Sydney's Climate Challenge: Heat, Floods, and a City Adapting

Sydney's climate risks are concentrated in two domains: extreme heat that is intensifying in the western suburbs as the urban heat island effect compounds regional warming, and intense rainfall events that periodically overwhelm the stormwater and drainage infrastructure of a city built for a climate that is already becoming history. Both hazards have been experienced in severe form in recent years, and both are expected to intensify under projected warming scenarios.

Western Sydney suburbs including Penrith, Richmond, and the outer western growth corridor experience temperatures during summer heat events that consistently exceed eastern Sydney and coastal readings by five to ten degrees, a differential that reflects the interaction of urban surfaces, reduced canopy cover, and the distance from the cooling influence of the ocean. The health consequences of this heat differential fall disproportionately on lower-income communities with less access to air conditioning and outdoor cooling infrastructure.

The March 2021 floods, the worst in the Hawkesbury-Nepean Valley in decades, demonstrated the flood vulnerability of communities that have developed on the floodplains of the river system west of Sydney. The subsequent review of flood management strategies, including the role of the Warragamba Dam wall raising in moderating downstream flood peaks, generated one of the most contested infrastructure policy debates in NSW in recent years.

The Sydney metropolitan catchment's water supply, managed through Warragamba and the supporting Upper Nepean system, has received above-average inflows during the La Nina years that have followed the severe drought of 2017-2019. Storage levels returned to comfortable levels but the drought demonstrated the system's vulnerability to extended dry periods that climate projections suggest will become more frequent rather than less as warming continues.

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