38 Past and Future Coastal Evolution in Response to Sea-Level Changes and Storm Impacts (Posters)

Friday, 29 March 2019
1:00 PM - 5:00 PM
Carolina Ballroom

SHORT-TERM PATTERNS OF POST-STORM RECOVERY ON AN UNDEVELOPED BARRIER ISLAND: HURRICANE FLORENCE AND MASONBORO ISLAND, NC

Paper number: 38-10
Program: Theme Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

Hurricane Florence made landfall as a Category 1 storm on September 14, 2018 near Wrightsville Beach, NC. The storm produced 5 m waves and water levels 1.2 m above predicted tide. On Masonboro Island, an undeveloped, N/S trending barrier island located immediately south of Wrightsville Beach, the combination of storm surge and waves resulted in extensive dune breaching and overwash, especially along the southern half of the island. Fan deposits as much as 80 cm thick overtopped pre-existing dune, back-barrier flat, and tidal marsh environments, which caused an overall flattening of the cross-shore profile. The storm also produced extensive overwash channels that ranged in depth from 8 to 20 cm, and extended to the marsh and back-barrier lagoon. Many of these channels remained active during high tide for more than a month after the storm, resulting in the redistribution of finer grained sediment to the back-barrier, and the landward growth of the visible fan edge. Continued post-storm reworking also resulted in the smoothing of storm-generated microtopography, including overwash channels and the landward edges of the overwash lobes. Cross-shore profiles also reveal an increase in elevation post-storm, indicative of a gradual return to pre-storm conditions. These geomorphological changes are evident in Digital Terrain Models (DTMs), created from time series imagery collected by a senseFly eBee Plus Unmanned Aerial System (UAS) and processed in Pix4Dmapper, as well as terrestrial laser scans, collected with a Trimble SX10 and processed with Trimble Business Center, one month and three months post-storm. The observed geomorphic response of the island to Hurricane Florence is very similar to that of Hurricane Matthew (2016) several years prior, indicating these results are representative of the island’s response to storm events. Moreover, the observed timing and patterns of recovery processes on this undeveloped island have implications for steady state recovery dynamics of barrier islands on local and regional scales.

Geological Society of America Abstracts with Programs. Vol. 51, No. 3

doi: 10.1130/abs/2019SE-327481

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