To better manage stormwater, Vancouver, B.C., transforms streets into ‘blue green systems’
August 21, 2023
As part of its first blue green system, Vancouver modified an eight-block stretch of Richards Street in the city’s urban core. As part of the project, a parking lane was converted into a grade-separated bike lane and stormwater tree trenches that were designed to accept runoff from inlets, catch basins, and permeable pavers. Credit: City of Vancouver/Shannon Mendes
By the end of next year, the City of Vancouver, British Columbia, Canada, expects to complete the second of what it calls “blue green systems.” A combination of green infrastructure and traffic calming measures, blue green systems represent one of Vancouver’s key approaches for managing stormwater and greening the city’s urban fabric.
‘Making room for water’
“Blue green systems are networks of connected park-like streets that manage water and land in a way that is inspired by nature and designed to replicate natural functions and provide ecosystem services,” according to the description of the practice on the City of Vancouver’s website. “These systems seek to protect the ecological, hydrological, and social values of the urban landscape and water cycle, and to provide resilient measures to address climate change and flood management, increase connectivity, and enhance access to nature.”
After interviewing comparable peer cities around the world, Vancouver “landed on this idea of making room for water and respecting and making the best use of a valuable resource,” says Cameron Owen, a senior watershed planner for the city. As a result, Vancouver “included the idea of blue green systems as a key action item in the Rain City Strategy five years ago,” he notes.
Vancouver’s Rain City Strategy outlines a series of actions to improve water quality, increase resilience to climate change, and enhance city ecosystems using natural infrastructure. Objectives identified in the strategy include removing pollutants from water and air, increasing managed impermeable areas, reducing the volume of rainwater entering the sewer system, harvesting and reusing water, mitigating the urban heat island effect, and increasing the total green area within the city.
Capturing stormwater flows
Pursuant to this strategy, Vancouver began analyzing its major drainage networks and comparing that to data on overland flooding in the city. “What we've found was that there was a really interesting pattern in which the blue green systems follow essentially where there were historically streams in the city,” Owen says.
Although many of Vancouver’s streams were encased in underground pipes long ago, water on the city surface “still approximates those historic waterway pathways,” Owen notes. Meanwhile, the city also discovered a “strong connection” between the historic water routes and areas in which the city sought to improve ecological conditions and connect green spaces, he says.
A key goal for blue green systems is to “intercept and disrupt” stormwater flows “before they make it to lowland areas” that increasingly are susceptible to flooding during large rain events, Owen says. “The strategy was to try, in a systematic way, to pick off some of those flows, manage the water in upland areas where possible, delay it, and soak it back into the ground.”
In developing its blue green systems strategy, Vancouver aims to meet multiple goals, such as managing stormwater capacity in its drainage system, adding green spaces, connecting biodiversity corridors, and improving access for pedestrians and cyclists. Meeting these goals requires adding a host of facilities within the right-of-way along segments of selected streets. “It's really a lot of green infrastructure,” Owen says. Bike lanes and pedestrian-only areas also are included as part of blue green systems.
More than 100 trees were planted as part of the Richards Street blue green system to take up rainwater through their roots and promote infiltration into the soil. Credit: City of Vancouver
Vancouver’s first blue green system
Vancouver completed its first blue green system in fall 2021, when it modified an eight-block stretch of Richards Street in the city’s urban core. As part of the project, a parking lane was converted into a grade-separated bike lane and stormwater tree trenches that were designed to accept runoff from inlets, catch basins, and permeable pavers. More than 100 trees were planted as part of the project to take up rainwater through their roots and promote infiltration into the soil.
To complement the bike lane, public bike share stations and bike racks also were added. The green infrastructure elements were internally designed and constructed, led by the city’s Green Infrastructure Implementation branch.
Among its ecological benefits, the Richards Street blue green system is expected to sequester nearly 51,000 kg of carbon dioxide during the next 50 years, according to a project fact sheet from the city. By managing runoff from 1.1 hectares of impervious area, the project annually treats approximately 15 million liters of urban rainwater onsite and diverts 11 million liters of runoff from the sewers.
A rendering of the St. George Rainway Credit: City of Vancouver
The next blue green system
Vancouver’s next blue green system — the St. George Rainway — is a multiphase project located along St. George Street between 5th Ave. and Kingsway. Work began earlier this year on the first phase of the project, which will manage rainwater along four blocks, between 5th Ave. and Broadway. Construction is expected to be completed by the end of 2024.
“It's a multiblock green infrastructure project,” Owen says. Like the Richards Street project, the St. George Rainway will convert a parking lane into stormwater management features. A series of meandering rain gardens along the east side of the street will collect rainwater in planted areas and provide gathering spaces. Within the rain gardens, corten steel check dams will slow the flow of water and help promote infiltration, while layers of gravel and rock will provide underground storage.
Street trees and other plantings will add habitat, increase shade, and facilitate stormwater management. A bikeway and car-free zones will provide safe spaces for cyclists and pedestrians, while improved sidewalks and ramps will aid accessibility. Additional amenities will include plazas with seating and public art.
Multiple benefits
A driving force behind the project was a desire on the part of the local community to improve environmental conditions and acknowledge the presence of a historic stream that passes through the site in an underground conduit. In essence, the St. George Rainway helps to “deliver this community aspiration for a greener street with more water and more green and leafy expression,” Owen says.
At the same time, the stormwater management features will help to manage capacity and delay the need for upgrades in the combined sewer system serving the area. “From a drainage management point of view, there were a lot of reasons in this combined sewer catchment to lump on as much green infrastructure as possible,” Owen says. “Green infrastructure was the more cost-effective path forward.”
The St. George Rainway also will “help address some of the urban heat island effects that we see,” Owen says. “As we do our planning work, we try to make sure that we're providing urban forests to shade our pervious surfaces, to systematically close gaps in the urban forest, especially in historically underserved communities. Then use that to help guide some of our capital planning work.” The project is expected to cost between CAD $4 million and CAD $6 million (USD $3 million and USD $4.4 million) to design and construct.
More systems planned
Vancouver has plans for additional blue green systems, including one on Alberta Street in the vicinity of Columbia Park. “That project is still in the concept development phase,” Owen says.
Funding for the blue green systems, as well as other green infrastructure added by Vancouver, comes from the utility development cost levy that the city assesses developers on a per square foot basis for their projects. However, the city also has received grant funding to be used for green infrastructure from the Natural Infrastructure Fund program overseen by the Canadian government.