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CHARLESTOWN â€“ Future major storms combined with sea level rise are a â€śvery large problem,â€ť 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 Councilâ€™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.
â€śIt may not happen exactly in that order, and that is actually an accelerated sea level rise,â€ť Boothroyd said. â€śIf it kept rising at the present day rate, it wouldnâ€™t reach that high.â€ť
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.
â€śRhode Island received a glancing blow,â€ť Boothroyd said. â€śBut it is a public misconception that it was a 100-year event.â€ť
Boothroyd said it was a â€ś20-year to 30-year eventâ€ť in Narragansett and a â€ś40-year eventâ€ť 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.
â€śMy message is to leave the sand here,â€ť he said. â€śOnce you remove the sand, it creates a surge channel. If you left it, the water wouldnâ€™t get back there as easily. You could compact it and put a little gravel on it.â€ť
Boothroyd said this is especially true of the Quonochontaug barrier.
â€śRemoval is a bad idea,â€ť he said. â€śBarriers naturally retreat landward and upward. As it moves upward, itâ€™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, itâ€™s called resiliency.â€ť
While Boothroyd suggests letting the sand naturally migrate â€ślandward and upwardâ€ť he also discussed the use of hardened structures to prevent erosion.
â€śSome sea walls do work well, and they will be there forever,â€ť he said. â€śBut you have to decide whether you want it to be there or not.â€ť
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.
â€śI wish we could find something,â€ť Boothroyd said. â€śIt has to be porous enough to allow sand through but attenuate wave action. I can tell you a lot of things that donâ€™t work, but I havenâ€™t found a thing that does work.â€ť
When asked what to do until a solution is found, Boothroyd replied, â€śWhatâ€™s the thing to do? Well, itâ€™s elevate and move back a far as you can and I know thatâ€™s a tough thing for people.â€ť
To view Boothroydâ€™s complete lecture, visit www.charlestownri.org and follow the links to ClerkBase. To learn more about Beach SAMP www.beachsamp.org.