How Would a Green Shores® Certified Project Stand Up in a Hurricane?
Hurricanes are natural forces that exacerbate natural processes like coastal erosion and flooding of shorelines. These same areas are exceptionally attractive spaces for human use and settlement. In the province of Nova Scotia, around 70% of residents live in coastal communities (Province of Nova Scotia, 2019). These coastal or lakeshore areas provide efficient transportation routes, aesthetically pleasing views, widespread cultural heritage and identity, and ample recreation opportunities. However, the desire to live along shorelines brings development, including human infrastructure, which cannot often easily adapt to the dynamic nature of shorelines.
Green Shores projects aim to build resiliency for shorelines by restoring natural processes that can be disturbed by human infrastructure and activity. Hard armour infrastructure, such as bulkheads, reflect wave energy causing the sediment at the base of the structure to be swept away through a process called scouring. This makes the hard armour structure highly vulnerable to collapse or failure. Soft infrastructure is designed to absorb wave energy. For example, planting native vegetation helps dissipate wave energy through friction, allowing for reduced erosion and deposition of sediments on the shore (ANCRIM, 2017). The Green Shores Credits and Ratings systems reward the maintenance of natural shorelines or restoration through the removal of hard armouring. By creating a more natural, vegetated shoreline interspersed with organic materials, Green Shores projects also improve habitat quality for important species, such as herons or turtles, while also improving their resilience to hurricanes.
Allowing the natural movement of sediment and water along the shore means more sediment is available in the system for deposition. Structures perpendicular to the shore, such as groynes, trap sediments, leaving little to replenish any erosion further along the shore (ANCRIM, 2017). Removal of structures such as groynes and planting native shoreline species with root systems that help keep soils in place aid in retaining sediments on the shore, which in turn provides nutrients for plant growth (University of Rhode Island, 2020). Permeable shoreline surfaces can help to absorb any excess rainwater or runoff from hurricanes and can help to filter pollutants out of the system.
Living near large bodies of water, especially along the ocean coast, is desirable for many reasons but poses a threat to the safety and integrity of houses and buildings. Shoreline areas with long fetch (the distance over which winds can move over water without being intercepted by bodies of land, vegetation or structures) have more time and space for waves to gain speed until they hit the shore (Encyclopedia Britannica, 1998). Green Shores projects promote set back or retreat of important infrastructure on the property to avoid as much of the destructive wind, rain, and wave forces a hurricane brings. A vegetative buffer can be added to the shoreline to take the brunt of the force away from the infrastructure on the property.
Just as other plant species can use hurricane winds to disperse seeds and spread widely, so can invasive species use these same winds, floods, and habitat disruption to colonize broadly. Invasive species outcompete native species for resources. Invasive plants don’t necessarily provide the same ecosystem services as native plants; they may also have different root structures and toxicity levels or alter habitats relied upon by important native species to survive. For example, in Nova Scotia, Glossy Buckthorn (a species native to Europe and Northwest Asia) is an invasive species that completely takes over coastal systems, wetlands, and forests and is considered to pose the biggest threat to native flora communities (Nova Scotia Invasive Species Council, 2021). Invasive species removal is included in the Green Shores Credits and Ratings Guide and can help slow the spread of invasives across habitats.
Living shorelines are an example of the application of Green Shores principles and are becoming a popular adaptation strategy for climate change and storms, and for good reason. Shorelines with vegetated buffers have more structure within the ground to keep sediments from eroding. As previously mentioned, species close to the water can slow wave energy through friction; plus, their roots draw some of the excess water from the ground in flood or rainfall events. Adding vegetation to a system also stores carbon from the atmosphere and produces oxygen. By adding more vegetation to the shoreline, wildlife can use that habitat as protection from hurricanes, increasing their resistance to storms, adding aesthetically pleasing sights and sounds to a shoreline, and contributing more life to a living shoreline.
“Despite Fiona decimating much of the rest of Atlantic Canada, the Mahone Bay living shoreline survived the storm with little to no damage.”
Coastal Action’s living shoreline project in Mahone Bay, Nova Scotia, was recently implemented to protect its iconic coastal infrastructure. Researchers were concerned that Hurricane Fiona would destroy the new plants used for shoreline restoration only two months before the hurricane. Despite Fiona decimating much of the rest of Atlantic Canada, the Mahone Bay living shoreline survived the storm with little to no damage. While the strongest part of this storm system did not pass through this area, the native plant roots still managed to protect the installed coastal sill from the intense wind, waves, and storm surge that occurred across the Atlantic provinces. The below photographs were taken before and after the hurricane from the same vantage point a week apart, demonstrating the integrity of living shorelines sitting in the path of intense storms.
-
- Mahone Bay living shoreline at low tide, September 22, 2022, pre-Fiona
-
- Mahone Bay living shoreline at low tide, September 29, 2022, post-Fiona
While nothing can stop hurricanes, Green Shores-certified shorelines provide the space for natural processes to occur while protecting shoreline properties and homeowners from storm impact, flooding, and erosion. If you want to learn how to get started with a Green Shores® project on your shoreline, click here! For more resources on nature-based solutions to climate change, click here!
References:
Atlantic Network for Coastal Risks Management (ANCRIM). (2017). Overview of soft coastal protection solutions. Retrieved November 29, 2022 from 2_Outil2_56P_EN.pdf (corimat.net)
Encyclopaedia Britannica. (1998). Fetch. Retrieved November 29, 2022, from fetch | oceanography | Britannica
Mayans and Tikal. (n.d.). Huracan. Retrieved November 8, 2022, from Huracan – History of Ancient Mayan God Huracan a ‘Major God of Creation’ (mayansandtikal.com)
Nova Scotia Invasive Species Council. (2021). Glossy Buckthorn Fact Sheet. Retrieved on November 9, 2022, from Glossy Buckthorn – NS Invasive Species Council
Province of Nova Scotia. (2019). Public and Stakeholder Consultations on Coastal Protection Legislation in Nova Scotia. Retrieved on November 30, 2022 from CoastalProtectionLegislationConsultationReport.pdf (novascotia.ca)
University of Rhode Island. (2020). Terrestrial Impacts. Hurricanes: Science and Society. Retrieved November 8, 2022, from Hurricanes: Science and Society: Terrestrial Impacts (hurricanescience.org)
