Evaluation of Coastal Highway Vulnerability Indicators: NC

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EVALUATION OF COASTAL HIGHWAY VULNERABILITY INDICATORS: NC 12, RODANTHE, NC
Elizabeth J. Sciaudone, Ph.D., P.E. and Margery F. Overton, Ph.D.
North Carolina State University
Department of Civil, Construction, and Environmental Engineering
Box 7908, Raleigh NC 27695-7908
[email protected]
As part of a coastal monitoring program initiated in 2010, researchers at North Carolina State
University have been monitoring the barrier island surrounding the coastal highway NC 12 from
Oregon Inlet to the town of Rodanthe. The goal of this monitoring effort is to identify
vulnerable areas of highway to assist with future transportation planning efforts. A number of
indicators are employed to assess vulnerability, including road proximity to shoreline, barrier
island width, dune crest elevation, road elevation, beach width, historic erosion rate, and beach
volume seaward of the road.
To date, two severe storms have impacted the area: Hurricane Irene in 2011, and Hurricane
Sandy in 2012. After Hurricane Irene in 2011, the highway was breached in two locations: one
along Pea Island often referred to as “New New Inlet,” and one at the north end of the town of
Rodanthe (Figure 1). In Rodanthe, breaching occurred from the sound side as water elevation
rose and soundside surge was conveyed along existing channels to the road, where it broke
through narrow dunes and traveled along existing roads and driveways. The breach was filled
after the storm, repairs were made to the road, and sandbag-reinforced dunes were
constructed seaward of the highway. The same area was overwashed during Hurricane Sandy in
2012, causing additional damage to the road and dunes.
This presentation will evaluate the effectiveness of the vulnerability indicators in predicting
storm damage to the road. Some indicators are more effective than others in predicting
soundside breaching and others more effective in predicting oceanside damage, as expected. In
general for ocean overwash it is important to consider not only road proximity to shoreline but
also dune height, dune proximity to shoreline, and dune volume to evaluate storm resistance.
Soundside vulnerability is a combination of low oceanside dunes and existing channels that can
convey water quickly across the barrier island.
Figure 1. Rodanthe breach area on 8-2-11 and post-storm 8-28-11.
Author Bio:
Elizabeth Sciaudone is a Teaching Assistant Professor in the Department of Civil, Construction,
and Environmental Engineering at North Carolina State University. She teaches courses on fluid
mechanics and coastal engineering and conducts research on coastal hazards identification and
vulnerability analysis. Additionally, she works as Managing Editor of the ASBPA journal, Shore &
Beach.
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