United States. National Oceanic and Atmospheric Administration (Postdoctoral Fellowship Program)

Physically-based Assessment of Hurricane Surge Threat under Climate Change

The future of coastal wetlands and their ecological value depend on their capacity to adapt to the interacting effects of human impacts and sea-level rise. Even though extensive wetland loss due to submergence is a possible scenario, its magnitude is highly uncertain due to limited understanding of hydrodynamic and bio-geomorphic interactions over time. In particular, the effect of man-made drainage modifications on hydrodynamic attenuation and consequent wetland evolution is poorly understood. Predictions are further complicated by the presence of a number of vegetation types that change over time and also contribute to flow attenuation. Here, we show that flow attenuation affects wetland vegetation by modifying its wetting-drying regime and inundation depth, increasing its vulnerability to sea-level rise. Our simulations for an Australian subtropical wetland predict much faster wetland loss than commonly used models that do not consider flow attenuation. Predictions of coastal wetland response to sea-level rise often neglect attenuation effects due to vegetation and infrastructure. Here, the authors show that including attenuation effects improves prediction of wetland evolution and suggests increases in wetland vulnerability to sea-level rise.

/pdf/potential-increase-in-coastal-wetland-vulnerability-to-sea-50tfins96l.pdf

Potential increase in coastal wetland vulnerability to sea-level rise suggested by considering hydrodynamic attenuation effects

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.

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

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.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015EF000332

Tidal hydrodynamics under future sea level rise and coastal morphology in the Northern Gulf of Mexico

/pdf/a-review-of-machine-learning-applications-to-coastal-47b1uwyb0a.pdf

A review of machine learning applications to coastal sediment transport and morphodynamics

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 10 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.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015EF000347

H.F. Needham

Papers

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