Forecasting Economic Damages from Storm Surge Flooding in the Tantramar Region of New Brunswick

To evaluate the potential for community adaptation to offset the expected costs, authors drew on the input from local stakeholders in combination with general flood mitigation literature to define four adaptation strategies. To demonstrate how communities, such as the Town of Sackville and Tantramar region, assess the influence of adaptation strategies a series of adaptive strategies or options were identified. Previous research explored some adaptations through a stakeholder engagement process. Feedback from the stakeholder focus group held on April 19, 2011 identified several adaptation options, for example: Move sewage treatment plant, increase the height of dykes, and relocate residents and businesses. These suggestions formed the starting point for scoping the adaptation strategies. Drawing on input from local stakeholders in combination with general flood mitigation literature, the research team outlined three adaptation scenarios for analysis in addition to the ‘status quo’ or baseline scenario as a starting point for the Tantramar region to consider: Status Quo, Dyke Top-up, Relocation, and Natural Infrastructure. To capture local knowledge, expertise, and policy implications, a half-day workshop was held on May 31, 2012 to present preliminary findings and discuss the feasibility, both physically and politically of each adaptation scenario. The workshop brought together a select group of local experts and stakeholders representing a range of knowledge areas including: local policy, hydrology, agriculture, dyke management, and wetland management. Each scenario was explored in detail, discussing their effectiveness to reduce flood risk, policy implications, and expected costs. The general consensus was centred on the timing of scenarios. For instance, dyke top-up was considered the most effective short-term solution, allowing time to develop longer-term strategies and policies necessary to provide more permanent protection from flood vulnerability.

As a result discussions with stakeholders, the following adaptation scenarios were redefined to the following:

1. Status quo (baseline), assuming that no mitigation or adaptation measures are undertaken and all system changes can be attributed to climate change.
2. Dyke top-up, involving a 1 m increase in dyke height from 8.5 m to 9.5 m above sea level, a 2-3year delay to coordinate policy and secure funding, and a 5 year work plan resulting in completion by 2020.
3. Relocation, where highly vulnerable properties are relocated to areas of limited vulnerability. This scenario does not imply a forced relocation or expropriation. Rather, it captures the potential avoided damages that would result if relocation occurred. Such relocation could be supported through a range of policy options including tax incentives and strategic land-use planning.
4. Mixed strategy, involving both dyke top-up and relocation.

For the purpose of this analysis it was assumed that it would take 13 years to coordinate policy and funding to support this strategy; and relocation would commence in 2025, and would not be complete until 2045.  There are many possible adaptation strategies that could be explored. The strategies chosen for this project are meant to showcase the two likely to provide significant benefits in terms of damage costs avoided. Also, due to data limitation implantation costs could not be calculated in much detail.

A common approach to assess the direct impacts involves the use of something referred to as a “stage damage curve”, which relates the depth of floodwater to the expected severity of the damage. Fortunately, the relationship between flood depth and damage to a given asset is relatively consistent, justifying the use of already established stage damage curves produced by the U.S. Army Corps of Engineers. Time and resource constraints did not allow the measurement of intangible assets. Without detailed historical data on these flood related damages it is difficult to incorporate them into the comparative assessment conducted in this report. While some historical data was available (summarized in Section 2.2) it was not detailed enough to generate relationships between flood damages and flood return periods nor did it fully capture the missing components described above. Finally, the analysis assumes no changes to population, increases in urban development, or other changes to social, economic, and spatial configuration of flood vulnerable areas. In other words the analysis holds 2012 conditions constant. While this is an unrealistic assumption, it allows for unbiased inter-temporal comparison.

As a result of the work accomplished, it is recommended that future research explores the public attitudes and preferences for adaptation and minimization of flood risk and vulnerability. It also recommends that future research should explore multi-attribute evaluations of flood management as the Tantramar region continues to improve its understanding of the pressures it faces imposed by a changing climate. As well, it will be important to gain an understanding of the human health and well-being benefits of flood alleviation. Ultimately, however, the Tantramar region needs to develop an integrated strategy that brings together key stakeholders to properly manage flood risks being faced by all stakeholders to ensure both short and long term reductions in flood vulnerability.

Link to Full Case Study

Additional resources:

• Tantramar Dykelands Infrastructure at Risk Sackville, New Brunswick

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