2024 Track 1 Day 2: Humes


Green Rainwater Infrastructure (GRI) Performance Monitoring in the City of Vancouver


The Rain City Strategy, adopted by the City of Vancouver Council in 2019, provides a long-term roadmap for progressing and evolving our rainwater management practices and services in the City of Vancouver.

The Rain City Strategy has set out ambitious targets to capture and clean 48mm of rainfall over a 24h period and manage urban rainwater runoff from 40% of impervious areas in the city by 2050. In order to achieve these targets, Green Rainwater Infrastructure (GRI) is being implemented across the City.

GRI uses a suite of technologies such as bioswales, rainwater tree trenches and subsurface infiltration that mimic the natural water systems in an urban environment.

These systems function by capturing rainwater runoff, treating it and allowing it to infiltrate back into the ground close to where it landed and in the process, diverting large amounts of runoff from our sewer systems. But once they are built, how do we determine if they are meeting their performance objectives?

We monitor GRI assets using a variety of methods including water level monitoring, soil monitoring, flow monitoring, and water quality monitoring in order to assess their performance. This presentation will focus on the GRI monitoring program and the findings for the last several years of monitoring and the lessons learned along the way.

Results from our monitoring program show that our systems are draining quickly, with drawdown rates much higher than the measured field infiltration rates prior to construction. We also see that plants within these systems can stay healthier over the long dry summer period, due to the additional soil moisture from rainwater

Synthetic runoff tests have shown that our bioretention systems are effective in reducing up to 75% of the volume of rainwater runoff going to our sewer systems and providing water quality benefits (99% TSS mass reduction).


Cassandra Humes

Cassandra Humes, City of Vancouver

Cassandra Humes is a Monitoring Technician with the Green Infrastructure Implementation Branch at the City of Vancouver. She has experience in environmental monitoring in both the private and public sector. She is responsible for overseeing the day-to-day activities of the GRI monitoring program.