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Replenishing Delaware's beaches in the face of ongoing erosion, sea level rise

A picture of the Bethany Beach boardwalk, taken after a March 2018 nor'easter.

Faced with rising seas and constant beach erosion, Delaware's beaches may need more than just replenishment in the future.



The U.S. Army Corps of Engineers says Delaware beaches get renourished every three to four years based on data showing how quickly shorelines erode.


Randy Wise, a coastal engineer with the Army Corps Philadelphia District, says staff consider sea level rise as they develop projects, noting that as sea levels rise, there will be more erosion.


But he says that does not mean they'll have to spend more money to renourish beaches more frequently.


"Over the design life of the project, we can basically build into our future designs to accommodate that erosion without the need to reduce the renourishment cycle," Wise said.


The corps analyzes beach renourishment projects in 50-year periods, meaning it has not yet planned past 2100 — when 8 to 10 percent of Delaware could be inundated by sea level rise, according to a Delaware Coastal Programs' vulnerability assessment.


"If sea level rise really is as great as some scientists think it might be, we would have to relook at and revisit in the future, our projects, and make a reassessment as to whether or not they would perform and how we would account for that accelerated sea level rise if it occurs," Wise said.


The current model of pumping sand from the bottom of the ocean and onto beaches every three to four years is a temporary, costly solution for an ongoing problem, University of Delaware oceanography professor Art Trembanis said.


"It’s as if the wound keeps opening all the time and all we’re doing is changing out the Band-aid over it," Trembanis said. "A good physician or good doctor would say ‘hang on, let's stop and try to address the underlying cause of it'."


According to data Trembanis collected, Delaware beaches have collectively received more than 25 million cubic yards of sand since 1962.


"And over the time as we’ve had to continue nourishing, sea levels have been seemingly increasingly rising," Trembanis said. "That means we’ll expect to have to put as much or more sand on our beaches."


But sand supply is limited, he said.


Bethany, South Bethany and Fenwick Island are getting beach replenishment this summer.


These beaches last got more sand in 2013. Current renourishment work was delayed due to equipment availability.


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