Ballston Beach Barrier Dune Restoration, Truro, Massachusetts
Barrier dunes are tricky to read and nearly impossible to restore, unless you find a strategy that uses the natural energy already flowing through the system. A unique Community Partnership was created, to meet this challenging restoration effort. The photo directly below was taken at the end of one year of restoration efforts, using an innovative, biomimicry sand collection system. The system raised the broken dune elevation by 14 feet, ending our concerns about over wash.
Ocean storm overwash in Ballston Beach barrier dune system, destroys freshwater marsh at head of Pamet River in Truro, Massachusetts.
Barrier beaches and barrier dunes are among the most fragile and most highly protected resource systems in Massachusetts. These systems are fragile because they change location in response to storm events, which discourages establishment of stabilizing vegetation. These systems are valuable because they offer protection to important inland resource areas. The Barrier dune system at Ballston Beach protects the freshwater marsh at the head of Truro’s Pamet River.
Overwash fan marks remains of barrier dune, after ocean entered marsh through pedestrian paths. After multiple, similar events, fresh water marsh has become degraded habitat with invasive phragmites reeds.
For thousands of appreciative visitors crossing these dunes each year, Ballston Beach is a second home. Being visitors, there was no way for them to understand, that barrier dunes are only held together by vegetation, which keeps sand in place and collects new sand during storms. That same vegetation that withstands 80 mph storm winds, cannot survive being directly walked on. Without the vegetation layer, storm winds quickly strip off sand, lowering the walkway elevations by as much as six or eight feet.
Storm overwash events are a fact of life for barrier dunes and a part of the overall coastal process on the Outer Cape. However, Ballston Beach’s barrier dune system has had uncomfortably frequent overwash events. Each event begins with storm waves gaining access to the freshwater marsh through the lowered elevations of the pedestrian pathways. Storm waves, surging through the center profile of the dunes, transport sand and saltwater deep into the freshwater marsh. At this point, North Truro and Provincetown are islands and connecting public roads face the possibility of flooding.
Our winter intern Audra, at Ballston Beach. Audra is a UMass graduate in Environmental Science and is taking post grad courses in Coastal Zone Management and Coastal Ecology.
Safe Harbor has developed an innovative restoration model, which uses storm winds to restore eroded coastal habitat. This low-tech system uses specific patterns of 24” sand fencing, to duplicate the wind resisting performance of beach grass. This passive strategy stabilizes eroded areas while collecting new sand, often raising elevations up to two feet a year. The fencing system can be quickly installed, using a rubber mallet to tap each slat into the sand. No excavation or posts are required. New layers of fencing can be placed to create a form compatible with adjacent dune profiles.
Zig zag pedestrian paths avoid shotgun blow outs. 24″ sand fence collects sand from storm winds.
The restoration system we believe in, works with and not against, the natural energy of coastal habitats.
Camille at Ballston Beach, setting in the ocean side lines of fencing.
Perhaps the most unique features of this innovative sand capture system are the front rows of “surfline” fencing. This is only the second time we have used this strategy, which is based on our research with fencing failures, which determined the need for wave wash to move into and then back out of this wash zone. These low impact surfline fences have every other slat removed, are shorter than the 24″ sand capture fencing and are cut every 5 feet of fence length, to prevent full wash away. We believe this new strategy has the ability to slow down wave wash just enough to capture sand from it.
Unique and innovative, this surfline fencing is designed to capture sand from wave overwash.
Standard responses to coastal erosion use structural components and cost hundreds of thousands of dollars. When the coastline itself moves, we can’t put it back.
Fencing with closely spaced slats, does not allow wave wash because it creates structure, not a soft solution. Fencing that fails to allow passage of wave wash may ultimately fail.
