Close-up of permeable pavement with interlocking concrete pavers and grass growing through the gaps, demonstrating sustainable urban infrastructure.

Climate adaptation and rainwater management

What you need to know

We’re working on advancing rainwater management and other climate adaptation objectives on private property using green rainwater infrastructure (GRI).

Our goals are to:

Improve water quality
Make our city more resilient
Enhance livability

GRI mimics the natural water cycle by using plants, soils, trees, and built structures to capture and clean rainwater where it lands before returning it to our environment.

GRI provides other co-benefits, such as supporting biodiversity and reducing urban heat, and plays an important role in supporting many of our key strategies.

GRI practices on private property

Overview of grey and green rainwater infrastructure (GRI)
Co-benefits of GRI
Related by-laws, strategies, and other resources

Learn more about rainwater management requirements on private property.

Our GRI strategies extend to public spaces. Find out what we are doing on streets and boulevards

Overview of grey and green rainwater infrastructure (GRI)

Our challenges with urban growth

Before development

The city was once covered by a forest that supported a natural water cycle. Rainwater soaked into the ground, was absorbed by trees, or flowed through streams to the inlets and the Fraser River.

Changes with development

As the city expanded, we cleared trees and constructed sewer pipes, roads, sidewalks, and parking lots. These changes reduced the ground's ability to absorb rainwater.

Changes to the water cycle

Today, there is less rainwater flowing into the ground and more flowing along the surface.

Impacts on the environment

Rainwater collects pollutants as it flows from rooftops and streets into our sewers. In Vancouver, storm water and sewage are carried together in certain pipes. During heavy rains, these pipes can overflow, causing combined sewer overflows (CSOs). This results in untreated sewage and polluted rainwater entering our rivers and inlets, which lowers water quality and harms aquatic life.

Challenges with climate change

As the climate gets warmer and the city continues to grow, these environmental problems will get worse. We need to find ways to handle more rainwater and protect our natural habitats.
How green rainwater infrastructure works
GRI tools like green roof systems and ground infiltration systems (rain gardens) are designed to mimic the natural water cycle.

GRI use natural elements such as plants, soils, trees, and built structures to:
- Capture and clean rainwater where it lands
- Return the cleaned rainwater to the air, soil, and groundwater, or allow it to flow back to waterways and inlets
- Harvest and reuse rainwater for other purposes
Learn more about green roofs and water reuse systems.
How rainwater detention and retention work in grey infrastructure and GRI
Pipes and other grey infrastructure move rainwater and sewage away from private property. Sometimes this involves rainwater 'detention'.

GRI systems like green roofs and natural assets like trees and plants also use rainwater 'retention'. The use of this water has many co-benefits, and may delay the need for grey infrastructure upgrades.

Rainwater detention

This occurs when water is held back and later released. It slows down water but does not change the amount of water released into the sewer system.

Examples of how water is detained:
- Soils
- Green or blue-green roof growing medium
- Blue-green roof shallow water reservoir
- Detention tank (may also be used with a green roof)
Rainwater retention

This occurs when water is used for another purpose. It reduces the amount of water leaving a site and released into the sewer system.

Examples of how water is retained:
- Releasing into the air (evaporation)
- Seeping into the ground
- Used by trees and plants (transpiration)
Roles of grey and green rainwater infrastructure
Different kinds of rainwater management tools are best suited to handle different types of rainfall events.

Types of rainfall

Vancouver experiences 3 main types of rainfall annually:
- Light showers, which make up 70% of the rainfall
- Rainstorms, accounting for 20%
- Extreme rainstorms, comprising 10%
Rain City Strategy goals

The Rain City Strategy (21 MB) aims to manage 90% of Vancouver's average annual rainfall using GRI.

Types of rainfall managed by GRI and grey infrastructure

While GRI can be used to manage light showers and some rainstorms, there will always be a role for the city’s ‘grey’ sewer system to manage extreme rainstorms.

Learn more about the types of rainfall managed by GRI and grey infrastructure (88 KB)