Estuarine Shoreline Stabilization
Bulkheads are the predominant shoreline stabilization method used in North Carolina
along estuarine shorelines. However, bulkheads have the potential to cause deleterious impacts
to coastal marshes that provide many useful ecosystem services. While there are currently alternatives to bulkheads that provide similar levels of erosion protection and minimize the impacts to coastal marshes, in North Carolina these alternatives are largely being ignored by estuarine property owners and marine contractors.
From 2008-2012, the Sustainable Estuarine Shoreline Stabilization project utilized a three part approach to address the critical coastal management issue os sustainable shoreline stabilization in North Carolina:
- Conduct field based research designed to quantify the impacts bulkheads have on the ecosystem services provided by the coastal marshes
- Construction of a demonstration project utilizing a living shoreline design (alternative to a bulkhead) to stabilize an eroding shoreline
- Dissemination of project results to the general public (coastal landowners, marine contractors, students and teachers) and natural resource managers
The project resulted in several key findings about shoreline stabilization impacts on marsh habitat and barriers to implementing alternatives to bulkheads:
- Bulkhead sites with no fringing marsh were at least 0.5 m lower in elevation than sites with marsh.
- Fringing marshes in front of bulkheads provided effective wave attenuation during storm events, whereas wave energy at unvegetated bulkheads is equal to or higher than incident wave energy.
- Denitrification (N removal via microbial activity) scales with marsh area, so that wider marshes provide greater N removal.
- Infauna distribution patterns were extremely variable by site, year, and region; but wider marshes had taxa more characteristic of well-established, interior marshes and narrow marshes and unvegetated sites were characterized by opportunistic species.
- Bulkheaded sites, with and without marsh, supported a lower abundance of birds compared to natural marshes. Bulkheads without marsh had much lower bird diversity and numbers.
- Marsh nekton abundance increases with increasing marsh width.
- Small narrow marshes in front of bulkheads provided a higher level of ecosystem services than expected, per unit area.
- Both waterfront property owners and marine contractors desired outreach materials be available online.
- Based on monitoring to date, shoreline stabilization using oyster reef with marsh plantings is a viable, cost-effective alternative to vertical bulkheads.
- Longer-term evaluation of elevation and vegetation is needed to determine the impact of bulkheads on fringing marsh sustainability.
For more information, read the final report: Sustainable Estuarine Shoreline Stabilization: Research, Education and Public Policy in North Carolina
Are you an estuarine property owner in North Carolina? The Weighing Your Options handbook provides information on protecting your property from shoreline erosion.