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Saturday, August 25, 2012

When ocean and humans collide

Storm surge during the great Blizzard of '78
By KEVIN PROFT/ News staff
NARRAGANSETT — Rhode Island’s coastline is in a natural and constant state of flux. The coastline is altered most during big storms such as hurricanes and nor’easters. High waves wash away or damage dunes that protect land further inland. They also pound sea cliffs saturated and weakened by rain, causing sections to collapse. 

Watching Blue Shutters getting eaten from waves caused by a
near pass of one of last year's hurricanes
Narrow barrier beaches, such as Ninigret Beach in Charlestown, can dramatically shift position.

If humans weren’t part of the equation, this information would be no cause for alarm. Dunes would recover, debris from cliff walls would slowly erode to sand, and reoriented barrier beaches would continue to protect wetlands and the mainland from the unrelenting ocean. But, when humans interact with the shoreline and alter it in a fundamental way, coastal residents often experience alarmingly problematic effects.
Matunuck is the Ocean State’s best example of what happens when ocean and human development collide. Matunuck’s eroding coast is threatening to undercut Matunuck Beach Road and leave 1,600 homes and businesses with no way to enter or leave the community. To prevent the road from being destroyed, which would create a clear public safety issue, a 220-foot sheet-pile wall will be built in September to hold back the ocean.
At best, this is a temporary and localized solution to a much bigger problem. It doesn’t prevent beachside establishments such as Ocean Mist from being overtaken by the ocean, and it doesn’t halt erosion in areas not protected by the wall — it has even been postulated that hardened shorelines cause neighboring natural shorelines to erode faster.
This sheet-pile wall also doesn’t address the fact that erosion is happening elsewhere in Rhode Island. A residence on the barrier beach in Green Hill that was protected by a dune and a wide beach in 1980 had to be moved back after the Patriots’ Day storm of 2007 when it was flooded by the ocean. The process included segmenting the house and relocating it by crane.
These issues, along with explanations of why erosion happens and how Rhode Islanders should confront the consequences, were the topic of a recent lecture given by Janet Freedman, a geologist for the Coastal Resources Management Council (CRMC), at the University of Rhode Island Graduate School of Oceanography.
Rhode Island is especially susceptible to coastal erosion because more than 50 percent of the state’s coast is made of rock and sediment that is easily eroded, according to Freedman. During storms, the combination of storm surge — naturally higher ocean levels created when hurricane winds push water toward the shore — and bigger waves allow water to penetrate further inland or lash with more force against dunes and cliffs. Higher sea levels mean more erosion during storms. Heavy rains during storms also cause slopes to become oversaturated and more likely to fail.
This helps explain why coastal erosion is accelerating. Today, according to Freedman, sea levels are about 3 inches higher than they were in 1991 and are conservatively expected to reach 5 feet higher by 2100. Freedman said parts of Westerly are already experiencing daily flooding at high tide during the spring, when tides reach their peak height. Those additional 3 inches get added to the ocean’s height during a storm and translates into more intense erosion.
In addition to sea level rise, climate change is generating more frequent and intense storms. Since most erosion occurs during intense storms, the predictable effect has been more rapidly retreating coastlines.
To combat the effects of coastal erosion, CRMC is developing an Erosion and Inundation Special Area Management Plan. The plan will rely on science-based data from studies scheduled to happen at multiple sites around the state where coastal erosion is occurring.
Experimental erosion control areas have been created to test different strategies related to controlling erosion, such as geo-mattresses and wave attenuators. Successful strategies can then be implemented in similar situations elsewhere in the state, according to CRMC.
Erosion is a natural process, but humans are exacerbating it. Short-sighted development, rising sea levels and more frequent and intense storms have resulted in unforeseen effects that need to be dealt with sooner rather than later if responsible solutions are to be implemented.