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Council hears Boothroyd’s talk on rising sea level

August 2, 2013

Aerial view of damage done to Charlestown Beach after Superstorm Sandy passed through. (Chariho Times File Photo)

CHARLESTOWN – Future major storms combined with sea level rise are a “very large problem,” especially in coastal communities, like Charlestown, Dr. Jon C. Boothroyd told the Charlestown Town Council during a workshop Monday.

Boothroyd, a member of the Rhode Island Geological Survey and a professor emeritus of geology at the University of Rhode Island, discussed the Coastal Resources Management Council’s recently implemented Beach Special Area Management Plan and new data about sea level rise, inundation and storm surge that may impact Charlestown.
Boothroyd said CRMC is planning for a 3-foot to 5-foot sea level rise by 2100 and a 1.5-foot rise by 2050.
“It may not happen exactly in that order, and that is actually an accelerated sea level rise,” Boothroyd said. “If it kept rising at the present day rate, it wouldn’t reach that high.”
Approximately 26,000 years ago, there was glacier ice all the way out to Block Island and sea level was about 450 feet or 120 meters below the present level, according to Boothroyd.
About 21,300 years ago, the ice began melting and while there was still ice in Narragansett Bay and the Block Island and Rhode Island glacial lakes, sea level began to rise.
After several thousand years of melting, about 8,000 years ago, most of the ice was melted and the rate of sea level rise began to slow.
Today, carbon dioxide levels rising in the atmosphere and have reached 399 parts per million, higher than levels over the past 650,000 years. The increase in carbon dioxide causes the atmosphere to warm up, ice to melt (such as off the glaciers in Greenland) and sea level to rise.
With higher sea levels, storm surge becomes greater causing more inundation and more damage.
According to Boothroyd, Superstorm Sandy caused the most damage to Charlestown beaches since 1954.
“Rhode Island received a glancing blow,” Boothroyd said. “But it is a public misconception that it was a 100-year event.”
Boothroyd said it was a “20-year to 30-year event” in Narragansett and a “40-year event” in Misquamicut. Of course, the storm was even more severe on Long Island and in New Jersey.
Boothroyd said Charlestown Beach has eroded 147 feet between 1939 and 2004 and has eroded even further since Sandy.
With all the sand getting pushed back due to wave action from storms, Boothroyd said the barrier is migrating back.
“My message is to leave the sand here,” he said. “Once you remove the sand, it creates a surge channel. If you left it, the water wouldn’t get back there as easily. You could compact it and put a little gravel on it.”
Boothroyd said this is especially true of the Quonochontaug barrier.
“Removal is a bad idea,” he said. “Barriers naturally retreat landward and upward. As it moves upward, it’s better able to absorb the energy of the next storm. We have to figure out a way to have people occupying that space to live with that, it’s called resiliency.”
While Boothroyd suggests letting the sand naturally migrate “landward and upward” he also discussed the use of hardened structures to prevent erosion.
“Some sea walls do work well, and they will be there forever,” he said. “But you have to decide whether you want it to be there or not.”
Boothroyd used Galveston, Texas as an example, where there is an effective sea wall but only a narrow stretch of rocky beach.
The Beach SAMP will experiment with different types of structures in Matunuck and Misquamicut in an effort to determine which, if any, will best combat erosion.
“I wish we could find something,” Boothroyd said. “It has to be porous enough to allow sand through but attenuate wave action. I can tell you a lot of things that don’t work, but I haven’t found a thing that does work.”
When asked what to do until a solution is found, Boothroyd replied, “What’s the thing to do? Well, it’s elevate and move back a far as you can and I know that’s a tough thing for people.”
To view Boothroyd’s complete lecture, visit www.charlestownri.org and follow the links to ClerkBase. To learn more about Beach SAMP www.beachsamp.org.

Source 
Southern Rhode Island Newspapers
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