Bulkheads have historically been used to reinforce coastlines, protecting shorelines from powerful wave action and erosion. However, these structures are thought to have negative long-term impacts on adjacent salt marshes but—up until now—no studies have quantitatively demonstrated the effects.
NOAA’s National Centers for Coastal Ocean Science and partners recently published a study—the first of its kind—unveiling a multidecadal assessment in which the team used remote sensing to investigate the long-term impacts of bulkhead structures positioned landward of salt marsh, a relatively common positioning of bulkheads along estuarine and coastal shorelines.
Using aerial imagery from 1981, 1992, 2006, and 2013 along North Carolina’s Bogue and Back Sounds, and Newport and North Rivers, the team identified 45 locations with bulkheads landward of the marsh. They compared each of those sites to 45 nearby locations without bulkheads over the same 32-year period.
The results of this study indicate that bulkheads may pose a significant threat to salt marsh survival. Net marsh loss was, on average, 180 percent greater where bulkheads were present. Salt marshes have a natural tendency to shift and migrate in response to fluctuations in sea level. Adding an armored structure, such as a bulkhead, can prevent the inland migration of salt marshes and increase erosion by wave energy back on the marsh shoreline, eventually causing the marsh to severely erode or disappear altogether.
The study suggests that proper land-use planning and conservation efforts, along with the use of living shorelines rather than hardened shorelines, where appropriate, might help protect these vital ecosystems and the many services they provide. View the full study in Coastal Research for additional details.
Partners in this study include Duke University, and North Carolina Division of Coastal Management.
This work is part of NOAA’s coastal resilience and restoration efforts and is supported by the Coastal Zone Management Act.