Can We Mitigate the Costs of Flood Damage Through Wetlands?

Introduction

It is unequivocal that human beings have changed the climate (Intergovernmental Panel on Climate Change [IPCC], 2021). These changes have caused an increase in the frequency and intensity of weather extremes, including heavy precipitation events (IPCC, 2022). Heavy precipitation events and floods cause damage to homes, infrastructure, and the livelihood of individuals within impacted communities (IPCC, 2022). Reducing the effects of floods is crucial to adapting to the changing climate and reducing current and future suffering.

Wetlands are environmental sponges and can be used to prevent flooding. They have the ability to absorb water in times of flooding and slowly release it in times of drought (United States Environmental Protection Agency [EPA], 2001). If we had more wetlands on the landscape and near our communities flooding and the damage it causes, could be reduced. The possibility of using wetlands for this purpose poses two main questions: how do we get more wetlands, and is it economically viable?

Wetland Restoration

Fixing Pre-Existing Wetlands

Increasing how many wetlands we have on the landscape and near our communities, has a simple solution: fix the pre-existing wetlands that have been degraded. Roughly 35% of the world’s wetlands were lost from 1970 to 2015 and the destruction of wetlands has only increased in the 2000s (United Nations Climate Change, 2018). Canada alone has lost 65% of our Atlantic coastal marshes, 80–98% of wetlands within or adjacent to Canada’s urban centres, 68% of wetlands that were once present in southern Ontario, over half of the central prairie potholes, and 70% of our Pacific estuary marshes (Canadian Wildlife Service, 1991). It is obvious that there is a lot of room for improvement and many areas where we could increase our number of wetlands.

Cost

The cost of wetland restoration can vary widely. The Interim Guidelines for Wetland Protection and Conservation in British Columbia estimate most wetland restoration projects cost between USD 1,000/ha and USD 124,000/ha (Wetland Stewardship Partnership, 2009). One specific project proposed in the Kootenay area of B.C. has an average cost of USD 55,369.44/ha (Biebighauser & Annschild, 2016). In return, such a wetland could prevent USD 5,700/ha per year in flood damages (Ming et al., 2007). Within 10 years, the wetland would pay for itself, and within 20 years, the wetland would mitigate an extra USD 58,630/ha in flood damages (see Table 1).

Table 1: Payoff of Restored Wetland Under Different Social Discount Rates (USD/ha)

Note. Calculations made using data from Ming et al. (2007).

Flood Mitigation

With the continuous rise of global temperatures, the flood mitigation services of wetlands will become more important than ever. Under the Representative Concentration Pathway 8.5, extreme precipitation events are expected to increase in frequency by two to five times by the end of the century (Alfieri et al., 2017; Swain et al., 2020). In Middlebury, Vermont, Otter Creek floodplains and wetlands were estimated to have prevented 84–95% of damages from Tropical Storm Irene, which equates to upwards of $2,000,000 (Watson et al., 2016). If such a storm happened historically once in 100 years, in the future, one like it may occur once every 50 or even once in 20 years. If these types of storms happen once in 50 to once in 20 years, within 100 years, the Otter Creek floodplains and wetlands would save the residents $4,000,000 to $10,000,000 in damages, on top of the yearly normal flood mitigation.

Conclusion

The ability of wetlands to mitigate flood damage from both common and extreme precipitation events is valuable. Our changing climate will only increase our need for the services wetlands can provide. Restoring a wetland is an investment for a community and can be an important tool for adapting to climate change.

Media Attributions

Figure 1: “Figure 1: Pond and wetland at Albert McGowan Park” by Arwinddeep Kaur, via A Study of the Value of Kamloops Parks (Tsigaris, et al., 2022) is used under a CC BY-NC-SA 4.0 license.

Figure 2: “Pond and wetland at Albert McGowan Park photo” by Panagiotis Tsigaris (2024) is used under a CC BY-NC-SA 4.0 license.

References

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Tsigaris, P. (2024). Pond and wetland at Albert McGowan Park photo [Image].

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