Rainfall in Metro Vancouver will be up to 45% more intense by 2050: report

A car damaged in a flooded parking lot in downtown Vancouver on October 28, 2018. (Nicolas Andre Guaiquin / submitted)

‘Raincouver’ will have an intensified meaning over the coming decades.

A recent report by Metro Vancouver Regional District, assessing the impact of climate change on local rainfall and stormwater infrastructure, predicts a troubling future.

Rainfall will significantly intensify due to climate change in “all scenarios,” with rainfall becoming 20% to 45% more intense by 2050 and 40% to 75% more intense by 2100.

Intense rainfall events will occur more frequently as the effects of climate change become more apparent. The increases are averaged over the entire region and averaged over different types of storms with durations between five minutes and 24 hours.

While the current one-in-100-year event is a large rainstorm that currently has a 1% probability of happening in any year, such an event of the same size may eventually become the one-in-12-year event or the one-in-six year event by 2100 in the moderate and high scenarios, respectively.

The Regional District projects major new infrastructural investments will be required to deal with future rainfall increases on sewerage and drainage functions.

“Current levels of service for sewerage and drainage systems cannot be maintained by current infrastructure in the future climate,” reads the report.

“Decisions are needed whether increased localized flooding will be acceptable, compared to the costs of adaptation to protect infrastructure and buildings against increasing flood risks. Adaptation responses include hardening and protecting, gradually upgrading, or accepting lower levels of service. These involve tradeoffs between cost, flexibility, and risk.”

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