Probable maximum flood in a changing climate: An overview for Canadian basins

- An approach to include climate change to compute PMP and PMF with RCMs is proposed.
- Projected increases in spring PMP except for the most northern basin.
- Projected change in spring PMF ranges from −1.5% to 20% for all basins.
- Future PMFs can be accommodated by existing infrastructure and operating rules.

Study Region: In Canada, dams which represent a high risk to human loss of life, along with important environmental and financial losses in case of failure, have to accommodate the Probable Maximum Flood (PMF). Five Canadian basins with different physiographic characteristics and geographic locations, and where the PMF is a relevant metric have been selected: Nelson, Mattagami, Kénogami, Saguenay and Manic-5.Study Focus: One of the main drivers of the PMF is the Probable Maximum Precipitation (PMP). Traditionally, the computation of the PMP relies on moisture maximization of high efficiency observed storms without consideration for climate change. The current study attempts to develop a novel approach based on traditional methods to take into account the non-stationarity of the climate using an ensemble of 14 regional climate model (RCM) simulations. PMPs, the 100-year snowpack and resulting PMF changes were computed between the 1971-2000 and 2041-2070 periods.New Hydrological Insights for the Region: The study reveals an overall increase in future spring PMP with the exception of the most northern basin Nelson. It showed a projected increase of the 100-year snowpack for the two northernmost basins, Nelson (8%) and Manic-5 (3%), and a decrease for the three more southern basins, Mattagami (-1%), Saguenay (-5%) and Kénogami (-9%). The future spring PMF is projected to increase with median values between -1.5% and 20%.