The flood mitigation carried out at the Calgary Zoo protects the zoo from overland flooding of the Bow River. We installed a steel sheet-pile cofferdam wall around the perimeter of St. George's Island and dewatering system within the zoo to manage interior groundwater levels at flood-prone times of the year.

With no formal guidelines and little technical literature to support the design of such specialized flood-mitigation infrastructure, the project team turned to engineering fundamentals to develop a unique solution to protect the Calgary Zoo from a future disaster. The one-of-a-kind design sensitively integrates the flood-mitigation structures with the zoo’s buildings and structures, while complementing and enhancing the zoo’s heritage, identity and aesthetics and allows for future expansion.

A hydrogeological study carried out at the confluence of the Bow and Elbow Rivers informed the design and advanced The City’s understanding of groundwater flow and underground flooding, which will enhance future flood mitigation planning throughout Calgary. Before resources were fully mobilized, PCL conducted a pilot program that tested the limitations and advantages of the proposed sheet pile system. The program confirmed that the team would be able to drive the steel sheets through the coarse river cobbles and boulders and get a watertight seal at the level of the bedrock. The use of sheet piles for the structure minimized loss of essential riparian habitat, floodway encroachment and zoo property at the edge of the island. 

It is Calgary Zoo’s priority to preserve mature trees. In the few cases where removing a tree was truly unavoidable, the removed trees were incorporated within zoo exhibits or repurposed as bioengineered fish habitat along riverbanks in other parts of the city.

The Zoological Society knows they have a secure system to protect infrastructure, exhibits and animals from a 1-in-100-year flooding of the Bow River. Flood mitigation was done within an extremely small footprint that ensured uninterrupted continuity for zoo access and operations and minimal disruption to neighbors, zoo visitors and animal residents. The local community and neighborhood can also enjoy over 500 meters of new walkways and landscaping along the river’s edge.