Managing Natural Assets to Increase Costal Resilience: Pointe-du-Chêne, NB

In 2020-21, the Municipal Natural Assets Initiative (MNAI) piloted the Coastal Resilience project Point-du-Chêne, N.B. to address the impacts of climate change on aging infrastructure, being realized by many coastal communities across Canada. The structures originally constructed to protect communities from storm surges are aging and unable to protect against bigger and more frequent storms caused by climate change. To address these challenges, the David Suzuki Foundation and the Municipal Natural Assets Initiative piloted the Coastal Toolbox (CT) model to determine what key advantages exist, if any, to implementing natural asset solutions in coastal areas of that community. The Coastal Resilience project’s two objectives were to: 1. Provide Pointe-du-Chêne and the Southeast Regional Service Commission (SERSC) with a quantitative assessment of the benefits that coastal natural assets can offer for flood and erosion protection from coastal storms. 2. Develop and pilot a modelling tool (the Coastal Toolbox, or CT) that coastal communities can further refine so they could understand and compare alternative natural asset management solutions to storm surge and coastal erosion. Outcomes of municipal natural asset management include cost-effective and reliable delivery of services, support for climate change adaptation and mitigation, and enhanced biodiversity.

Understanding and Assessing Impacts

As of the 2016 federal census, Pointe-du-Chêne was home to 716 residents. There are about 1,000 structures in the community based on building footprints provided by the Southeast Regional Service Commission (SERSC). Pointe-du-Chêne is also a destination for tourists and recreational users of nearby Parlee Beach, a provincially protected park. With recent hurricanes and storms, the community has experienced large-scale flooding and coastal erosion that have affected buildings and beaches (e.g., in 2000, 2010 and 2019). The local government recognized that it is as important to understand, measure, manage and account for natural assets as it is for engineered ones. The term municipal natural assets refers to the stock of natural resources or ecosystems that a municipality, regional district or other form of local government could rely on or manage for the sustainable provision of one or more local government services. Doing so can enable local governments to provide services such as stormwater management, water filtration and protection from flooding and erosion, as well as additional services such as those related to recreation, health and culture. Outcomes of what is becoming known as municipal natural asset management can include cost-effective and reliable delivery of services, support for climate change adaptation and mitigation, and enhanced biodiversity. Sea-level rise and tidal elevation estimates for Pointe-du-Chêne were obtained using the Canadian Extreme Water Level Adaptation Tool (EWLAT) and corroborated with Fisheries and Oceans Canada’s Tide Tables. Functional forms representing the relationship between flood depth and structure damages for different building types was used for estimating flood damage. This data was used as an input for the Coastal Toolbox (CT) model and make a business case for natural assets and the benefits they provide in a changing climate. For more information on the different types of data, see the Technical Guidance Document in the resource section.

Identifying Actions

Local governments have numerous ways to manage natural assets. The Municipal Natural Assets Initiative (MNAI) uses methodologies and tools rooted in standard asset management and provides a range of advisory services to help local governments implement them. MNAI has developed the methods and tools with significant investments, piloting, refinement, peer review and documentation of lessons in multiple Canadian provinces. Many MNAI tools to-date have focused on surface water quality and quantity. The development of a tool called the Coastal Toolbox (CT) is a first attempt to extend the natural assets methodology to coastal issues. Funding and project support through the David Suzuki Foundation, overall project coordination by MNAI, and support from a technical team all contributed to the CT development. The project team then took the following five steps: 1. Identified and selected coastal protection options for modelling. 2. Incorporated coastal protection options in the Coastal Toolbox. 3. Specified sea level rise assumptions and constructed design storms. 4. Developed simulation modelling using the Coastal Toolbox. 5. Evaluated results and estimated benefits.

Implementation

Natural asset management strategies require a multi-disciplinary, team-based approach. The MNAI process therefore begins with an initial engagement session with community representatives from across a range of disciplines. In April, June and September 2020, the project team held three multi-stakeholder workshops to discuss, identify and prioritize existing coastal natural assets, and to isolate the most promising candidate management options that would reduce damages from storms and provide other co-benefits. These workshops included local residents as well as participants and experts from the SERSC (planning, geomatics, GIS), the Shediac Bay Watershed Association, Greater Shediac Sewerage Commission, Southeast Planning Review and Adjustment Committee, Government of New Brunswick, New Brunswick Provincial Parks, New Brunswick Geological Survey, New Brunswick Tourism, Heritage and Culture, New Brunswick Climate Change Secretariat, New Brunswick Environment and Local Government, Natural Resources Canada (NRCAN), Environment Canada, Department of Fisheries and Oceans Canada (DFO), Parlee Beach Provincial Park and the Nature Conservancy of Canada. With input from a stakeholder group, the project team developed a list of 11 natural asset management options and assessed them against a set of criteria. Based on those considerations, the team identified five options for modelling: • Dune improvements • Beach nourishment • Shoreline planting • Eelgrass planting • Submerged structures The project team evaluated the performance of the five selected natural asset options under an assumed sea-level rise (using emissions scenario RCP 8.5). Coastal flooding and erosion at Pointe-du- Chêne are primarily driven by a combination of “still water levels” and wave impacts (wave run-up), where the former term is used to describe average water surface elevation including contributions from tides, storm surges and sea-level rise. Using the Coastal Toolbox, each design storm was simulated over 100 years with and without each of the five natural asset options across all natural asset parameter combinations. For each natural asset option, the cost of beach loss and flood damages were calculated over a 100-year time horizon.

Outcomes and Monitoring Progress

Flood estimates from the CT indicate that, compared to erosion, flooding is a much costlier hazard for Pointe-du-Chêne. For the individual natural asset options assessed, those applied to the Parlee Beach NW segment consistently generate the greatest long-term avoided flooding benefits in absolute costs. Given the impacts from flooding, even small improvements can have significant cost savings. Flooding is the greatest storm-related threat to the community, with total projected flood damages over a 100-year period exceeding $182 million (2020 CDN). While natural asset enhancements would only provide a one to four per cent improvement in flood mitigation, the associated cost savings are in the $1.4 to $7.6 million range. This means natural asset solutions for flood management should be recognized, particularly considering the co-benefits they can offer, like habitat provision, aesthetic appeal and erosion protection. Erosion results from applying the Coastal Toolbox in Pointe-du-Chêne indicate shoreline planting generates the greatest long-term benefits from avoided erosion costs ($10.89M), followed by beach nourishment ($9.55M) and dune improvement ($8.22M). The project team determined that total potential losses from erosion are approximately $19 million over a 100-year time horizon. Solutions like shoreline planting, dune improvement and beach nourishment applied along all segments of Parlee Beach could reduce damages by 40 to 60 per cent, for a cumulative benefit of $8 to $11 million. Overall, this pilot study demonstrated that: 1. The CT is a rapid and easy-to-use tool that is sufficient for high-level initial screening and for quantifying the benefits associated with coastal natural assets. 2. There are challenges associated with applying a generic tool to different types of coastlines; at its current stage of development, the CT will be most applicable to areas with sandy shores. 3. Current applications of the CT will likely still require local knowledge and external professional expertise for some key modelling steps. 4. The CT tool offers a valuable learning and assessment framework.

Next Steps

Local governments wishing to consider using the CT should review the full technical guidance document as well as the results from the Town of Gibsons pilot. Current applications of the CT will likely still require combining local knowledge with professional expertise for some key modelling steps. The resulting screening will help determine whether to proceed with more detailed investigation and research related to natural asset approaches. Several assumptions are associated with the baseline parameter estimates, and a useful next step would be to examine the impact of these assumptions on results by performing various sensitivity analyses. For example, the erosion model’s cost estimates rely on a median assessed value for land located near the coast ($50/m2). In reality, land values can vary considerably, so adjusting this amount by ±20 per cent would provide an uncertainty range for consideration. Lastly, given the comparatively large costs associated with flood damages in Pointe-du-Chêne, prioritizing sensitivity analysis for this hazard is recommended.

Resources