Abstract Manager

The recovery from the 2021 Atmospheric River Event (ARE) in BC, provided an opportunity to rethink traditional engineering approaches to mitigate scour and erosion of road embankments adjacent to watercourses, with a focus on the integration of environmental benefits into the project development life cycle. This case presents the successful implementation of the recovery of Othello Road, located near Hope, BC.

The Coquihalla River eroded the right bank for a length of 550m, shifting its course north by 125m and adjacent to Othello Road, leaving this section of the road exposed to further risk of erosion.

Shifting away from traditional riprap embankment protection, through a collaborative effort between civil, hydrotechnical, and environmental disciplines, we explored an alternative approach consisting in the construction of four groynes, protruding into the wetted width of the river. These groynes achieve multiple design goals:

1. Shifting the high velocity flow away from the road embankment, leading to less riprap required (estimated a saving of 10,000m³ of riprap)
2. Creating low velocity zones on the backside of the groynes through the integration of anchored large woody debris with root wad, boulder clusters and log jams, providing valuable rearing and potential spawning habitat for the aquatic wildlife.
3. Providing additional footprint that supported the groyne revegetation effort, when compared to a traditional approach and existing conditions. The design included the revegetation of ~0.4ha and planting of more than 4,500 native trees and shrubs, with a net positive gain.

To achieve success in this project the design team had to face different challenges:

• Obtain Federal and Provincial regulatory approvals, requiring engaging early and often with intensive coordination with all levels of permitting agencies to demonstrate the net environmental gains that this approach would provide.
• An aggressive design, tender, and construction schedule, required to complete a temporary river diversion to allow construction activities within the active riverbed during the short regional window of least risk for fish and wildlife.
• The selection of a specific soil mix capable of resisting washout during high-flow events or heavy rainfall, while being conducive of the revegetation efforts.

This project is a testament of how integrating environmental key aspects in the early design phases, rather than being an afterthought, can benefit the overall project delivery by meeting all engineering and environmental goals, schedule, and resulting in significant cost savings.