Nature-Based Solutions for Coastal Resilience: The Mahone Bay Living Shoreline
By Kailey Nichols, NSEN Journalism Volunteer
Coastal ecosystems are highly vulnerable to the impacts imposed by climate change. Generally, this is attributed to the accelerated shoreline erosion, increased prevalence of storms and storm surges, and greater frequency and intensity of flooding events. As a coastal province, Nova Scotia is sensitive to these factors especially when considering the large population of people that live near the coast.
To address complex issues, like the vulnerability of our coasts, we need innovative ideas. Historically, we have used hard infrastructure such as dykes and rock armour. Dykes are earthen barriers that were created to convert salt marsh systems into agricultural land (Bleakney, 2004), while rock armour is a barrier made with large boulders to prevent erosion of shorelines. Many of these structures are failing or posing other problems such as intensified erosion surrounding the structure or impacting neighbouring coastal habitat. As a result, we are noticing a shift in the way we are addressing these problems, leaning from building in nature, to building with nature.
What are nature-based solutions?
Nature-based solutions (NbS) are defined by the International Union for Conservation of Nature (IUCN) as “actions to protect, sustainably manage, and restore natural or modified ecosystems, that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits” (Cohen-Shacham et al., 2016). When applied to coastal ecosystems, there is potential to address complex problems such as climate change by increasing our resiliency overall without sacrificing the integrity of critical ecosystems.
What is a living shoreline?
One form of NbS that has gained popularity in recent decades has been the living shoreline approach. The living shoreline approach involves the use of natural materials and features to offer shoreline protection and to reduce erosion. These approaches can take many different forms but those involving tidal wetlands to stabilize the shoreline are quite popular. When employing these approaches, natural materials such as woody debris, native vegetation, haybales, and mulch, should be the dominant component of the living shoreline. However, in higher wave energy settings, more rigid shoreline elements such as rock sills may be used for increased stability, offering a hybrid approach.
Case Study: The Mahone Bay Living Shoreline
The Mahone Bay Living shoreline demonstrates an example of hybrid living shoreline approach. For this project, Coastal Action partnered with the Town of Mahone Bay, CBCL, Transcoastal Adaptations, Saint Mary’s University, and CB Wetlands & Environmental Specialists to carry out the largest known living shoreline in Nova Scotia to date. The living shoreline was installed along a 60-metre stretch of Edgewater Steet in front of the town’s famous three churches to protect the infrastructure from rising sea levels and storm surges.
The living shoreline was characterized by three main components:
1. Rock sill: hard infrastructure that runs parallel to the shoreline to enhance stability of the softer components.
2. Tidal wetland: shallow sloping area comprised of native, salt tolerant species (halophytes) that can withstand frequent flooding. These plants reduce wave energy and shoreline erosion by stabilizing the sandy substrate.
3. Vegetated bank: Graded area planted with native shrubs and herbaceous perennials tolerant to salt spray but less tolerant to inundation to protect the bank.
Construction of the living shoreline began in June 2022 which involved heavy equipment bringing in the fill for the substrate, grading the marsh component and the vegetated bank, and installation of the rock sill. Shoreline planting was carried out in the end of July 2022 over two days, which involved volunteers from private industry, NGOs, and community members coming together to plant out 1250 plants within the tidal wetland component and vegetated bank, supplied by an up-and-coming salt tolerant plant nursery – Rising Tide Nursery.
Volunteers planting the tidal marsh component of the living shoreline. (Photo: Kailey Nichols)
Volunteers planting the vegetated bank. (Photo: Kailey Nichols)
This project demonstrated a perfect example of how interdisciplinary approaches allow different perspectives and knowledge to work collaboratively to facilitate restoration success. Community engagement played an important role in promoting educational awareness and communal stewardship, providing a role model for future living shoreline projects in the province.
From this project, it is the hope that we can learn how effective living shorelines can be. With hard infrastructure such as rock armour, the structure will weaken over time. With soft infrastructure such as the living shoreline approach, the structure is the weakest it will ever be when first planted. Over time, it will strengthen due to the establishing root system and dispersal of plant species to establish a dense vegetative cover. Plus, living shorelines are great habitat for fish and birds, and ducks have made themselves at home right away in Mahone Bay!
Ducks enjoying the living shoreline on the same day it had been planted. (Photo: Kailey Nichols)
For more information on this project, check out the links below!
https://www.mahonebaylivingshoreline.com/
https://www.mahonebaylivingshoreline.com/updates
References
Bleakney, S. J. (2004). The Art and Science of Dyke Construction. In Sods, Soil, and Spades” The Aciands at Grande Pré and Their Dykeland Legacy (Ch. 5, pp 44-70). Montréal, QC: McGill-Queen’s University Press.
Cohen-Shacham, E., Walters, G., Janzen, C., & Maginnis, S. (2016). Nature-based solutions to address societal challenges. Gland, Switzerland: International Union for Conservation of Nature.