As Harrison eyes flood wall, some worry about impact on views

Harrison Hot Springs is considering raising its 77-year-old dike and building a flood wall. If approved, the moves could help the community avoid a future flood—but also significantly change the look of the village’s familiar lakefront.

The village’s dike should be raised by more than one metre in order to protect against a major flood event, engineer Daniel Maldoff told council at a recent meeting at which a design for the project was presented.

The engineers recommend raising earthfill dikes in front of the Harrison Hot Springs Resort and Rendall Park. (Earthfill dikes are made up of multiple layers of rock and soil.) 

That would bring the dike up to provincial standards and create a barrier that would be a metre higher than the largest flood on record.

But it may still not be enough to save the community from a natural disaster. Maldoff warned council that high waves could still allow water to enter the village during a major flood event, and future adaptations may be required due to climate change. 

“You would see some overtopping and that water would need to be managed on land,” he said. 

There are three different flood hazards in Harrison: a freshet from the Fraser River that causes the lake level to breach its banks; localized flooding resulting from fall and winter storm weather; and a tsunami caused by a landslide on Mount Breakenridge that could create a wave up to 25 metres high in Harrison Lake. 

The original dike was built following the 1948 Fraser River flood that inundated the village and communities across the valley. 

Although the dike’s crest was built a metre higher than the levels seen in 1948, it isn’t high enough to protect against a flood like the mammoth event that swamped the Fraser Valley in 1894. And climate change is making both moderate and major floods more likely. In 2022, council received a report that said the village should raise its dike by more than a metre. (Fully protecting against a tsunami would require a flood barrier.) 

Harrison has since received $11 million in grants—from the province and Union of BC Municipalities (UBCM)— to upgrade the dike.

The plans also include revamps to the waste water treatment plant, which is located on the west side of the lakeshore. Under initial designs, the access road to the plant would be raised by more than two metres to prevent erosion. 

About 15 to 20% of the grant funding is expected to go to that part of the project 

A ‘flood wall’

The most significant change may be to the heart of the village. 

It’s not possible to extend the earthfill dike across the Harrison Lagoon and main waterfront because of “footprint constraints,” according to Maldoff. He suggested building a 1.1 metre-high permanent flood wall to get that portion of the flood barrier in line with provincial standards. 

If constructed, the wall would stretch from the Harrison Hot Springs Resort to Rendall Park and include multiple openings. Permanent barriers would be anywhere from 17 to 112 metres long, with spaces in between ranging from 10 to 40 metres to preserve lakefront views. 

In emergencies, the openings could be plugged by temporary barriers like stoplogs, flexible tubes, muscle walls, or another geotechnical barrier. A final decision on the precise temporary barrier to be used has not yet been made. Each option has different costs and structural limits, which were not unveiled in the presentation.

The flood wall designs were based on a similar project that is currently underway in Calgary. 

Village council expressed concerns that the wall would infringe on views. 

Modelling historic flood impacts

Coun. Mark Schweinbenz also questioned the barrier’s role if floodwaters approached Harrison from the south, rather than from the lake. The report noted that a Fraser River flood that breached dikes south of Agassiz could inundate the entire village. 

A recent study shows that a massive breach of the Kent dike could flood the community within hours. 

A 2023 simulation suggests that a flood event like that which occurred in 1894 could topple the upstream portion of the Kent dike and allow water to flow north, up the Harrison River, and into Harrison Hot Springs. 

In that scenario, flooding would continue for several days. Most of the lower Fraser floodplain would be under a metre or more of water. In some areas, the water could be up to seven metres deep. Floodwaters would not start to recede for more than one week after the initial breach, making it difficult to assess the total damage for days, according to the simulation.

Schweinbenz urged the province to come up with a regional dike solution to prevent flooding from the Fraser River. 

“We could have the best wall installed for $11 million and the south end of our village still gets flooded,” he said. “It’s not going to solve the issue long term.” 

Preserving views

Mayor Fred Talen reiterated that the village doesn’t want to block views of the lake or the surrounding mountains. He’s eager to hear public feedback on the project. 

“Ideally, I’d like to press a button somewhere in the council chambers and have the whole thing lift up like James Bond, but I think that’s beyond the budget or technology,” Talen said. 

The village is expected to seek public input on the view corridors and temporary barriers. 

The project is expected to be completed in 2027.