Vancouver's Rain City Strategy — A 90% Rainfall Target and a Doubled 48 mm Design Standard on Public and Private Land (Canada)

In November 2019 Vancouver City Council adopted the Rain City Strategy with Streets & Public Spaces and Buildings & Sites action plans, implementation targets and a rainwater management design standard. It builds on the city's earlier performance target of managing 90% of average annual rainfall.
The strategy doubles the required design standard for the rainwater volume managed by sites and green rainwater infrastructure (GRI) assets from 24 mm to 48 mm per day, in both public and private spaces, and sets an implementation target to manage rainwater volume and water quality for 40% of the city's impervious areas by 2050 through new development, capital and renewal projects and strategic retrofits. GRI includes rain gardens, green roofs, blue-green roofs and permeable pavements.
Before the strategy the city reported more than 240 GRI assets in its streets, plus many in parks and other public spaces. Aims are fewer combined-sewer overflows, less urban flooding and better water quality in receiving waters.
Evidence caveat: the sources document the targets, standards and policy design, not independently measured basin-scale runoff or water-quality outcomes, and the 2050 target depends on redevelopment and retrofit rates. It is included as a transferable governance model rather than a proven-outcome case.

Read the full analysis: https://council.vancouver.ca/20191105/documents/rr1a.pdf