2012-08-30 / News

Beware coastal erosion

State geologist discusses the danger at URI lecture
BY MARGO SULLIVAN

For many Rhode Islanders, that famous picture of the summerhouse teetering on the rocks over Matunuck Beach sums up the threat from coastal erosion.

But less dramatic signs of erosion can be seen in almost every community on the state’s coast, according to Janet Freedman, geologist with the state’s Coastal Resources Management Council.

In Jamestown, the changes at Mackerel Beach could stand as an example of a shoreline shifting due to erosion, as the Conservation Commission has stated.

According to Freedman, coastal erosion is happening along shorelines worldwide. The situation is likely only to worsen with sea levels rising and other climate changes, she says.

Freedman addressed a packed house on Aug. 21 inside the Coastal Institute Auditorium at the University of Rhode Island’s Graduate School of Oceanography in Narragansett. Her presentation – “Losing Ground: Coastal Erosion in Rhode Island” – was the third and final event in this year’s R.I. Sea Grant lecture series.

In Matunuck, Freedman said, town officials are battling to protect a road, which provides access to residents and also carries a waterline feeding some 1,600 homes.

Despite the inevitability of the geological processes, state lawmakers have tasked the CRMC with studying options for shoreline communities. One Senate resolution charged the CRMC to address effects of erosion in Matunuck Village.

Because of this, some actions are being taken already to protect the coast. In Matunuck, town offi- cials have drawn up plans to build a sheet-pile wall to protect the road. The coastal council has approved the construction, Freedman said, but there are still a few tweaks.

The council also has identified some “experimental erosion control areas,” such as Misquamicut headland in Westerly. This beach has been diminished by overwash. Also, the CRMC is undertaking a comparative analysis of Rhode Island shorelines and making recommendations, she said. Finally, the enforcement issues are being studied.

Freedman said the management plan has three phases, starting with the area from Napatree Point in Westerly to Point Judith (including Block Island). The second phase, she said, deals with the east-facing Narragansett Bay shoreline, such as Aquidneck Island. Jamestown would be part of this phase. Finally, the last phase would encompass all the other bay areas.

Matunuck rates as one the state’s erosion “hot spots,” but it’s by no means the only place where the shore is moving inland, she said. Green Hill and Ninigret in Charlestown are also among the state’s hardest hit. And although Block Island’s cliffs would seem to afford protection against erosion, even the gigantic chunks of rock and sediment – known as slump blocks – have rolled down into the sea after heavy rainstorms.

Freedman showed slides of some erosion-control devices that have been used successfully in Rhode Island, but she noted they require constant maintenance. So far, the private property owners have footed the bill for the devices, such as coconut-fiber sandbags, which are sewn together and absorb the brunt of crashing waves. Other measures are riskier because the devices might break apart during a storm.

“Erosion happens in storms,” she said. Tropical storms and nor’easters are the prime threats, and they operate differently. The nor’easters stay in place for days, and “churn away,” she said, creating an overwash of water and mud, which stays along the shore and doesn’t immediately run back into the sea. By contrast, the hurricanes usually come through fast and bring a high storm surge, heavy downpours and high winds. They can cause flooding and destroy buildings, even by hurling debris into the backs of the houses.

Freedman began her talk with that famous 2007 picture of the hanging cottage, wedged over a cliff at Matunuck.

By the time the picture was taken following the Patriots Day storm, Freedman said, a series of storms undercut the bank where that house was sitting. Matunuck Beach consists of Aeolian silt, one of several types of sand and rock that erode easily. More than 50 percent of the R.I. coast is made of material susceptible to erosion.

Freedman showed aerial photographs to compare the coastline in 1951, 1985, 1997, 2008 and 2011. In 1951, she said, the aerial photograph shows the house behind “a nice, wide beach.”

In 1985, the beach also appeared wide, but the house next door was gone – washed away during a 1983 storm. By 1997, the aerial photograph shows unmistakable signs of a shrinking beach.

“In 1997, the beach continues to move landward,” Freedman said. “Several houses are now in the intertidal zone.”

That landward movement continued. The 2008 and 2011 aerial photographs show numerous houses at Matunuck Beach “close to the edge.”

In the 2007 photograph, part of the house foundation was exposed and so was the septic system. To avoid losing the house, the homeowner opted to move the cottage back across the street.

“But Matunuck isn’t alone,” she said. Aerial photographs of Green Hill taken between 1972 and 1981 show a similar change, as the wide beach in front of houses disappeared.

Geologist John Boothroyd, a Jamestown resident, has developed maps documenting the changes along the state shoreline, she said. The maps do show a few Rhode Island spots where the beaches are gaining, but overall, she said, “The south shore is an eroding shoreline.”

There are multiple reasons, starting with location. “Rhode Island is the first south-facing shoreline you hit when a storm is moving up the coast,” Freedman said. Also, residents should beware any storm that tracks to the west, as Hurricane Carol did in 1954.

“If the storm is tracking to the west, the Northeast quadrant is where you get storm surge,” she said. In 1954, when Hurricane Carol hit Rhode Island, the seas were running 7 feet higher than normal, and the storm also hit at high tide. With higher sea levels, the waves move deeper into the shoreline and crash against dunes or bluff, instead of landing on the beach.

The average erosion rate is 1.6 feet a year, she said, but that number jumps with a storm surge.

And recently, for reasons not related to any storms, the tides are higher and the sea levels have been rising.

“By 2050, we will be a foot over 1990 levels,” she said. “We’re at 3 inches over now. We could see 3 feet, maybe by the end of century.” Freedman said that 5 feet above today’s sea level is a possibility by 2100.

Climate change is behind rising sea levels and intensifying storms. The changes are already visible in some areas of Warwick and Wickford, where floods are occurring frequently. And beyond Rhode Island, similar forces have been at work.

The 2007 Patriot Day storm that wreaked coastal destruction in Rhode Island also took out homes in Saco, Maine, she said. In fact, there are examples of coastal erosion abound all over the world.

“Erosion happens all over place,” she said, defending her remark by showing slides of Surfside, Texas, the Bolivar Peninsula after Hurricane Ike, and the effects of a cyclone on Kingscliff, Australia.

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