Sand in Salisbury is usually lost during storms and during the winter months, Hughes said. A good portion stays close to shore, gathering in a sandbar that gives the sand back a little at a time in deposits left by waves as they wash to shore during the spring and summer. But some sand is lost forever, he said, making its way south to places unknown and to places nearby, such as the Merrimack River, which is dredged periodically to open it up to navigation.
"I think it's time for CZM to gather more data on the beach for years after 1994," Hughes said. "We can't use short-term data to predict long-term erosion rates. You need long periods of time to estimate the long-term erosion rate."
CZM coastal geologist and hazard coordinator Rebecca Haney said erosion and accretion along Salisbury's shoreline — as in other coastline areas — varies a good deal. Much depends on the energy of the waves and their direction and the condition of the offshore sandbar that — when healthy — can dissipate the energy of the waves before they hit the beach.
"In order for a beach to sustain itself and not erode, there needs to be a certain volume of sediment (sand) feeding the system," Haney said. "The primary source of sand for Salisbury and Plum Island is an offshore delta formed when the glaciers melted. That delta has been depleted, and not as much sediment in coming back onto the beach."
Haney said CZM hopes to do a regional sediment study to track sediment movement and produce a long-term sediment management plan. An update of the shoreline changes since 1994 is something CZM would like to do through aerial photography, she said. That and the sediment study need funding in the state budget before they can happen.