Small Scale Residential Stormwater Management

Housing types in Coquitlam continue to evolve to meet the needs of our community. Historically, Coquitlam was mostly single-family homes with grass lawns—absorbent areas—that allowed rainfall to absorb directly into the soil. Current development practices now include larger building footprints and more hardscape areas such as sheds, patios and driveways.

The Province has recently (2024) adopted Provincial Housing legislation (Bill 44) which simplifies development of small-scale multi-unit housing (SSMUH). This approach allows a streamlined process to create multiplex units within existing single-family lots. More than 30% of Coquitlam’s land is composed of low-density residential area, which will be significantly impacted by these legislation changes.  

Small-scale residential development supports housing supply but also increases hard surfaces, which disrupts the natural water cycle—continuous movement of water on, above and below the ground—by decreasing the ability for rainwater to absorb into the ground on-site. This increases stormwater runoff that ultimately releases into our creeks and rivers. Coquitlam is home to over 300 kilometers of creeks and streams that provide fish habitat and other benefits to the community. They are important for local drainage, flood mitigation, air quality improvement and temperature regulation. These natural water bodies also provide residents with natural green space to support their physical and mental well-being. 

Increasing stormwater runoff can result in erosion in creeks and impact groundwater recharge that contributes to summertime creek, base flow. Hardscape areas have pollutants such as sediment, oils, fertilizer, heavy metals and other debris that gets transported by the runoff into our creeks. This has negative impacts on the creek’s water quality and aquatic life. 

By managing stormwater runoff at the source, we can reduce the likelihood, frequency and intensity of erosion downstream, lower water temperatures and improve water quality. On-site stormwater management for small-scale residential developments is a critical step in reducing our impact on the natural environment. Everyone plays a part in protecting these important natural watercourses.

Small-scale developments as defined in the building bylaw, must prepare an on-site stormwater management plan. Applicants may select between two design approaches: use of City Standards or a Customized Stormwater Management Plan.

• City Standards reduces application complexity and aims to minimize costs for applicants. 
• Customized Stormwater Management Plan allows for greater flexibility when standard designs are not feasible or appropriate for the site. 

Refer to the 'Stormwater Management Design Guidelines and Criteria for Small-Scale Development' for the complete small scale development on-site stormwater management requirements.

Regardless of the approach, all applicants must consider key site constraints. 

• Detention-only—temporary storage—will be required for properties located on steep slopes as identified in the Steep Slope Map. 
• In areas with a high groundwater table—within 1.2 meters of the ground surface—a customized plan is required.

For more information on which approach is suitable, review the Small-Scale Residential Stormwater Management Form, which must be submitted with the building permit.