For decades, researchers have taken measurements at nine sites along Rhode Island's southern coastline, from Misquamicut Beach to South Kingstown Town Beach. Today, eight of these beaches are surveyed regularly, all except the Cha-EZ site.
The data collected show that beaches do not stay the same: they change measurably over the decades. According to the researchers, all the surveyed beaches have undergone significant changes in recent decades. The Moonstone and Green Hill sites are eroding fastest, while others show more moderate or minimal net erosion. There is one exception, however: the East Beach 1 site has shown some net accretion, meaning beach expansion, since 1963.
The changes are not only long-term. As regular visitors know, a beach's shape also changes seasonally through erosion and sediment deposition. Winter storms typically move sediment offshore, while gentle summer waves help return sand to the beach. This cycle is governed by ocean physics and the climate patterns affecting the state, also known as the “Ocean State.”
Powerful hurricanes or other storms bring strong waves and currents that can dramatically change a beach's shape, even eroding the adjacent dune and infrastructure. A clear example is 2012, the year of Hurricane Sandy: the data show major erosion at many Rhode Island beaches during that period.
Because of chronic erosion, the beach has moved inland over time at several study sites. This means the beach measured today is in a different position from where it was in the past. On the charts, a shift in the profile's position to the left indicates that the beach profile has moved landward. An elevation profile may therefore look the same today as it did in the past, while its position has actually shifted because of erosion.
To calculate how much sediment has eroded from a shoreline, aerial observation alone is not enough; we need to know how elevations, or topography, have changed. Beach volume is therefore calculated by adding up the area under the beach profile. This allows researchers to track changes in sediment volume at each survey site.
A beach's slope also changes over time. According to the researchers, the slope is related to the sediment making up the beach, as well as waves, tides and recent storm activity. Some surveys, however, did not extend far enough down the beach, potentially making slope measurements inaccurate in some cases.
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