Estimating Coastal Dune Vulnerability to Storm Sequences: A Pilot Study

Authors: Hayley Springer*, University of Alabama, Ian Walker, Arizona State University , Douglas Sherman, University of Alabama
Topics: Coastal and Marine, Geomorphology
Keywords: Coastal Geomorphology, Storm Sequences, Dunes
Session Type: Illustrated Paper
Day: 4/12/2018
Start / End Time: 5:20 PM / 7:00 PM
Room: Canal St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

In many coastal jurisdictions dunes have become the preferred means of protection against erosion, storm surge, and inundation associated with a 100-year storm event. Depending on the environment, this leads to specifications for ideal dune volume and crest elevation to provide this function. This approach does not recognize the potential for substantial dune erosion associated with sequences of lesser storms at intervals that are short relative to the natural recovery time of the dune. Consecutive storm events can result in the dune system being progressively eroded before full recovery from a previous event. We tested this concept using times series of wave data and beach profiles applied to a stretch of the North Carolina coast at Pine Island. Wave data, from the European Center for Medium-Range Weather Forecasts (ECMWF) are available from 1901-2010 and we used North American Regional Reanalysis data to extend the time series to 2016. Events were defined as having a wave height of 4m or greater for a duration of at least 18 hours. These data were used to estimate storm recurrence intervals. Beach response was based on finding dune response thresholds according to the profile (1981-2017) and LiDAR data (2013-2017), and linking the magnitude of erosion to events of known magnitudes. Storm sequences with events likely to cause substantial loss of dune height or volume within a time frame less than expected recovery time are identified, and the probability of such sequences are estimated for the future.

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