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

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.

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.

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.

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.

Link to Full Case Study

Additional Resources:

• Defining and Scoping Municipal Natural Assets (September 2017)
• Managing Natural Assets to Increase Coastal Resilience: Guidance Document for Municipalities July 2021