects that leverage natural recovery and increased access to suspended sediment from the Mississippi River. Biloxi Marsh is (1) geologically stable, (2) benefiting from increased input of river sediment, and (3) could be restored to sustainability earlier and for a longer period than most of the rest of the submerging Mississippi Delta. The focus of this review is on the Biloxi Marsh, but it also provides a template for regional studies, including analysis of 2D and 3D seismic and other energy industry data to explore why existing marshes that look similar on the ground or from the air may respond to restoration measures with different levels of success. Properties of inherent durability and resilience can be exploited in restoration project selection, sequencing and expenditure. Issues encountered and investigative methods applied in the Biloxi Marsh are likely to resonate across initiatives now contemplated to sustain valuable river deltas worldwide. [ABSTRACT FROM AUTHOR]