Coastal flooding protection will change salt-marsh sedimentation dynamics

2021 ◽  
Author(s):  
Davide Tognin ◽  
Andrea D'Alpaos ◽  
Marco Marani ◽  
Luca Carniello
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Sedimentation Rate ◽  
Urban Areas ◽  
Storm Surges ◽  
Venice Lagoon ◽  
Water Levels ◽  
Sedimentation Dynamics

<p>Coastal wetlands lie at the interface between submerged and emerged environments and therefore represent unique yet delicate ecosystems. Their existence, resulting from complex interactions between hydrodynamics and sediment dynamics, is challenged by increasing rates of sea-level rise, lowered fluvial sediment input as well as an increasing anthropogenic pressure. The future survival of these peculiar morphologies is becoming even more complicated, because of the construction and planning of coastal defence structures designed to protect urban areas from flooding. Important examples are the flood protection systems built to protect New Orleans (USA), the river Scheldt Estuary (The Netherlands) and Venice (Italy). In this context, understanding the physical processes on which coastal marshes are grounded and how engineering measures can alter them is of extreme importance in order to plan conservation interventions.</p><p>To understand marsh sedimentation dynamics in flood-regulated environments, we investigated through field observations and modelling the effect of the storm-surge barrier designed to protect the city of Venice, the so-called Mo.S.E. system, which has in fact become operational since October 2020.</p><p>Sedimentation measurements in different salt marshes of the Venice lagoon carried out in the period October 2018-October 2020 show that more than 70% of yearly sedimentation accumulates during storm-surge conditions, despite their short duration. Moreover, the sedimentation rate displays a highly non-linear increase with marsh inundation intensity, due to the interplay between higher water levels and greater suspended sediment concentration. Barrier operations during storm surges to avoid flooding of urban areas will reduce water levels and marsh inundation. Therefore, we computed sedimentation in a flood-regulated scenario for the same observation period, using the relation we obtained between tidal forcing and sedimentation rate. Our results show that some occasional closures during intense storm surges (70 hours/year on average) suffice to reduce the yearly sedimentation of the same order of magnitude of the relative sea-level rise rate experienced by the Venice lagoon during the last century (2.5 mm/y).</p><p>We conclude that storm-surge barrier operations can dangerously reduce salt-marsh vertical accretion rate, thus challenging wetland survival in face of increasing sea-level rise.</p>

Geospatial Risk Assessment of Marine Terminal Infrastructure to Storm Surge Inundation and Sea Level Rise

2018 ◽  
Vol 2672 (11) ◽  
pp. 19-29 ◽  
Author(s):  
George M. McLeod ◽  
Thomas R. Allen ◽  
Joshua G. Behr
Keyword(s):  
Risk Assessment ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Storm Surges ◽  
Risk Tolerance ◽  
Water Levels ◽  
Rapid Screening ◽  
Tidal Flooding ◽  
The Future

Planning resiliency and sustainability of port operations and critical infrastructure requires risk assessment of storm surge exposure and potential sea level rise. An approach for rapid, screening-level assessment is developed to estimate the current and future risk of exposure to severe storm surges posed to marine terminal facilities in Norfolk, Virginia. The approach estimates the vertical elevation of local mean sea level fifty years into the future and attendant increases in potential storm surge heights. Inundation models are designed for baseline water levels and storm surges for category 1–3 hurricanes across five precautionary future sea level rise scenarios. In addition, tidal flooding poses an emerging threat because sea level rise will also force tides to higher elevations, suggesting that today’s extreme high tides may be the future mean high tide and today’s “nuisance” tidal flooding may in the future recur with chronic regularity. Potential tidal flooding levels are also modeled for each sea level scenario. This approach allows a port to assess relative risk tolerance across the range from lesser to more severe flooding events. Maps and tabular information in linked scenarios are used to summarize the extent, pattern, and depth of potential flooding. The methodology and data developed in this study may be applied to inform the timing and placement of planned assets and can be leveraged in the broader pursuit of optimization in support of long-term master planning at marine terminals.

Integrated extreme sea level events in the Mediterranean coast of Spain

2020 ◽  
Author(s):  
Andrea Lira Loarca ◽  
Manuel Cobos ◽  
Agustín Millares ◽  
Giovanni Besio ◽  
Asunción Baquerizo
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Temporal Variability ◽  
Climate Change Scenario ◽  
Storm Surges ◽  
Water Levels ◽  
Change Scenario ◽  
The World

<p>Coastal areas are one of the most vulnerable regions to climate change given their high exposure to the increasingly frequent extreme sea level (ESL) events and the high population density with around 680 million people (approximately 10% of the world’s population) residing at less than 10 m above sea level and projected to reach more than one billion by 2050 (IPCC, 2019).</p><p>Extreme sea level events include the combination of mean sea level, tides, surges and waves set-up. These events that historically occurred once per century are projected to become at least an annual occurrence at most parts of the world during the 21st century. Therefore, a crucial step towards coastal planning and adaption is the understanding of the drivers and impacts of ESL events (Hinkel et al., 2019).</p><p>Flooding and extreme events in river mouths and their adjacent coastline have a complex nature with oceanic and fluvial processes taking place. Their analysis requires, therefore, the consideration of several physical variables that play a role in water levels such as precipitation, waves, storm surge, and tides. In a climate change scenario, the effects of sea level rise and storminess changes must also be accounted for. The contribution of different processes to ESL events has often been analyzed independently given the difficulty to predict their combined effects.</p><p>This work focuses on the analysis of ESL events due to the combination of sea level rise, extreme waves, storm surges, tides and river flows in a climate change scenario, following:</p><ol><li>Projections of wave variables for an ensemble of EURO-CORDEX RCMs under RCP8.5 using WavewatchIII v5.16 (Besio et al., 2019). Wave propagation of local hydrodynamic processes and storm surge with Delft3D.</li> <li>Projections of river flow using a physical-based and distributed hydrological model under the same runs as the wave climate.</li> <li>Joint statistical characterization of local waves and river flows and long-term temporal variability based on the methodology of Lira-Loarca et al. (2020).</li> <li>Analysis of compound extreme sea level and flooding events.</li> </ol><p>The methodology is applied to a case study in the coast of Granada (Spain) where severe flood events have occurred in recent years. The results highlight the need for an integrated approach encompassing the relevant components of water levels, and specifically sea level rise and waves and the differences in the temporal variability of the significant wave height in a climate change scenario.</p><p> </p><p> </p><p>References:</p><ul><li>Besio et al., 2019. Trends and variability of waves under scenario RCP8.5 in the Mediterranean Sea. 2<sup>nd</sup>International Workshop on Waves, Storm Surges, and Coastal Hazards, Melbourne, Australia</li> <li>Hinkel et al., 2019. Sea level rise and implications for low lying islands, coasts and communities. IPCC SROCC.</li> <li>IPCC, 2019. SPM Special Report on the Ocean and Cryosphere in a Changing Climate.</li> <li>Lira-Loarca et al., 2020. Storm characterization and simulation for damage evolution models of maritime structures. Coastal Engineering, 156, 103620.</li> </ul>

scholarly journals High accuracy coastal flood mapping for Norway using LiDAR data

2019 ◽  
Author(s):  
Kristian Breili ◽  
Matthew James Ross Simpson ◽  
Erlend Klokkervold ◽  
Oda Roaldsdotter Ravndal
Keyword(s):  
At Risk ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Coastal Flooding ◽  
High Accuracy ◽  
Mapping Method ◽  
Water Levels ◽  
Climate Services ◽  
Elevation Data

Abstract. Using new high accuracy Light Detection and Ranging elevation data we generate coastal flooding maps for Norway. Thus far, we have mapped ~ 80 % of the coast, for which we currently have data of sufficient accuracy to perform our analysis. Although Norway is generally at low risk from sea-level rise largely owing to its steep topography, the maps presented here show that on local scales, many parts of the coast are potentially vulnerable to flooding. There is a considerable amount of infrastructure at risk along the relatively long and complicated coastline. Nationwide we identify a total area of 400 km2, 105,000 buildings, and 510 km of roads that are at risk of flooding from a 200 year storm-surge event at present. These numbers will increase to 610 km2, 137,000, and 1340 km with projected sea-level rise to 2090 (95th percentile of RCP8.5 as recommended in planning). We find that some of our results are likely biased high owing to erroneous mapping (at least for lower water levels close to the tidal datum which delineates the coastline). A comparison of control points from different terrain types indicates that the elevation model has a root mean square error of 0.26 m and is the largest source of uncertainty in our mapping method. The coastal flooding maps and associated statistics are freely available, and alongside the development of coastal climate services, will help communicate the risks of sea-level rise and storm surge to stakeholders. This will in turn aid coastal management and climate adaption work in Norway.

Venice lagoon salt marsh vulnerability and halophytic vegetation vertical migration in response to sea level rise

2020 ◽  
Author(s):  
Zhicheng Yang ◽  
Sonia Silvestri ◽  
Marco Marani ◽  
Andrea D’Alpaos
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Current Knowledge ◽  
Venice Lagoon ◽  
Sea Level Changes ◽  
Human Pressure ◽  
Sea Levels ◽  
Vegetation Species

<p>Salt marshes are biogeomorphic systems that provide important ecosystem services such as carbon sequestration and prevention of coastal erosion. These ecosystems are, however, threatened by increasing sea levels and human pressure. Improving current knowledge of salt-marsh response to changes in the environmental forcing is a key step to understand and predict salt-marsh evolution, especially under accelerated sea level rise scenarios and increasing human pressure. Towards this goal, we have analyzed field observations of marsh topographic changes and halophytic vegetation distribution with elevation collected over 20 years (between 2000 and 2019) in a representative marsh in the Venice lagoon (Italy).</p><p>Our results suggest that: 1) on average, marsh elevation with respect to local mean sea level decreased , (i.e. the surface accretion rate was lower than the rate of sea level rise); 2) elevational frequency distributions are characteristic for different halophytic vegetation species, highlighting different ecological realized niches that change in time; 3) although the preferential elevations at which different species have changed in time, the sequence of vegetation species with increasing soil elevation was preserved and simply shifted upward; 4) we observed different vegetation migration rates for the different species, suggesting that the migration process is species-specific. In particular, vegetation species colonizing marsh edges (Juncus and Inula) migrated faster facing to changes in sea levels than Limonium and Spartina , while Sarcocornia was characterized by delayed migration in response to sea level changes. These results bear significant implications for long-term biogeomorphic evolution of tidal environments.</p>

Salt marsh resilience to sea-level rise and increased storm intensity

2021 ◽  
Author(s):  
Natascia Pannozzo ◽  
Nicoletta Leonardi ◽  
Iacopo Carnacina ◽  
Rachel Smedley
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Salt Marshes ◽  
Sediment Budget ◽  
Geophysical Research ◽  
Storm Intensity ◽  
Combined Impact ◽  
And Sea Level

<p>Salt marshes are widely recognised as ecosystems with high economic and environmental value. However, it is still unclear how salt marshes will respond to the combined impact of future sea-level rise and possible increases in storm intensity (Schuerch et al. 2013). This study investigates marsh resilience under the combined impact of various storm surge and sea-level scenarios by using a sediment budget approach. The current paradigm is that a positive sediment budget supports the accretion of salt marshes and, therefore, its survival, while a negative sediment budget causes marsh degradation (Ganju et al. 2015). The Ribble Estuary, North-West England, was used as test case, and the hydrodynamic model Delft3D was used to simulate the response of the salt marsh system to the above scenarios. We conclude that the resilience of salt marshes and estuarine systems is enhanced under the effect of storm surges, as they promote flood dominance and trigger a net import of sediment.  Conversely, sea-level rise threatens marsh stability, by promoting ebb dominance and triggering a net export of sediment. Ultimately, when storm surge and sea-level scenarios are combined, results show that storms with the highest intensities have the potential to counteract the negative impact of sea-level rise by masking its effects on the sediment budget.</p><p><strong>Acknowledgements</strong></p><p>We acknowledge the support of the School of Environmental Sciences, University of Liverpool.</p><p><strong>References</strong></p><p>Ganju, N.K., Kirwan, M.L., Dickhudt, P.J., Guntenspergen, G.R., Cahoon, D.R. and Kroeger, K.D. 2015. “Sediment transport-based metrics of wetland stability”. Geophysical Research Letters, 42(19), 7992-8000.</p><p>Schuerch, M., Vafeidis, A., Slawig, T. and Temmerman, S. 2013. “Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise”. Journal of Geophysical Research-Earth Surface, 118(1),<strong> </strong>84-96.</p>

scholarly journals The Holocene influence on the future evolution of the Venice Lagoon tidal marshes

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Claudia Zoccarato ◽  
Cristina Da Lio
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Past History ◽  
Venice Lagoon ◽  
Tidal Marshes ◽  
Future Evolution ◽  
Sedimentation Dynamics ◽  
History Of ◽  
Present Rate

AbstractThe resilience of marsh ecosystems to expected sea-level rise is determined by a complex interplay of organic and inorganic sedimentation dynamics. Marshes have formed over past centuries to millennia and consist of extremely reactive bodies with sediments that can experience high compaction. Here we provide a quantification of the degree to which the past history of a salt marsh can affect its long-term evolution. A dataset of elevation dynamics was established in the Venice Lagoon (Italy) and interpreted using a physics-based model of deposition and large consolidation of newly deposited material. We found that the fate of low-lying tidal landscapes over the next century of accelerating sea-level rise will be highly dependent on compaction of soft, recently deposited soils. Our results imply that a sedimentation rate twice the present rate will be needed to counterbalance the expected sea-level rise.

scholarly journals Numerical Investigation of Storm Surge in Kong Port in the Persian Gulf

2019 ◽  
Author(s):  
Amir Hossein Mahdavi ◽  
Hamid Ansari Sharghi
Keyword(s):  
Sea Level Rise ◽  
Engineering Design ◽  
Sea Level ◽  
Storm Surge ◽  
Storm Surges ◽  
Wave Model ◽  
Water Level Fluctuations ◽  
Extreme Value Analysis ◽  
Value Analysis ◽  
Mean Sea Level

Storm surge is generated by the integration of waves, tide and wind setup that is resulted in unwanted mean sea level rise and coastal flooding. The estimation of accurate storm surge is essential for the engineering design of coastal structures. In this study, we estimated the respond of mean sea level winds, tide, waves, and sea-level rise using a local coastal model. A fully coupled hydrodynamic and wave model was implemented to obtain storm surge from different phenomena. The simulations of water level fluctuations due to these parameters were analyzed with the wind forces identified with tidal observations in the Port of Kong. Extreme value analysis was performed to determine the fluctuations associated with different return periods. These data were combined by sea-level rise projections are combined with resulted value. The worst and best scenario of storm surges for each return period were determined for engineering design purposes.

scholarly journals Projecting the Effects of Land Subsidence and Sea Level Rise on Storm Surge Flooding in Coastal North Carolina

2021 ◽  
Author(s):  
Jeremy Johnston ◽  
Felicio Cassalho ◽  
Tyler Miesse ◽  
Celso Ferreira
Keyword(s):  
North Carolina ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Land Subsidence ◽  
Relative Rate ◽  
Circulation Model ◽  
Storm Surges ◽  
Fold Increase ◽  
The United States

Abstract Much of the United States Atlantic coastline continues to subside due to post glacial settlement and ground water depletion. Combined with sea level rise (SLR), this contributes to a larger relative rate of SLR regionwide. In this work, we utilize the ADvanced CIRCulation model to simulate storm surges across coastal North Carolina. Simulations of recent Hurricanes Irene (2011) and Matthew (2016) are performed considering SLR projections and land subsidence estimates for the year 2100. The model is validated against historic water level observations with generally strong agreement (mean R2 0.81, RMSE 10–31 cm). At current rates of subsidence, storm surge susceptible regions increase on the order of 30–40% by 2100 relative to near-present day conditions. Flood water redistribution leaves low-lying areas especially vulnerable, as many of which also experience increased land subsidence. Combined with SLR projections, results project more than a doubling of areal flood extent for Hurricane Irene from ~ 2,000 km2 (2011) to 5,000 km2 (2100, subsidence + 74 cm), and more than a 3-fold increase ~ 1,400 km2 (2016) to 4,900 km2 (2100, subsidence + 74 cm) for Hurricane Matthew. The expected inundation increases have substantial implications for communities and ecosystems located in coastal North Carolina.

scholarly journals Modeling the Impacts of Sea Level Rise on Storm Surge Inundation in Flood-Prone Urban Areas of Hampton Roads, Virginia

2018 ◽  
Vol 52 (2) ◽  
pp. 92-105 ◽  
Author(s):  
Luca Castrucci ◽  
Navid Tahvildari
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Hydrodynamic Model ◽  
Urban Areas ◽  
The United States ◽  
Hampton Roads ◽  
Level Data ◽  
The Difference ◽  
Surge Flooding

AbstractHampton Roads is a populated area in the United States Mid-Atlantic region that is highly affected by sea level rise (SLR). The transportation infrastructure in the region is increasingly disrupted by storm surge and even minor flooding events. The purpose of this study is to improve our understanding of SLR impacts on storm surge flooding in the region. We develop a hydrodynamic model to study the vulnerability of several critical flood-prone neighborhoods to storm surge flooding under several SLR projections. The hydrodynamic model is validated for tide prediction, and its performance in storm surge simulation is validated with the water level data from Hurricane Irene (2011). The developed model is then applied to three urban flooding hotspots located in Norfolk, Chesapeake, and the Isle of Wight. The extent, intensity, and duration of storm surge inundation under different SLR scenarios are estimated. Furthermore, the difference between the extent of flooding as predicted by the hydrodynamic model and the “bathtub” approach is highlighted.

scholarly journals High-accuracy coastal flood mapping for Norway using lidar data

2020 ◽  
Vol 20 (2) ◽  
pp. 673-694
Author(s):  
Kristian Breili ◽  
Matthew James Ross Simpson ◽  
Erlend Klokkervold ◽  
Oda Roaldsdotter Ravndal
Keyword(s):  
At Risk ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Climate Adaptation ◽  
Coastal Flooding ◽  
High Accuracy ◽  
Water Levels ◽  
Land Uplift ◽  
Climate Services

Abstract. Using new high-accuracy light detection and ranging (lidar) elevation data we generate coastal flooding maps for Norway. Thus far, we have mapped ∼80 % of the coast, for which we currently have data of sufficient accuracy to perform our analysis. Although Norway is generally at low risk from sea level rise largely owing to its steep topography and land uplift due to glacial isostatic adjustment, the maps presented here show that, on local scales, many parts of the coast are potentially vulnerable to flooding. There is a considerable amount of infrastructure at risk along the relatively long and complicated coastline. Nationwide we identify a total area of 400 km2, 105 000 buildings, and 510 km of roads that are at risk of flooding from a 200-year storm surge event at present. These numbers will increase to 610 km2, 137 000, and 1340 km with projected sea level rise to 2090 (95th percentile of RCP8.5 as recommended in planning). We find that some of our results are likely biased high owing to erroneous mapping (at least for lower water levels close to the tidal datum which delineates the coastline). A comparison of control points from different terrain types indicates that the elevation model has a root-mean-square error of 0.26 m and is the largest source of uncertainty in our mapping method. The coastal flooding maps and associated statistics are freely available, and alongside the development of coastal climate services, will help communicate the risks of sea level rise and storm surge to stakeholders. This will in turn aid coastal management and climate adaptation work in Norway.

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