Browsing by Subject "coastal processes"
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Item Open Access Convexity, Concavity, and Human Agency in Large-scale Coastline Evolution(2014) Ells, Kenneth DanielCoherent, large-scale shapes and patterns are evident in many landscapes, and evolve according to climate and hydrological forces. For large-scale, sandy coastlines, these shapes depend on wave climate forcing. The wave climate is influenced by storm patterns, which are expected to change with the warming climate, and the associated changes in coastline shape are likely to increase rates of shoreline change in many places. Humans have historically responded to coastline change by manipulating various coastal processes, consequently affecting long-term, large-scale coastline shape change. Especially in the context of changing climate forcing and increasing human presence on the coast, the interaction of the human and climate-driven components of large-scale coastline evolution are becoming increasingly intertwined.
This dissertation explores how climate shapes coastlines, and how the effects of humans altering the landscape interact with the effects of a changing climate. Because the coastline is a spatially extended, nonlinear system, I use a simple numerical modeling approach to gain a basic theoretical understanding of its dynamics, incorporating simplified representations of the human components of coastline change in a previously developed model for the physical system.
Chapter 1 addresses how local shoreline stabilization affects the large scale morphology of a cuspate-cape type of coastline, and associated large-scale patterns of shoreline change, in the context of changing wave climate, comparing two fundamentally different approaches to shoreline stabilization: beach nourishment (in which sediment is added to a coastline at a long-term rate that counteracts the background erosion), and hard structures (including seawalls and groynes). The results show that although both approaches have surprisingly long-range effects with spatially heterogeneous distributions, the pattern of shoreline changes attributable to a single local stabilization effort contrast greatly, with nourishment producing less erosion when the stabilization-related shoreline change is summed alongshore.
Chapter 2 presents new basic understanding of the dynamics that produce a contrasting coastline type: convex headland-spit systems. Results show that the coastline shapes and spatially-uniform erosion rates emerge from two way influences between the headland and spit components, and how these interactions are mediated by wave climate, and the alongshore scale of the system. Chapter 2 also shows that one type of wave-climate change (altering the proportion of `high-angle' waves) leads to changes in coastline shape, while another type (altering wave-climate asymmetry) tends to reorient a coastline while preserving its shape.
Chapter 3 builds on chapter 2, by adding the effects of human shoreline stabilization along such a convex coastline. Results show that in the context of increasing costs for stabilization, abandonment of shoreline stabilization at one location triggers a cascade of abandonments and associated coastline-shape changes, and that both the qualitative spatial patterns and alongshore speed of the propagating cascades depends on the relationship between patterns of economic heterogeneity and the asymmetry of the wave-climate change--although alterations to the proportion of high-angle waves in the climate only affects the time scales for coupled morphologic/economic cascades.
Item Open Access Examining the Effects of Changing Coastline Processes on Hawksbill Sea Turtle (Eretmochelys imbricata) Nesting Habitat(2009-04-23T21:50:11Z) Varela-Acevedo, EldaHawksbill sea turtles (Eretmochelys imbricata) are severely depleted in the Wider Caribbean Region due to over-exploitation, as well as habitat loss and degradation. Hawksbills typically rely on narrow, steeply sloping beach strands for successful reproduction, making them potentially vulnerable to sea level rise, stronger storm cycles, and widespread coastal erosion predicted to accompany contemporary models of global climate change. In response to the need for easy-to-use methods in understanding how climate change will affect coastlines, and specifically how such change will affect wildlife habitats in coastal areas, a “Sea Turtle Nesting Beach Characterization Manual” was created using hawksbill turtles as a model. Some of the features considered in the Manual were beach width, vegetation, lighting, sediment type and predation. While providing useful data on coastline change over time, the Manual also serves as an educational tool to help residents and property owners understand how environmental change may influence the inhabitability of coastline areas for endangered species such as sea turtles. This report demonstrates the Manual’s usefulness in evaluating habitat suitability for hawksbill nesting and vulnerability to climate change in Barbados, one of the Caribbean’s largest hawksbill rookeries. The Manual itself will undergo international peer-review and be published separately.