Coastal modelling and nature-based solutions protect Haida Gwaii’s vital transportation routes

Located off British Columbia’s northern Pacific Coast, Haida Gwaii is an archipelago consisting of two main islands, Graham Island in the north and Moresby Island in the south, along with approximately 400 smaller islands. The ancestral lands of the Haida Nation, the history of Haida Gwaii dates back thousands of years. Living along coastal waters, historically, Haida People used canoes as their primary mode of transportation.

Today, Highway 16 and Alliford Bay Road form the main transportation route connecting Sandspit in the south to Daajing Giids and Skidegate, Tlell, Port Clements, and Masset in the north. There are no alternate routes between communities for transporting goods or emergency services. These critical roads parallel the coastline and frequently experience coastal erosion as a result of storm events in Hecate Strait.

The BC Ministry of Transportation and Transit retained Associated Engineering to serve as the prime consultant to complete the Haida Gwaii Shoreline Protection Study to identify areas along the road with high erosion potential and present conceptual design options to mitigate impacts to the roadway and keep the residents connected. The study included frequent communication with local governments and the Haida Nation for their input and feedback.

Technical undertakings included comprehensive site reconnaissance, metocean (meteorology and oceanography) condition analysis, spectral wave modelling, shoreline classification, and a spatial assessment of the proximity of infrastructure to the shoreline. Project Manager and Technical Lead, David Forde, tells us, "These efforts informed the development of a vulnerability matrix, which revealed that much of the project area faces medium-to-high vulnerability to coastal erosion."

The assessment is corroborated by the near-annual repairs undertaken by the Ministry along the highway. Six segments identified as highly vulnerable were selected and conceptual stabilization designs were developed to address these critical areas.

Wherever possible, the proposed concepts emphasize nature-based solutions. Some of the options included rock headlands and self-distributing sand nourishment, in addition to traditional revetments

Due to a balance of the high wave energy, material cost and availability limitations, and importance of preserving natural environment, a hybrid of these options is recommended.

Associated is continuing to work with the Ministry on a separate assignment to refine estimates, review material availability, and further quantify risks. Together with the Ministry and our project partner, DHI Water and Environment, Associated intends to prepare designs to inform coastal erosion protection at pilot sites. We hope these pilot sites will provide valuable ‘lessons-learned’, which can be leveraged in the design and protection of high-vulnerability segments along this critical transportation corridor.

Associated Engineering's key project members included David Forde, Chloe Sirges, Nicola Van Der Mark, and Josh Holland.