Apr 30

Publication | Data and numerical analysis of astronomic tides, wind-waves, and hurricane storm surge along the northern Gulf of Mexico

All_spatial_HWM_GagePeaksM.V. Bilskie, S.C. Hagen, S.C. Medeiros, A.T. Cox, M. Salisbury, D. Coggin  (2016). “Data and numerical analysis of astronomic tides, wind-waves, and hurricane storm surge along the northern Gulf of Mexico.” Journal of Geophysical Research, In Press. doi: 10.1002/2015JC011400.

Abstract The northern Gulf of Mexico (NGOM) is a unique geophysical setting for complex tropical storm-induced hydrodynamic processes that occur across a variety of spatial and temporal scales. Each hurricane includes its own distinctive characteristics and can cause unique and devastating storm surge when it strikes within the intricate geometric setting of the NGOM. While a number of studies have explored hurricane storm surge in the NGOM, few have attempted to describe storm surge and coastal inundation using observed data in conjunction with a single large-domain high-resolution numerical model. To better understand the oceanic and nearshore response to these tropical cyclones, we provide a detailed assessment, based on field measurements and numerical simulation, of the evolution of wind waves, water levels, and currents for Hurricanes Ivan (2004), Dennis (2005), Katrina (2005), and Isaac (2012), with focus on Mississippi, Alabama, and the Florida Panhandle coasts. The developed NGOM3 computational model describes the hydraulic connectivity among the various inlet and bay systems, Gulf Intracoastal Waterway, coastal rivers and adjacent marsh, and built infrastructure along the coastal floodplain. The outcome is a better understanding of the storm surge generating mechanisms and interactions among hurricane characteristics and the NGOM’s geophysical configuration. The numerical analysis and observed data explain the ∼2 m/s hurricane-induced geostrophic currents across the continental shelf, a 6 m/s outflow current during Ivan, the hurricane-induced coastal Kelvin wave along the shelf, and for the first time a wealth of measured data and a detailed numerical simulation was performed and was presented for Isaac. This article is protected by copyright. All rights reserved.

Permanent link to this article: http://www.mattbilskie.com/publication-data-and-numerical-analysis-of-astronomic-tides-wind-waves-and-hurricane-storm-surge-along-the-northern-gulf-of-mexico/

Apr 23

Publication | Dynamic simulation and numerical analysis of hurricane storm surge under sea level rise with geomorphologic changes along the northern Gulf of Mexico

StormTracksM.V. Bilskie, S.C. Hagen, K. Alizad, S.C. Medeiros, D.L. Passeri, H.F. Needham, A. Cox (2016). “Dynamic simulation and numerical analysis of hurricane storm surge under sea level rise with geomorphologic changes along the northern Gulf of Mexico.” Earth’s Future, In Press. doi: 10.1002/2015EF000347

Abstract This work outlines a dynamic modeling framework to examine the effects of global climate change, and sea level rise (SLR) in particular, on tropical cyclone-driven storm surge inundation. The methodology, applied across the northern Gulf of Mexico, adapts a present day large-domain, high resolution, tide, wind-wave, and hurricane storm surge model to characterize the potential outlook of the coastal landscape under four SLR scenarios for the year 2100. The modifications include shoreline and barrier island morphology, marsh migration, and land use land cover change. Hydrodynamics of ten historic hurricanes were simulated through each of the five model configurations (present day and four SLR scenarios). Under SLR, the total inundated land area increased by 87% and developed and agricultural lands by 138% and 189%, respectively. Peak surge increased by as much as 1 m above the applied SLR in some areas, and other regions were subject to a reduction in peak surge, with respect to the applied SLR, indicating a nonlinear response. Analysis of time-series water surface elevation suggests the interaction between SLR and storm surge is nonlinear in time; SLR increased the time of inundation and caused an earlier arrival of the peak surge, which cannot be addressed using a static (“bathtub”) modeling framework. This work supports the paradigm shift to using a dynamic modeling framework to examine the effects of global climate change on coastal inundation. The outcomes have broad implications and ultimately support a better holistic understanding of the coastal system and aid restoration and long-term coastal sustainability.

Permanent link to this article: http://www.mattbilskie.com/publication-dynamic-simulation-and-numerical-analysis-of-hurricane-storm-surge-under-sea-level-rise-with-geomorphologic-changes-along-the-northern-gulf-of-mexico/

Apr 23

Publication | Tidal hydrodynamics under future sea level rise and coastal morphology in the northern Gulf of Mexico

Morph_FlowChart

D.L. Passeri, S.C. Hagen, M.V. Bilskie, S.C. Medeiros, K. Alizad (2016). “Tidal hydrodynamics under future sea level rise and coastal morphology in the northern Gulf of Mexico.” Earth’s Future, Online 4/4/2016.

Abstract 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) due to increases in the inlet-cross-sectional area. Changes in harmonic constituent phases indicated 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.

Permanent link to this article: http://www.mattbilskie.com/publication-tidal-hydrodynamics-under-future-sea-level-rise-and-coastal-morphology-in-the-northern-gulf-of-mexico/

Feb 15

Publication | A Coupled, two-dimensional hydrodynamic-marsh model with biological feedback

 

HYDRO-MEM

K. Alizad, S.C. Hagen, J.T. Morris, P. Bacopoulos, M.V. Bilskie, J.F. Weishampel, S.C. Medeiros (2016). “A coupled, two-dimensional hydrodynamic-marsh model with biological feedback.” Ecological Modeling, 327, 29-43,  http://dx.doi.org/10.1016/j.ecolmodel.2016.01.013

Abstract A spatially-explicit model (Hydro-MEM model) that couples astronomic tides and Spartina alterniflora dynamics was developed to examine the effects of sea-level rise on salt marsh productivity in northeast Florida. The hydrodynamic component of the model simulates the hydroperiod of the marsh surface driven by astronomic tides and the marsh platform topography, and demonstrates biophysical feedback that non- uniformly modifies marsh platform accretion, plant biomass, and water levels across the estuarine landscape, forming a complex geometry. The marsh platform accretes organic and inorganic matter depending on the sediment load and biomass density which are simulated by the ecological-marsh component (MEM) of the model and are functions of the hydroperiod. Two sea-level rise projections for the year 2050 were simulated: 11 cm (low) and 48 cm (high). Overall biomass density increased under the low sea-level rise scenario by 54% and declined under the high sea-level rise scenario by 21%. The biomassdriven topographic and bottom friction parameter updates were assessed by demonstrating numerical convergence (the state where the difference between biomass densities for two different coupling time steps approaches a small number). The maximum coupling time steps for low and high sea-level rise cases were calculated to be 10 and 5 years, respectively. A comparison of the Hydro-MEM model with a parametric marsh equilibrium model (MEM) indicates improvement in terms of spatial pattern of biomass distribution due to the coupling and dynamic sea-level rise approaches. This integrated Hydro-MEM model provides an innovative method by which to assess the complex spatial dynamics of salt marsh grasses and predict the impacts of possible future sea level conditions.

Permanent link to this article: http://www.mattbilskie.com/publication-a-coupled-two-dimensional-hydrodynamic-marsh-model-with-biological-feedback/

Jan 04

2015 AGU Fall Meeting Presentation

StormTracksM.V. Bilskie, S.C. Hagen, D.L. Passeri,  K. Alizad, S.C. Medeiros, J.L. Irish, H. Needham, and A. Cox, “A dynamic flood inundation model framework to assess coastal flood risk in a changing climate.” 2015 AGU Fall Meeting, San Francisco, CA, Dec. 14-18, 2015.

Session GC032: Field/Laboratory Analysis, Modeling, and Stakeholder Involvement to Assess Impacts of the Coastal Dynamics of Sea Level Rise in Low Gradient Coastal Landscapes

Session ID: 8261

Abstract: Coastal regions around the world are susceptible to a variety of natural disasters causing extreme inundation. It is anticipated that the vulnerability of coastal cities will increase due to the effects of climate change, and in particular sea level rise (SLR). A novel framework was developed to generate a suite of physics-based storm surge models that include projections of coastal floodplain dynamics under climate change scenarios: shoreline erosion/accretion, dune morphology, salt marsh migration, and population dynamics [Bilskie et al., 2014; Passeri et al., 2014; Passeri et al., 2015].

First, the storm surge inundation model was extensively validated for present day conditions with respect to astronomic tides and hindcasts of Hurricane Ivan (2004), Dennis (2005), Katrina (2005), and Isaac (2012). The model was then modified to characterize the future outlook of the landscape for four climate change scenarios for the year 2100 (B1, B2, A1B, and A2), and each climate change scenario was linked to a sea level rise of 0.2 m, 0.5 m, 1.2 m, and 2.0 m [Parris et al., 2012]. The adapted model was then used to simulate hurricane storm surge conditions for each climate scenario using a variety of tropical cyclones as the forcing mechanism. The collection of results shows the intensification of inundation area and the vulnerability of the coast to potential future climate conditions. The methodology developed herein to assess coastal flooding under climate change can be performed across any coastal region worldwide, and results provide awareness of regions vulnerable to extreme flooding in the future.

References

Bilskie, M. V., S. C. Hagen, S. C. Medeiros, and D. L. Passeri (2014), Dynamics of sea level rise and coastal flooding on a changing landscape, Geophysical Research Letters, 41(3), 927-934.

Parris, A., et al. (2012), Global Sea Level Rise Scenarios for the United States National Climate AssessmentRep., 37 pp.

Passeri, D. L., S. C. Hagen, M. V. Bilskie, and S. C. Medeiros (2014), On the significance of incorporating shoreline changes for evaluating coastal hydrodynamics under sea level rise scenarios, Natural Hazards, 1599-1617.

Passeri, D. L., S. C. Hagen, S. C. Medeiros, M. V. Bilskie, K. Alizad, and D. Wang (2015), The dynamic effects of sea level rise on low gradient coastal landscapes: a review, Earth’s Future, 3.

Permanent link to this article: http://www.mattbilskie.com/2015-agu-fall-meeting-presentation/

Oct 05

Publication | Terrain-driven unstructured mesh development through semi-automatic vertical feature extraction

AWR_Figure2

M.V. Bilskie, D. Coggin, S.C. Hagen, S.C. Medeiros (2015). “Terrain-driven unstructured mesh development through semi-automatic vertical feature extraction.” Adv. Water Resources, doi:10.1016/j.advwatres.2015.09.020

Abstract: A semi-automated vertical feature terrain extraction algorithm is described and applied to a two-dimensional, depth-integrated, shallow water equation inundation model. The extracted features describe what are commonly sub-mesh scale elevation details (ridge and valleys), which may be ignored in standard practice because adequate mesh resolution cannot be afforded. The extraction algorithm is semi-automated, requires minimal human intervention, and is reproducible. A lidar-derived Digital Elevation Model (DEM) of coastal Mississippi and Alabama serves as the source data for the vertical feature extraction. Unstructured mesh nodes and element edges are aligned to the vertical features and an interpolation algorithm aimed at minimizing topographic elevation error assigns elevations to mesh nodes via the DEM. The end result is a mesh that accurately represents the bare earth surface as derived from lidar with element resolution in the floodplain ranging from 15 m to 200 m. To examine the influence of the inclusion of vertical features on overland flooding, two additional meshes were developed, one without crest elevations of the features and another with vertical features withheld. All three meshes were incorporated into a SWAN+ADCIRC model simulation of Hurricane Katrina. Each of the three models resulted in similar validation statistics when compared to observed time-series water levels at gages and post-storm collected high water marks. Simulated water level peaks yielded an R2 of 0.97 and upper and lower 95% confidence interval of ∼ ± 0.60 m. From the validation at the gages and HWM locations, it was not clear which of the three model experiments performed best in terms of accuracy. Examination of inundation extent among the three model results were compared to debris lines derived from NOAA post-event aerial imagery, and the mesh including vertical features showed higher accuracy. The comparison of model results to debris lines demonstrates that additional validation techniques are necessary for state-of-the-art flood inundation models. In addition, the semi-automated, unstructured mesh generation process presented herein increases the overall accuracy of simulated storm surge across the floodplain without reliance on hand digitization or sacrificing computational cost.

Permanent link to this article: http://www.mattbilskie.com/publication-terrain-driven-unstructured-mesh-development-through-semi-automatic-vertical-feature-extraction/

Jul 13

Presentation | University of Cambridge

MOM_Compare_MSAL

M.V. Bilskie, S.C. Hagen, K. Alizad, S.C. Medeiros, D.L. Passeri, J.L. Irish, & N. Plant, “Assessment of coastal flood risk in a changing climate.” University of Cambridge, Cambridge, UK, July 9, 2015

Last week, I had the opportunity to give a talk at the University of Cambridge to the Cambridge Coastal Research Unit (CCRU). Much thanks to Anna for organizing the event!

Abstract: Coastal regions around the world are susceptible to a variety of natural disasters causing extreme inundation. It is anticipated that the vulnerability of coastal cities will increase due to the effects of climate change, and in particular sea level rise (SLR). A novel framework has been developed to construct a physics-based storm surge model that includes projections of coastal floodplain dynamics under climate change scenarios. Numerous experiments were conducted and it was concluded that a number of influencing factors, other than SLR, should be included in future assessments of coastal flooding under climate change; e.g., shoreline changes, barrier island morphology, salt marsh evolution, and population dynamics. These factors can significantly affect the path, pattern, and magnitude of flooding depths and inundation along the coastline. Using these factors, a storm surge model of the northern Gulf of Mexico, U.S. (NGOM) representing present day conditions is modified to characterize the future outlook of the landscape. This adapted model is then used to assess flood risk in terms of the 100-year floodplain surface under various climate change scenarios. The collection of results facilitate the estimation and projection of potential future flood risk. This novel method to assess coastal flooding under climate change can be performed across any coastal region worldwide, and results provide awareness of regions vulnerable to extreme flooding in the future.

Permanent link to this article: http://www.mattbilskie.com/presentation-university-of-cambridge/

Jul 13

Conference | 36th IAHR World Congress

StaticvsDynamicM.V. Bilskie, S.C. Hagen & J. Irish, “Development of future tropical cyclone 100-year floodplains in a changing climate” 36th IAHR World Congress, Delft-The Hague, The Netherlands, June 28 – July 3, 2015.

Permanent link to this article: http://www.mattbilskie.com/conference-36th-iahr-world-congress/

May 08

Publication | The dynamic effects of sea level rise on low gradient coastal landscapes: a review

SLR_EnchroachD.L. Passeri, S.C. Hagen, S.C. Medeiros, M.V. Bilskie, K. Alizad, D. Wang (2015). “The dynamic effects of sea level rise on low gradient coastal landscapes: a review.” AGU Earth’s Future, doi:10.1002/2015EF000298

Abstract: 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 non-additively to SLR. Coastal morphology continually adapts towards 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.

Permanent link to this article: http://www.mattbilskie.com/publication-the-dynamic-effects-of-sea-level-rise-on-low-gradient-coastal-landscapes-a-review/

Apr 16

2015 LA ASCE Conference| Storm surge modeling in the northern Gulf of Mexico

M.V. Bilskie, S.C. Hagen, D.L. Passeri, K. Alizad, S.C. Medeiros, D. Coggin, J.L. Irish, N. Plant, A. Cox, C. Kaiser “Tide, wind-wave & hurricane storm surge modelling in the northern Gulf of Mexico under climate change.” 2015 ASCE Louisiana Section Spring Conference, Baton Rouge, LA, April 16-17, 2015.

Permanent link to this article: http://www.mattbilskie.com/2015-la-asce-conference-storm-surge-modeling-in-the-northern-gulf-of-mexico/

Load more