SR1 will have a significant impact on flood flows along the Elbow River. It will also reduce flood flows on the Bow River downstream of the confluence with the Elbow, but the effect will be less on the Bow River than on the Elbow. Though the flood hazard area will shrink, regulation in areas with upstream mitigation must consider:

• Risk from groundwater during or after high flow events (the groundwater table rising and potentially entering basements, even if water doesn’t flow over the bank)
• Risk from overland flooding for flood events larger than the reservoirs can handle. The combination of SR1 and the Glenmore Dam will protect from overland flooding up to a 2013 flood level.
• Increasing flood severity due to climate change.
• Other impacts on the health of riparian areas no longer governed by flood hazard restrictions (bank erosion, fragmentation and loss of habitat, etc.).

SR1 and the Glenmore Reservoir together will mitigate overland flooding up to a 2013 level flood for flood risk for communities along the Elbow River.

Upstream flood mitigation infrastructure, like SR1, are critical investments for reducing Calgary’s flood risk and it is important that our flood risk mapping reflects this.

Equally, it is important that we consider what planning tools and regulations should continue to apply, to support public safety, minimize property damage, protect the river environment and enable flood and climate resilient community growth.