Human Influence on the 2021 British Columbia Floods

48 Pages Posted: 3 Feb 2022 Last revised: 29 May 2022

See all articles by Nathan Gillett

Nathan Gillett

Environment and Climate Change Canada

Alex Cannon

Environment and Climate Change Canada

Elizaveta Malinina

Environment and Climate Change Canada

Markus Schnorbus

University of Victoria

Faron Anslow

University of Victoria

Qiaohong Sun

University of Victoria

Megan Kirchmeier-Young

Environment and Climate Change Canada

Francis Zwiers

University of Victoria

Christian Seiler

Environment and Climate Change Canada

Xuebin Zhang

Environment and Climate Change Canada; Environment and Climate Change Canada

Greg Flato

Environment and Climate Change Canada

Hui Wan

Environment and Climate Change Canada

Guilong Li

Environment and Climate Change Canada

Armel Castellan

Environment and Climate Change Canada

Abstract

A strong atmospheric river made landfall in southwestern British Columbia, Canada on 14th November 2021, bringing two days of intense precipitation to the region. The resulting floods and landslides led to the loss of at least five lives, cut Vancouver off entirely from the rest of Canada by road and rail, and made this the costliest natural disaster in the province's history. Here we show that westerly atmospheric river events of this magnitude are approximately one in ten year events in the current climate of this region, and that such events have been made at least 60% more likely by the effects of human-induced climate change. Characterized in terms of the associated two-day precipitation, the event is approximately a one in 50-100 year event, and its probability has been increased by a best estimate of 50% by human-induced climate change. The effects of this precipitation on streamflow were exacerbated by already wet conditions preceding the event, and by rising temperatures during the event that led to significant snowmelt, which led to streamflow maxima exceeding estimated one in a hundred year events in several basins in the region. Based on a large ensemble of simulations with a hydrological model which integrates the effects of multiple climatic drivers, we find that the probability of such extreme streamflow events has been increased by human-induced climate change by a best estimate of 2 to 4. Together these results demonstrate the substantial human influence on this compound extreme event, and help motivate efforts to increase resiliency in the face of more frequent events of this kind in the future.

Keywords: Event attribution, atmospheric river, extreme precipitation, streamflow, British Columbia, flooding

Suggested Citation

Gillett, Nathan and Cannon, Alex and Malinina, Elizaveta and Schnorbus, Markus and Anslow, Faron and Sun, Qiaohong and Kirchmeier-Young, Megan and Zwiers, Francis and Seiler, Christian and Zhang, Xuebin and Flato, Greg and Wan, Hui and Li, Guilong and Castellan, Armel, Human Influence on the 2021 British Columbia Floods. Available at SSRN: https://ssrn.com/abstract=4025205 or http://dx.doi.org/10.2139/ssrn.4025205

Nathan Gillett (Contact Author)

Environment and Climate Change Canada ( email )

Gatineau
Canada

Alex Cannon

Environment and Climate Change Canada ( email )

Gatineau
Canada

Elizaveta Malinina

Environment and Climate Change Canada ( email )

Gatineau
Canada

Markus Schnorbus

University of Victoria ( email )

3800 Finnerty Rd
Victoria, V8P 5C2
Canada

Faron Anslow

University of Victoria ( email )

3800 Finnerty Rd
Victoria, V8P 5C2
Canada

Qiaohong Sun

University of Victoria ( email )

3800 Finnerty Rd
Victoria, V8P 5C2
Canada

Megan Kirchmeier-Young

Environment and Climate Change Canada ( email )

Gatineau
Canada

Francis Zwiers

University of Victoria ( email )

3800 Finnerty Rd
Victoria, V8P 5C2
Canada

Christian Seiler

Environment and Climate Change Canada ( email )

Gatineau
Canada

Xuebin Zhang

Environment and Climate Change Canada ( email )

Gatineau
Canada

Environment and Climate Change Canada ( email )

Gatineau
Canada

Greg Flato

Environment and Climate Change Canada ( email )

Gatineau
Canada

Hui Wan

Environment and Climate Change Canada ( email )

Gatineau
Canada

Guilong Li

Environment and Climate Change Canada ( email )

Gatineau
Canada

Armel Castellan

Environment and Climate Change Canada ( email )

Hull, Quebec K1A 0H3
United States
2505088058 (Phone)

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