Aug 29

Visualization of Hurricane Michael | PEARC19

Below is a scientific rendering of our simulation results for Hurricane Michael on the high-resolution NGOM3 mesh. This effort is a product of the XSEDE ECSS Program. Thanks to David Bock at the University of Illinois National Center for Supercomputing Applications for being part of this project!

Abstract Hurricane Michael made landfall near Mexico Beach, FL on October 10 as a Category 5 storm. Measurements of peak water levels revealed storm surge as high as to 4.37 m (NAVD88). Areas surrounding Mexico Beach, Port St. Joe, St. George Island, and Apalachicola experienced wide-spread flooding and extensive damage. To gain an understanding of storm surge and related overland flooding, we simulate the water level and wave response from Hurricane Michael using a tightly-coupled ADCIRC+SWAN model of the northern Gulf of Mexico (NGOM), NGOM3. The ADCIRC (Advanced Circulation) code computes water levels and depth-averaged currents via the shallow water equations while SWAN (Simulating Waves Nearshore) computes relative frequency and direction of wind-waves from the action balance equation. Both models utilize the same NGOM3 unstructured finite element mesh (5.5 million nodes) that spans the western north Atlantic Ocean, Caribbean Sea, and Gulf of Mexico and includes detailed representation of the Mississippi, Alabama, and Florida panhandle coastal floodplain. Model resolution ranges from 20 m – 200 m across the overland regions and describes the significant hydraulic features such as bay/inlet systems, sounds, estuaries, coastal river, and the Gulf Intracoastal Waterway that can convey or inhibit storm surge flows. The NGOM3 model is a result of over a decade of effort and improvements. A custom visualization system is used to visualize a variety of parameters including wave height, water surface elevation, wind, and current.

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Jun 25

Publication | A comprehensive review of compound inundation models in low-gradient coastal watersheds

F.L. Santiago-Collazo*, M.V. Bilskie, S.C. Hagen (2019). “A  comprehensive review of compound inundation models.” Environmental Modelling & Software. 119, pp. 166-181.

Abstract Extreme coastal flooding poses a major threat to human life and infrastructure. Low-gradient coastal watersheds can be vulnerable to flooding from both intense rainfall and storm surge. Here we present a comprehensive review of the most recent studies that quantify extreme flooding using variations of a compound inundation model. A compound inundation model may consist of different numerical models, observed data, and/or a combination of these. The definitions, advantages, and limitations of each joining technique are discussed with the goal of enabling and focusing subsequent research. Future investigation should focus on the development of a tight-coupling procedure that can accurately represent the complex physical interactions between storm surge and rainfall-runoff. A more accurate compound flood forecast tool can help decision-makers, stakeholders and authorities converge on better coastal resiliency measures that can potentially save human lives, aid in the design of structures and communities, and decrease property damage.

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May 01

Publication | Assessment of the temporal evolution of storm surge across coastal Louisiana

C.G. Siverd, S.C. Hagen, M.V. Bilskie, D.H. Braud, S. Gao, R.H. Peele, R.R. Twilley (2019). “Assessment of the temporal evolution of storm surge across coastal Louisiana.” Coastal Engineering, 150, pp. 59-78.

Abstract The co-evolution of wetland loss and flood risk in the Mississippi River Delta is tested by contrasting the response of storm surge in coastal basins with varying historical riverine sediment inputs. A previously developed method to construct hydrodynamic storm surge models is employed to quantify historical changes in coastal storm surge. Simplified historical landscapes facilitate comparability while storm surge model meshes developed from historical data are incomparable due to the only recent (post-2000) extensive use of lidar for topographic mapping. Storm surge model meshes circa 1930, 1970 and 2010 are constructed via application of land to water (L:W) isopleths, lines that indicate areas of constant land to water ratio across coastal Louisiana. The ADvanced CIRCulation (ADCIRC) code, coupled with the Simulating WAves Nearshore (SWAN) wave model, is used to compute water surface elevations, time of inundation, depth-averaged currents and wave statistics from a suite of 14 hurricane wind and pressure fields for each mesh year. Maximum water surface elevation and inundation time differences correspond with coastal basins featuring historically negligible riverine sediment inputs and wetland loss as well as a coastal basin with historically substantial riverine inputs and wetland gain. The major finding of this analysis is maximum water surface elevations differences from 1970 to 2010 are 0.247 m and 0.282 m within sediment-starved Terrebonne and Barataria coastal basins, respectively. This difference is only 0.096 m across the adjacent sediment-abundant Atchafalaya-Vermilion coastal basin. Hurricane Rita inundation time results from 1970 to 2010 demonstrate an increase of approximately one day across Terrebonne and Barataria while little change occurs across Atchafalaya-Vermilion. The connection between storm surge characteristics and changes in riverine sediment inputs is also demonstrated via a sensitivity analysis which identifies changes in sediment inputs as the greatest contributor to changes in storm surge when compared with historical global mean sea level (GMSL) rise and the excavation of major navigation waterways. Results imply the magnitude of the challenge of preparing this area for future subsidence and GMSL rise.

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Mar 28

Publication | Advancing the Understanding of Storm Processes and Impacts

N Elko, JC Dietrich, M Cialone, H Stockdon, MV Bilskie, B Boyd, B Charbonneau, D Cox, KM Dresback, S Elgar, A Lewis, P Limber, J Long, TC Massey, T Mayo, K McIntosh, N Nadal-Caraballo, B Raubenheimer, T Tomiczek, A Wargula (2019). “Advancing the Understanding of Storm Processes and Impacts.” Shore & Beach, 87(1), 41-55.

Abstract In 2017, Hurricanes Harvey, Irma, and Maria caused more than $200 billion dollars of damage in the United States, as well as the incalculable cost of the loss of life and mental trauma associated with these disasters. In a changing climate, sea level rise and the potential for increasing tropical cyclone intensity can result in even more devastating damages. Therefore, engineers, community planners, and coastal residents need accurate, timely, and accessible forecasting of storm processes and their impact on coastal communities to bolster national resilience and reduce risk to life and property during these events. However, along with uncertainties in understanding and modeling of storm processes, there are complex challenges associated with determining and meeting the needs of end users who rely on these forecasts for emergency management decisions.

To determine needed advancements in storm forecasting, the U.S. Coastal Research Program (USCRP) hosted a Storm Processes and Impacts workshop for coastal stakeholders 16-18 April 2018, in St. Petersburg, Florida. The attendees included local coastal managers, emergency managers, state and regional agencies, federal agency scientists and engineers, academics, and private industry scientists and engineers. Workshop objectives were to synthesize present capabilities for modeling storm processes and forecasting impacts and to prioritize advancements. In addition, the workshop provided an opportunity to bridge the apparent gap between the research of coastal scientists and engineers and the information being distributed publicly and to emergency managers before, during, and after storm events.

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Jan 04

Publication | Development of Return Period Stillwater Floodplains for the Northern Gulf of Mexico under the Coastal Dynamics of Sea Level Rise

M.V. Bilskie, S.C. Hagen, J. Irish (2018). “Development of return period stillwater floodplains for the northern Gulf of Mexico under the coastal dynamics of sea level rise.” ASCE Journal of Waterway, Port, Coastal, and Ocean Engineering, 145(2),

Abstract Rising seas increase the exposure, vulnerability, and thus the risk associated with hurricane storm surge flooding across the coastal floodplain. A methodology is applied to down select a suite of synthetic storms from recent flood insurance studies. The purpose is to force wind-wave and hurricane storm surge models of the northern Gulf of Mexico (NGOM) coast (Mississippi, Alabama, and the Florida Panhandle) that represent the future landscape and derive the 1 and 0.2% annual chance floodplain for present-day and four sea-level-rise (SLR) scenarios. Vast new regions become part of the 100-year floodplain by the end of the century. In Mississippi, the present-day 500-year return period event is likely to be the 100-year event under an SLR of 1.2 m. Throughout most of Alabama and the Florida Panhandle, the present-day 500-year return period event becomes a 100-year event with just 0.5 m of SLR. Results indicate the need to apply a coastal dynamic modeling approach to plan and prepare for the effects of SLR across the NGOM and other low-gradient coastal landscapes.

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Apr 09

Publication | Defining Flood Zone Transitions in Low‐Gradient Coastal Regions

M.V. Bilskie & S.C. Hagen (2018). “Defining Flood Zone Transitions in Low-Gradient Coastal Regions.” Geophysical Research Letters, In Press, doi: 10.1002/2018GL077524.

Abstract Worldwide, coastal, and deltaic communities are susceptible to flooding from the individual and combined effects of rainfall excess and astronomic tide and storm surge inundation. Such flood events are a present (and future) cause of concern as observed from recent storms such as the 2016 Louisiana flood and Hurricanes Harvey, Irma, and Maria. To assess flood risk across coastal landscapes, it is advantageous to first delineate flood transition zones, which we define as areas susceptible to hydrologic and coastal flooding and their collective interaction. We utilize numerical simulations combining rainfall excess and storm surge for the 2016 Louisiana flood to describe a flood transition zone for southeastern Louisiana. We show that the interaction of rainfall excess with coastal surge is nonlinear and less than the superposition of their individual components. Our analysis provides a foundation to define flooding zones across coastal landscapes throughout the world to support flood risk assessments.

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Dec 05

Publication | Astronomic tides and nonlinear tidal dispersion for a tropical coastal estuary with engineered features (causeways): Indian River Lagoon

IRL_EnergyDissipationM.V. Bilskie, P. Bacopoulos, S.C. Hagen (2017). “Astronomic tides and nonlinear tidal dispersion for a tropical coastal estuary with engineered features (causeways): Indian River Lagoon.” Estuarine, Coastal, and Shelf Science. In Press. doi: 10.1016/j.ecss.2017.11.009

Abstract Astronomic tides and nonlinear tidal dispersion were assessed for the Indian River lagoon system, a tropical coastal estuary (located in central east Florida) with engineered features (causeways). The four inlets, which choke the tides entering the system, together with the expansive size and shallowness of the estuary (and the associated energy dissipation) are the prominent mechanisms leading to the microtidal environment of the lagoon. Inside the shallows, there are 12 causeway abutments that cause a compartmentalization of the waters into separate basins, whereby the causeway openings act mechanistically as acceleration-inducing throttles to promote local regions of high kinetic energy (velocities). The causeways lead to a furthered decay of tidal amplitudes, phase lags in the tides and an enhanced generation of harmonic overtides and tidal residuals relative to the natural domain (i.e., fully open—no causeways). Numerical modeling of astronomic tidal flows (Advanced Circulation—ADCIRC) employed an unstructured, triangular mesh that resolved the entire scale of the lagoonal system with element sizes of 10–100 m and captured its many intricate domain features, including: the causeways in Indian River lagoon proper and Banana River lagoon; over 150 km of sinuous channels in Mosquito lagoon; and the hydraulic connections of the individual lagoons—one of which, Haulover Canal, is only 55 m wide. The model performed well with an index of agreement of (on average) 94% when compared with tidal data from 23 stations located throughout the system. Tides in the shallows are small at just millimeters in range; the model captured the tidal signal at the stations located there with an index of agreement of (at worst) 79%. Considering previous tidal studies of the Indian River lagoon system and tropical coastal estuaries in general, this level of domain definition and model validation of astronomic tide behavior is unprecedented and provides a benchmark for numerical simulation of lagoonal tidal flow.

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Sep 27

Coupling Hydrologic, Tide and Surge Processes to Enhance Flood Risk Assessments for the Louisiana Coastal Master Plan

Flood risk at the coastal land margin is influenced by both hydrologic and tidal processes, especially in deltaic flood plains, which leads to the realization that there exist transitional zones of flood hazard and risk. This coastal flood plain phenomena will be better understood by delineating dominant contributors to flood hazard and risk as they move from surge-only (in the immediate coastal flood zone) to hydrologic and tidal (including both low impact, high frequency events such as winter storms and higher impact lower frequency events such as storm surge) to rainfall-induced-only further from the coast. The intent of the proposed efforts are to demonstrate that while this transitional flood risk zone retreats towards populated areas with coastal land loss, it can also be advanced away from urban centers with the aid of Louisiana Coastal Master Plan projects. To do so will directly address the Rationale from Topic 6: “The Coastal Master Plan recognizes the importance of both future climate change and episodic forcing, such as storms and droughts, in shaping the future of the coast and the success of protection and restoration projects.” The aim of the proposed research is to address these fundamental issues by defining regions where both rainfall runoff and storm surge (both winter and tropical storms) overlap through development of a coupled hydrologic and hydrodynamic model to enable more comprehensive enhanced flood risk assessments and more.

“Coupling Hydrologic, Tide and Surge Processes to Enhance Flood Risk Assessments for the Louisiana Coastal Master Plan.” The Water Institute of the Gulf, Restore Act Center of Excellence for Louisiana, 01/25/2017, $499,882 (PI: S.C. Hagen), Role: Co-PI

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Aug 25

Systems Approaches for Coastal Hazard Assessment and Resilience

S.C. Hagen, D.L. Passeri, M.V. Bilskie, D.E. DeLorme, D. Yaskowitz (2017). “Systems Approaches for Coastal Hazard Assessment and Resilience.” Oxford Research Encyclopedia of Natural Hazard Science. DOI:10.1093/acrefore/9780199389407.013.28

The framework presented herein supports a changing paradigm in the approaches used by coastal researchers, engineers, and social scientists to model the impacts of climate change and sea level rise (SLR) in particular along low-gradient coastal landscapes. Use of a System of Systems (SoS) approach to the coastal dynamics of SLR is encouraged to capture the nonlinear feedbacks and dynamic responses of the bio-geo-physical coastal environment to SLR, while assessing the social, economic, and ecologic impacts. The SoS approach divides the coastal environment into smaller subsystems such as morphology, ecology, and hydrodynamics. Integrated models are used to assess the dynamic responses of subsystems to SLR; these models account for complex interactions and feedbacks among individual systems, which provides a more comprehensive evaluation of the future of the coastal system as a whole. Results from the integrated models can be used to inform economic services valuations, in which economic activity is connected back to bio-geo-physical changes in the environment due to SLR by identifying changes in the coastal subsystems, linking them to the understanding of the economic system and assessing the direct and indirect impacts to the economy. These assessments can be translated from scientific data to application through various stakeholder engagement mechanisms, which provide useful feedback for accountability as well as benchmarks and diagnostic insights for future planning. This allows regional and local coastal managers to create more comprehensive policies to reduce the risks associated with future SLR and enhance coastal resilience.

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Nov 14

Publication | Coastal wetland response to sea-level rise in a fluvial estuarine system

alizad-biomassK. Alizad, S.C. Hagen, J.T. Morris, S.C. Medeiros, M.V. Bilskie, J.F. Weishampel (2016). “Coastal wetland response to sea-level rise in a fluvial estuarine system.” Earth’s Future. In-Press.


Abstract 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.

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