Town installs pilot dune‑stabilization systems at Madaket and Dionys; early sand gains reported

Leah Hill, the town’s Coastal Resilience Coordinator, told the Coastal Resilience Advisory Committee on April 8 that the department and Land Bank installed a two‑site pilot to test temporary dune‑stabilization technologies.

Hill said the pilot used products from Coastal Technologies — “cliff stabilizers” (temporary honeycomb‑style inserts anchored with stainless‑steel screws and planted with dune grass) and, where permitted, a second device the company calls a dune guard that captures windblown sand. “They are temporary devices that help stabilize the plants and help capture the sediment,” Hill said.

Why it matters: the pilot is an experiment to identify low‑cost, replicable tools property owners and the town can use to slow coastal bank erosion and encourage dune formation without permanent hard structures.

Sites and methods: crews installed four treatments at each site (Madaket and Dionys): cliff stabilizers with plantings; dune guards (to be permitted for fall/winter installation because of breeding‑season restrictions); beach grass plantings; and a control area with no treatment. Each treatment is about 400 square feet (roughly 1,600 square feet total at each site), and monitoring will include elevation surveys, plant density and mortality.

Hill said the Madaket site was chosen because a monitoring station there has recorded about 19 feet of coastal‑bank loss since 2022 and because adjacent residents had expressed concern about access. Dionys was selected to test the approach at a less rapidly eroding bank; Hill said that station has recorded about 5 feet of loss since 2022.

Cost, permitting and initial results: Hill said the installations were relatively inexpensive and that the combined pilot cost about $10,000. She reported a rapid initial response at Madaket: “I actually went out to Madaket yesterday, and after a week of them being installed, there has been a ton of sand accretion on top of the cliff stabilizers,” Hill said. The project received a Conservation Commission notice‑of‑intent permit and was routed to Mass Natural Heritage for comment.

Committee comment: members asked whether the plastic inserts remain visible after vegetation establishes, whether removing the anchors will disturb plant roots, and how reusable the materials are. Hill said the devices are designed to be removed after roots establish and that, because they are plastic and reusable, the town can redeploy them at other sites.

Next steps: the department will continue quarterly monitoring, evaluate differences between the two sites and publish results and installation guidance so private property owners can evaluate whether the approach suits their parcels.

Ending: Hill said staff will reassess performance this fall and report back; committee members requested a monitoring summary that includes cost per linear foot and links to procurement details so homeowners can replicate the approach if successful.