Unstructured Finite Element Mesh Decimation for Real Time Hurricane Storm Surge Forecasting

Motivation: Provide real time decision support Emergency mangers are interested in… When will the water rise? What height will it get? How long will it stay? Who will be impacted? Will mesh decimation give accurate results in order to predict forecasted water levels for storms in a faster time frame than is currently used by larger meshes

Development of a High-Resolution, Wind-Wave, Tide, and Hurricane Storm Surge Model for Southern Mississippi

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

The Quest for the Missing Dust: II -- Two Orders of Magnitude of Evolution in the Dust-to-Gas Ratio Resolved Within Local Group Galaxies

We explore evolution in the dust-to-gas ratio with density within four well-resolved Local Group galaxies - the LMC, SMC, M31, and M33. We do this using new ${\it Herschel}$ maps, which restore extended emission that was missed by previous ${\it Herschel}$ reductions. This improved data allows us to probe the dust-to-gas ratio across 2.5 orders of magnitude in ISM surface density. We find significant evolution in the dust-to-gas ratio, with dust-to-gas varying with density within each galaxy by up to a factor 22.4. We explore several possible reasons for this, and our favored explanation is dust grain growth in denser regions of ISM. We find that the evolution of the dust-to-gas ratio with ISM surface density is very similar between M31 and M33, despite their large differences in mass, metallicity, and star formation rate; conversely, we find M33 and the LMC to have very different dust-to-gas evolution profiles, despite their close similarity in those properties. Our dust-to-gas ratios address previous disagreement between UV- and FIR-based dust-to-gas estimates for the Magellanic Clouds, removing the disagreement for the LMC, and considerably reducing it for the SMC - with our new dust-to-gas measurements being factors of 2.4 and 2.0 greater than the previous far-infrared estimates, respectively. We also observe that the dust-to-gas ratio appears to fall at the highest densities for the LMC, M31, and M33; this is unlikely to be an actual physical phenomenon, and we posit that it may be due to a combined effect of dark gas, and changing dust mass opacity.Comment: Accepted for publication in the Astrophysical Journa

The Dynamic Effects of Sea Level Rise on Low-Gradient Coastal Landscapes: A Review

Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shoreline erosion, and increased flooding during storm events. Hydrodynamic parameters such as tidal ranges, tidal prisms, tidal asymmetries, increased flooding depths and inundation extents during storm events respond nonadditively to SLR. Coastal morphology continually adapts toward equilibrium as sea levels rise, inducing changes in the landscape. Marshes may struggle to keep pace with SLR and rely on sediment accumulation and the availability of suitable uplands for migration. Whether hydrodynamic, morphologic, or ecologic, the impacts of SLR are interrelated. To plan for changes under future sea levels, coastal managers need information and data regarding the potential effects of SLR to make informed decisions for managing human and natural communities. This review examines previous studies that have accounted for the dynamic, nonlinear responses of hydrodynamics, coastal morphology, and marsh ecology to SLR by implementing more complex approaches rather than the simplistic “bathtub” approach. These studies provide an improved understanding of the dynamic effects of SLR on coastal environments and contribute to an overall paradigm shift in how coastal scientists and engineers approach modeling the effects of SLR, transitioning away from implementing the “bathtub” approach. However, it is recommended that future studies implement a synergetic approach that integrates the dynamic interactions between physical and ecological environments to better predict the impacts of SLR on coastal systems

The Dynamic Effects of Sea Level Rise on Low‐Gradient Coastal Landscapes: A Review

Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shore-line erosion, and increased flooding during storm events. Hydrodynamic parameters such as tidal ranges, tidal prisms, tidal asymmetries, increased flooding depths and inundation extents during storm events respond non additively to SLR. Coastal morphology continually adapts toward equilibrium as sea levels rise, inducing changes in the landscape. Marshes may struggle to keep pace with SLR and rely on sediment accumulation and the availability of suitable uplands for migration. Whether hydrodynamic, morphologic, or ecologic, the impacts of SLR are interrelated. To plan for changes under future sea lev-els, coastal managers need information and data regarding the potential effects of SLR to make informed decisions for managing human and natural communities. This review examines previous studies that have accounted for the dynamic, nonlinear responses of hydrodynamics, coastal morphology, and marsh ecol-ogy to SLR by implementing more complex approaches rather than the simplistic “bathtub” approach. These studies provide an improved understanding of the dynamic effects of SLR on coastal environments and contribute to an overall paradigm shift in how coastal scientists and engineers approach modeling the effects of SLR, transitioning away from implementing the “bathtub” approach. However, it is recommended that future studies implement a synergetic approach that integrates the dynamic interactions between physical and ecological environments to better predict the impacts of SLR on coastal systems

Integrated Modeling of Dynamic Marsh Feedbacks and Evolution Under Sea-Level Rise in a Mesotidal Estuary (Plum Island, MA, USA)

Around the world, wetland vulnerability to sea-level rise (SLR) depends on different factors including tidal regimes, topography, creeks and estuary geometry, sediment availability, vegetation type, etc. The Plum Island estuary (PIE) is a mesotidal wetland system on the east coast of the United States. This research applied a newly updated Hydro-MEM (integrated hydrodynamic-marsh) model to assess the impacts of intermediate-low (50 cm), intermediate (1 m), and intermediate-high (1.5 m) SLR on marsh evolution by the year 2100. Model advancements include capturing vegetation change, inorganic and below and aboveground organic matter portion of marsh platform accretion, and mudflat creation. Although the results indicate a low vulnerability marsh at the PIE, the vegetation changes from high to low marsh under all SLR scenarios (2%–22%), with the higher bounds belonging to higher rise scenarios. Lower SLR produces more productive marsh (13% gain in high productivity regions), whereas the highest SLR scenario causes increased tidal inundation, which leads to loss in productivity (12% change from high to low productivity regions), generation of mudflats (17% of the domain land), and marsh migration to higher lands. Sensitive nonlinear tidal flow changes, which may be increased or decreased with SLR as a result of mudflat creation, marsh migration, and bottom friction change, emphasize the importance of integrated modeling approaches that include dynamic marsh feedbacks in hydrodynamic modeling and varying hydrodynamic effects on the marsh system

Coastal Wetland Response to Sea-Level Rise in a Fluvial Estuarine System

Coastal wetlands are likely to lose productivity under increasing rates of sea-level rise (SLR). This study assessed a fluvial estuarine salt marsh system using the Hydro-MEM model under four SLR scenarios. The Hydro-MEM model was developed to apply the dynamics of SLR as well as capture the effects associated with the rate of SLR in the simulation. Additionally, the model uses constants derived from a 2-year bioassay in the Apalachicola marsh system. In order to increase accuracy, the lidar-based marsh platform topography was adjusted using Real Time Kinematic survey data. A river inflow boundary condition was also imposed to simulate freshwater flows from the watershed. The biomass density results produced by the Hydro-MEM model were validated with satellite imagery. The results of the Hydro-MEM simulations showed greater variation of water levels in the low (20 cm) and intermediate-low (50 cm) SLR scenarios and lower variation with an extended bay under higher SLR scenarios. The low SLR scenario increased biomass density in some regions and created a more uniform marsh platform in others. Under intermediate-low SLR scenario, more flooded area and lower marsh productivity were projected. Higher SLR scenarios resulted in complete inundation of marsh areas with fringe migration of wetlands to higher land. This study demonstrated the capability of Hydro-MEM model to simulate coupled physical/biological processes across a large estuarine system with the ability to project marsh migration regions and produce results that can aid in coastal resource management, monitoring, and restoration efforts

Tidal Hydrodynamics Under Future Sea Level Rise and Coastal Morphology in the Northern Gulf of Mexico

This study examines the integrated influence of sea level rise (SLR) and future morphology on tidal hydrodynamics along the Northern Gulf of Mexico (NGOM) coast including seven embayments and three ecologically and economically significant estuaries. A large-domain hydrodynamic model was used to simulate astronomic tides for present and future conditions (circa 2050 and 2100). Future conditions were simulated by imposing four SLR scenarios to alter hydrodynamic boundary conditions and updating shoreline position and dune heights using a probabilistic model that is coupled to SLR. Under the highest SLR scenario, tidal amplitudes within the bays increased as much as 67% (10.0 cm) because of increases in the inlet cross-sectional area. Changes in harmonic constituent phases indicated that tidal propagation was faster in the future scenarios within most of the bays. Maximum tidal velocities increased in all of the bays, especially in Grand Bay where velocities doubled under the highest SLR scenario. In addition, the ratio of the maximum flood to maximum ebb velocity decreased in the future scenarios (i.e., currents became more ebb dominant) by as much as 26% and 39% in Weeks Bay and Apalachicola, respectively. In Grand Bay, the flood-ebb ratio increased (i.e., currents became more flood dominant) by 25% under the lower SLR scenarios, but decreased by 16% under the higher SLR as a result of the offshore barrier islands being overtopped, which altered the tidal prism. Results from this study can inform future storm surge and ecological assessments of SLR, and improve monitoring and management decisions within the NGOM

Coastal Wetland Response to Sea‐Level Rise in a Fluvial Estuarine System

Coastal wetlands are likely to lose productivity under increasing rates of sea‐level rise (SLR). This study assessed a fluvial estuarine salt marsh system using the Hydro‐MEM model under four SLR scenarios. The Hydro‐MEM model was developed to apply the dynamics of SLR as well as capture the effects associated with the rate of SLR in the simulation. Additionally, the model uses constants derived from a 2‐year bioassay in the Apalachicola marsh system. In order to increase accuracy, the lidar‐based marsh platform topography was adjusted using Real Time Kinematic survey data. A river inflow boundary condition was also imposed to simulate freshwater flows from the watershed. The biomass density results produced by the Hydro‐MEM model were validated with satellite imagery. The results of the Hydro‐MEM simulations showed greater variation of water levels in the low (20 cm) and intermediate‐low (50 cm) SLR scenarios and lower variation with an extended bay under higher SLR scenarios. The low SLR scenario increased biomass density in some regions and created a more uniform marsh platform in others. Under intermediate‐low SLR scenario, more flooded area and lower marsh productivity were projected. Higher SLR scenarios resulted in complete inundation of marsh areas with fringe migration of wetlands to higher land. This study demonstrated the capability of Hydro‐MEM model to simulate coupled physical/biological processes across a large estuarine system with the ability to project marsh migration regions and produce results that can aid in coastal resource management, monitoring, and restoration efforts