Complexities in barrier island response to sea level rise : insights from numerical model experiments, North Carolina Outer Banks

Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): F03004, doi:10.1029/2009JF001299.Using a morphological-behavior model to conduct sensitivity experiments, we investigate the sea level rise response of a complex coastal environment to changes in a variety of factors. Experiments reveal that substrate composition, followed in rank order by substrate slope, sea level rise rate, and sediment supply rate, are the most important factors in determining barrier island response to sea level rise. We find that geomorphic threshold crossing, defined as a change in state (e.g., from landward migrating to drowning) that is irreversible over decadal to millennial time scales, is most likely to occur in muddy coastal systems where the combination of substrate composition, depth-dependent limitations on shoreface response rates, and substrate erodibility may prevent sand from being liberated rapidly enough, or in sufficient quantity, to maintain a subaerial barrier. Analyses indicate that factors affecting sediment availability such as low substrate sand proportions and high sediment loss rates cause a barrier to migrate landward along a trajectory having a lower slope than average barrier island slope, thereby defining an “effective” barrier island slope. Other factors being equal, such barriers will tend to be smaller and associated with a more deeply incised shoreface, thereby requiring less migration per sea level rise increment to liberate sufficient sand to maintain subaerial exposure than larger, less incised barriers. As a result, the evolution of larger/less incised barriers is more likely to be limited by shoreface erosion rates or substrate erodibility making them more prone to disintegration related to increasing sea level rise rates than smaller/more incised barriers. Thus, the small/deeply incised North Carolina barriers are likely to persist in the near term (although their long-term fate is less certain because of the low substrate slopes that will soon be encountered). In aggregate, results point to the importance of system history (e.g., previous slopes, sediment budgets, etc.) in determining migration trajectories and therefore how a barrier island will respond to sea level rise. Although simple analytical calculations may predict barrier response in simplified coastal environments (e.g., constant slope, constant sea level rise rate, etc.), our model experiments demonstrate that morphological-behavior modeling is necessary to provide critical insights regarding changes that may occur in environments having complex geometries, especially when multiple parameters change simultaneously.This work was partially supported by the U.S. Geological Survey, Woods Hole Science Center and a sabbatical leave fellowship from Oberlin College to Laura Moore from the Mellon‐8 Consortium

High-angle wave instability and emergent shoreline shapes : 2. Wave climate analysis and comparisons to nature

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): F04012, doi:10.1029/2005JF000423.Recent research has revealed that the plan view evolution of a coast due to gradients in alongshore sediment transport is highly dependant upon the angles at which waves approach the shore, giving rise to an instability in shoreline shape that can generate different types of naturally occurring coastal landforms, including capes, flying spits, and alongshore sand waves. This instability merely requires that alongshore sediment flux is maximized for a given deepwater wave angle, a maximum that occurs between 35° and 50° for several common alongshore sediment transport formulae. Here we introduce metrics that sum over records of wave data to quantify the long-term stability of wave climates and to investigate how wave climates change along a coast. For Long Point, a flying spit on the north shore of Lake Erie, Canada, wave climate metrics suggest that unstable waves have shaped the spit and, furthermore, that smaller-scale alongshore sand waves occur along the spit at the same locations where the wave climate becomes unstable. A shoreline aligned along the trend of the Carolina Capes, United States, would be dominated by high-angle waves; numerical simulations driven by a comparable wave climate develop a similarly shaped cuspate coast. Local wave climates along these simulated capes and the Carolina Capes show similar trends: Shoreline reorientation and shadowing from neighboring capes causes most of the coast to experience locally stable wave climates despite regional instability.This research was funded by the Andrew W. Mellon Foundation and NSF grants DEB-05-07987 and EAR-04-44792

High-angle wave instability and emergent shoreline shapes : 1. Modeling of sand waves, flying spits, and capes

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): F04011, doi:10.1029/2005JF000422.Contrary to traditional findings, the deepwater angle of wave approach strongly affects plan view coastal evolution, giving rise to an antidiffusional “high wave angle” instability for sufficiently oblique deepwater waves (with angles between wave crests and the shoreline trend larger than the value that maximizes alongshore sediment transport, ∼45°). A one-contour-line numerical model shows that a predominance of high-angle waves can cause a shoreline to self-organize into regular, quasiperiodic shapes similar to those found along many natural coasts at scales ranging from kilometers to hundreds of kilometers. The numerical model has been updated from a previous version to include a formulation for the widening of an overly thin barrier by the process of barrier overwash, which is assumed to maintain a minimum barrier width. Systematic analysis shows that the wave climate determines the form of coastal response. For nearly symmetric wave climates (small net alongshore sediment transport), cuspate coasts develop that exhibit increasing relative cross-shore amplitude and pointier tips as the proportion of high-angle waves is increased. For asymmetrical wave climates, shoreline features migrate in the downdrift direction, either as subtle alongshore sand waves or as offshore-extending “flying spits,” depending on the proportion of high-angle waves. Numerical analyses further show that the rate that the alongshore scale of model features increases through merging follows a diffusional temporal scale over several orders of magnitude, a rate that is insensitive to the proportion of high-angle waves. The proportion of high-angle waves determines the offshore versus alongshore aspect ratio of self-organized shoreline undulations.This research was funded by the Andrew W. Mellon Foundation and NSF grants DEB-05-07987 and EAR-04-44792

Geographies of Resettlement in the United States

1. The United States Refugee Resettlement Program Officially established and standardised in 1980, the United States Refugee Admissions Program (USRAP) has historically been the largest resettlement programme in the world, until it was surpassed in 2018 for the first time by Canada, as a result of drastic programme cuts under the Trump administration. The resettlement system can be understood as a public-private partnership, wherein initial processing is done at the national level, but the pr..

Conclusion

1. Main findings This paper has explored the interrelation between refugee resettlement and urban development in the case study of Buffalo, NY. Particular attention on the neighbourhood of the Lower West Side has allowed for a more detailed understanding of this intersection. It builds on the small body of literature that bridges the gap between work on urban restructuring and refugee resettlement, to ask: in the context of urban restructuring, what role does ‘the resettled refugee’ play? Thr..

Interviews and media review – recognising opportunities, challenges and complexities

1. Sources Taking into account the development efforts and visible changes to the city of Buffalo described in Chapter 6, this section draws on additional sources to explore more deeply the discussion around this development. The author reviewed articles tagged ‘refugee’ in the ‘local’ section of the Buffalo News from the years 2008 to 2021. Quotes sourced from local leaders in regional and national newspapers lend further perspective to the narrative and discursive practices of stakeholders ..

Methodology

1. Case study method and scale The phenomenon of rising resettlement paired with urban redevelopment has been identified in multiple regions and nations, allowing for analysis of regional trends (Bose, 2020; Pottie-Sherman, 2020), as well as a handful of case studies (Housel et al., 2018; Adelman et al., 2019; Shrider et al., 2018). For this project, a case study approach was chosen to address this phenomenon. This is because the particularities of each urban context may reveal different as..

Where Goes the Neighbourhood?

This paper explores the intersection of urban restructuring and refugee resettlement. Centring around a case study of Buffalo, New York (NY), USA, it adds to the small but growing number of studies on resettlement in post-industrial contexts. Buffalo is experiencing economic and population growth, termed by some as the city’s renaissance (even the refugee renaissance), while others regard it as gentrification and exclusionary development. At the same time, the city has become one of the largest resettlement sites in the country. In politicians’ statements and the media, refugees are credited with being one of the key drivers for this development in the city. Through interviews with various stakeholders, I explore how these phenomena are understood. I argue that this convening of factors creates a particular conception of the figure of the resettled refugee. In Buffalo, refugees emerge as a particularly valued form of other, capable of driving development in a way that fits ideally within the narrative of ‘rust to reinvention’. As such, they become outside economic development agents, divorced from the challenges faced by struggling residents for decades. Resettlement actors navigate this conversation, recognising the challenges faced by refugees and other residents, while at the same time carrying forward prevailing narratives and frames. We extend our heartfelt thanks to the Vahabzadeh Foundation for financially supporting the publication of best works by young researchers of the Graduate Institute, giving a priority to those who have been awarded academic prizes for their master’s dissertations