Wave forecasting and longshore sediment transport gradients along a transgressive barrier island: Chandeleur Islands,Louisiana |
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Authors: | Ioannis Y Georgiou Jennifer K Schindler |
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Institution: | 1.Department of Earth and Environmental Sciences, Pontchartrain Institute for Environmental Sciences,University of New Orleans,New Orleans,USA |
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Abstract: | Louisiana barrier islands, such as the chain surrounding the southeast region of the state, are experiencing rapid loss of
land area, shoreline erosion, and landward migration due to transgression and in-place drowning, and the landfall of several
major hurricanes in the last decade. Observations of migration rates and overall impacts to these barrier islands are poorly
understood since they do not respond in a traditional way, such as barrier rollover. This paper aims to verify how wave energy
and potential longshore sediment transport trends have influenced the recent evolution of the Chandeleur Islands, by direct
comparison with recent observations of migration and erosion trends. The Chandeleur Islands are characterized by a bidirectional
transport system, with material moving from the central arc to the flanks. The longshore sediment transport along the barrier
islands was calculated after propagation and transformation of waves to breaking (generated using observed winds), and through
the use of a common longshore sediment transport formula. Seasonal variations in wind climate produced changes in the transport
trends and gradients that agree with migration and rotation patterns observed for this barrier island system. Results suggest
that wind dominance produces seasonal oscillations that cause an imbalance in the resulting transport gradients that over
time are responsible for higher rates of transport in the northward direction. These results and data from other works verify
the evolutionary model previously suggested, and qualitatively confirm the recent observations in asymmetric shoreline erosion. |
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