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Two meters of dune lost at one site and almost nothing at another two miles away — and the difference was not the storm.
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Surveys carried out after the January storm found shoreline response varying by an order of magnitude between sites less than two miles apart, with one profile losing roughly two meters of dune face and another almost none.
Both sites experienced the same wave conditions and the same surge. The difference, according to Tobias Wren, is what was available to lose.
"The site that held has a sediment supply and the site that did not has been cut off from one for thirty years," he said. "The storm is the trigger. The budget is the explanation."
Students in GEOL 330 Coastal Geomorphology carried out the profile surveys as part of coursework, repeating a set of transects that have been measured after significant storms since 2016. The repeat-survey record is what makes the comparison possible.
Daniel Okonkwo, who works on coastal protection design, said the result is a familiar and inconvenient one for engineering practice. "A protection scheme upcoast holds that shoreline and starves the one below it. Everyone knows this. It is very hard to price and it is usually somebody else's jurisdiction."
The surveyed transects will be re-measured in the spring to record how much of the lost material returns, which at the starved site is expected to be very little.
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