Investigating the evolution and formation of coastlines and the response to sea-level rise Ortiz, Alejandra C. 2015-10-09T14:33:19Z 2015-10-09T14:33:19Z 2015-09
dc.description Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2015 en_US
dc.description.abstract To understand how waves and sea level shape sandy shoreline profiles, I use existing energetics-based equations of cross-shore sediment flux to describe shoreface evolution and equilibrium profiles, utilizing linear Airy wave theory instead of shallow-water wave assumptions. By calculating a depth-dependent characteristic diffusivity timescale, I develop a morphodynamic depth of shoreface closure for a given time envelope, with depth increasing as temporal scale increases. To assess which wave events are most important in shaping the shoreface in terms of occurrence and severity, I calculate the characteristic effective wave conditions for both cross-shore and alongshore shoreline evolution. Extreme events are formative in the cross-shore shoreface evolution, while alongshore shoreline evolution scales linearly with the mean wave climate. Bimodal distributions of weighted wave heights are indicative of a site impacted more frequently by tropical storms rather than extra-tropical storms. To understand how offshore wave climate and underlying geometry of a carbonate reef platform shapes evolution of atolls, I simulate the hydrodynamics of a simplified reef flat, using XBeach, a two-dimensional model of infragravity wave propagation. The reef flat self-organizes to a specific width and water depth depending on the offshore wave climate and characteristics of the available sediment. Formation of a sub-aerial landmass, like a motu, can be initiated by a change in offshore wave climate (like a storm), which can create a nucleation site from mobilization and deposition of coarse sediment on the reef flat. Once a motu is present, the shoreline should prograde until reaching a critical reef-flat width. Our conceptual model of reef-flat evolution and motu formation is governed by understanding the hydrodynamics of the system and subsequent response of sediment transport. en_US
dc.description.sponsorship This research was supported by funding from Ocean Ventures Fellowship, Coastal Studies Institute, Geological Society of America Research Grant, DOD Strategic Environmental Research and Development Program Grant #RC-1701 and #RC-2336, National Science Foundation grant #CNH-0815875. en_US
dc.format.mimetype application/pdf
dc.identifier.citation Ortiz, A. C. (2015). Investigating the evolution and formation of coastlines and the response to sea-level rise [Doctoral thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution]. Woods Hole Open Access Server.
dc.identifier.doi 10.1575/1912/7563
dc.language.iso en_US en_US
dc.publisher Massachusetts Institute of Technology and Woods Hole Oceanographic Institution en_US
dc.relation.ispartofseries WHOI Theses en_US
dc.title Investigating the evolution and formation of coastlines and the response to sea-level rise en_US
dc.type Thesis en_US
dspace.entity.type Publication
relation.isAuthorOfPublication 64d306d5-9062-4814-80d9-dbdb794ce780
relation.isAuthorOfPublication.latestForDiscovery 64d306d5-9062-4814-80d9-dbdb794ce780
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