Promoting Green Roofs in the Tantramar Region to Improve Freshwater Management and Increase Climate Resilience

In 2020, with funding from Environment and Climate Change Canada’s Eco Action Community Funding Program and the Mount Allison Students’ Union Green Investment and Small Change Fund, EOS Eco-Energy coordinated the installation of two extensive-type green roofs on buildings in the Tantramar-Memramcook area of southeast New Brunswick. The green roofs will help manage stormwater naturally and reduce freshwater flooding. The green roofs project also forms part of a larger initiative by EOS that supports water quality monitoring and community resilience to climate change.

The goals of the project are to reduce runoff from buildings and manage stormwater with green infrastructure; promote the benefits of green roofs; increase community resilience to climate change; and educate the public, including youth and small businesses, about community resiliency including green roofs.

Green roofs (also called vegetated roofs or living roofs) are planted gardens on the tops of buildings, covering all or part of the roof. Green roofs have many benefits. Most importantly they absorb rainwater and help to reduce local flood risk. They also provide additional insulation for the building and can extend the life of the roof. Green roofs increase biodiversity, create natural habitats for birds, insects and other wildlife, and can help lower urban air temperatures by mitigating the urban heat island effect, filtering pollutants and sequestering carbon. They also create attractive spaces that can help reduce stress, increase connection with nature, and provide space to grow food.

Understanding and Assessing Impacts

Downtown Sackville and much of the larger Tantramar Region have been historically affected by over-land freshwater flooding. Flood mapping recently released by the Government of New Brunswick expects flooding to become more frequent and severe towards the end of the century.

The Town of Sackville in 2016 released a Corporate Climate Change Adaptation Plan to better understand how climate change was projected to affect the community. The plan presents an adaptation vision for the Town of Sackville, and details climate change impacts affecting the municipality including changing precipitation patterns, sea level rise, intensifying storms and storm surges, and rising temperatures. A series of flood scenarios are also included. The plan summarizes previous public engagement sessions, including risk and vulnerability assessments.

Sackville has experienced major flooding when 100mm of precipitation falls over a 24-hour period. Climate modelling suggests that precipitation events will become less frequent, but the intensity of the storms is expected to increase.

Impenetrable surfaces and impervious materials used in construction such as concrete and asphalt inhibit the absorption and increase stormwater runoff and put pressure on storm drains. Stormwater runoff can cause erosion, contribute to water pollution, localized flooding, and even decrease groundwater levels. Stormwater runoff from some of these areas can also negatively impact water quality due to pollutants and sediment accumulation.

Identifying Actions

A community-based climate change resilience guide was created for Sackville, NB. The guide was created by and for residents, businesses and organizations in Sackville and is meant to complement the municipal climate adaptation plan. The guide is a collection of actions related to health and wellness, education, food security, green spaces, water, flood risk, emergency planning, sustainable energy, transportation, local economy, collaboration, communication, and citizen engagement. Green roofs are one of the many actions identified to increase community resilience in Sackville.

EOS staff conducted extensive research on green roofs, attended workshops organized by the New Brunswick Environmental Trust Fund, and consulted with experts, including botanists, engineers, and green roofing companies in preparation for the project. EOS worked with the Town of Sackville and Mount Allison University to identify both sites for the green roofs. Engineering and architectural firms, as well as a local roofing company, were consulted to perform site analysis and design.

In year one of the project, engineering assessments were completed for the Sackville Town Hall roof and the McCain Student Centre roof at Mount Allison University. Both buildings were deemed suitable for green roofs, and a building permit was not required for the Town hall site, due to the existing green roof. Engineering assessments determined a suitable soil depth for the Town Hall site of 8 inches, and 6 inches for the Mount Allison site.

During spring 2021 EOS staff worked with the Town of Sackville, Mount Allison University staff and students, green roof experts and local botanists to develop a suitable plant list for the green roofs. There were some differing opinions among the experts regarding local climate and native species. Plants were selected that are not too tall (due to the shallow soil depth on both roofs), able to withstand both dry and wet conditions and were native to the region. Edible herbs and sedums were also selected to help fill the roof area. The Town Hall roof has a large shady section, so shade-tolerant plants were included. The plants were sourced from various nurseries and greenhouses in southeast New Brunswick.

Implementation

The Sackville Town Hall building was designed for an inverted green roof when it was initially built. Initial designs were expanded, resulting in a total area of 1856 ft2. It already had drains and appropriate design features and had a portion already covered in a green roof. Construction of the new green roof, began in July 2021, with a local landscaping company installing the waterproof membrane, root barrier, drainage layer, filter layer, moisture retention layer, and growing medium (soil type). Planting began in August with the help of local volunteers and included various grasses, native flowers (echinacea, black-eyed susans, yarrow, asters, etc.), native berries (strawberries and blueberries, which were transplanted from the wild), and herbs (chives, mint, oregano, thyme, and more). Educational signage, benches, and solar lighting were also installed so the site can be utilized for evening events.

The Mount Allison site required initial remedial work, including a drainage system installation and a leak detection system. Various designs were considered, resulting in a 1008 ft2 Including 758 ft2 planting area, and 250 ft2 of pathways to access the garden. Due to several complications and delays (including contractor shortages and covid-19), the University was approached to assist in the funding and implementation of the site.

Outcomes and Monitoring Progress

Over 500 native plants were planted and a total of 3,814 ft2 of green roof area was created as a result of this project, with the planting of the Mount Allison University site scheduled for Spring 2022. Monitoring included plant survival and maintenance needs, as well as rainwater retention. During Hurricane Ida, over 80 mm of rain fell causing flooding in portions of downtown Sackville. No standing water was recorded on the roof of the Town Hall site, and it is expected that at a depth of 7 inches, the fully saturated green roof can retain 7.89L/ft2 of precipitation.

EOS promoted green roofs in a variety of ways including educational trilingual rooftop signage, brochures, a webpage, youth lesson plans and rooftop activities, virtual tours, videos and social media posts and many news media stories online, on the radio and evening television news.

Professors at the university plan to use the green roof for an outdoor living green lab and invite students from kindergarten to post-secondary levels to participate in learning opportunities.

In addition to the two green roof sites, a host of materials were created to support access and education on the project. Educational signs were designed to introduce green roofs, the construction process, and their many co-benefits. These signs are also displayed in French and Mi’kmaq. EOS staff also created a bilingual webpage and brochure to detail the project.

A Green Roof Activity Guide, Green Roof Tours, and virtual tours and videos were also provided by EOS staff for students and members of the public.

Unfortunately, due to complications surrounding Covid-19, several in-person events had to be cancelled and engagement targets were not met; however, these events were replaced with virtual online content which continues to generate engagement.

Next Steps

EOS encourages the public to visit the green roofs to learn more about them. In the future, EOS and its partners will offer public events and classes on the roofs. The creation of more green outdoor public meeting spaces during a global pandemic is also incredibly timely and useful, and EOS looks forward to the benefits of green roofs in the community for many years to come.

Resources

Link to Full Case Study

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