Green Shores and Hurricanes
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. On the east coast of Canada for example, shorelines provide important sources of food, medicine, and cultural values as gathering places of Atlantic Indigenous peoples. Other parts of the population rely on shorelines as well, and 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 the location for 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 that 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 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.
Resilient shoreline: Island Highway West Vancouver Island, Green Shores Site 5 Years Post-Restoration (Credit: SCBC)
Allowing the natural movement of sediment and water along the shore means there is more sediment 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 along with planting native shoreline species - which have root systems that help to keep soils in place - aid in retention of 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 in close proximity to 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 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 do, and they may have different root structures, toxicity levels, or alter the habitat that important native species rely on 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 the species that poses 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.
Glossy Buckthorn - New Brunswick Alliance of Lake Associations, 2022
Mahone Bay Living Shoreline
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 away. 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. The addition of vegetation to a system also contributes to storing carbon from the atmosphere and producing 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.
Coastal Action’s living shoreline project in Mahone Bay, Nova Scotia, was recently implemented to protect their iconic coastal infrastructure. Researchers were concerned that Hurricane Fiona would destroy the new plants that had been used for shoreline restoration only two months prior to 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. Below are photographs before and after the hurricane, taken from the same vantage point a week apart, which demonstrate 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, aka “the evil spirit of the wind” (Mayans & Tikal, n.d.), Green Shores certified shorelines provide the space for natural processes to occur, while protecting shoreline properties and homeowners from storm impact, flooding, and erosion.
Resources
If you want to learn about how to get started with a Green Shores project on your shoreline, click the Green Shores button!
For more resources on nature-based solutions to climate change, click the Nature-Based button!
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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 https://nsinvasives.ca/glossy-buckthorn/
Province of Nova Scotia. (2019). Public and Stakeholder Consultations on Coastal Protection Legislation in Nova Scotia. Retrieved on November 30, 2022 from https://novascotia.ca/coast/CoastalProtectionLegislationConsultationReport.pdf
University of Rhode Island. (2020). Terrestrial Impacts. Hurricanes: Science and Society. Retrieved November 8, 2022, from http://www.hurricanescience.org/society/impacts/environmentalimpacts/terrestrialimpacts/