Calm summer waves lap at the idyllic crescent of white sand on Calvert Island’s West Beach. At the back of the beach, windblown Sitka spruce form a botanical wall, separated from the gently sloped beach by sand dunes. A few grains of sand blow along the shore, but the five-meter-high dunes appear solid. Hidden up in the trees, time-lapse cameras reveal a much different story.
Hakai researcher Derek Heathfield set up three cameras late last summer at different points along West Beach. Once every fifteen minutes, the cameras snap a photo of the beach from the same, fixed position.
He returned six months later, this past April, to retrieve the photos. The changes to the beach are drastic. The dunes are unrecognizable shadows of their former selves—as if the Rockies had turned into the Appalachians in a few months.
By March, the seaward face of the dune has been sculpted and undercut. Instead of a gradual ramp connecting the beach to the crest of the dune, a sharp, scarred face remains. Photos by Derek Heathfield
Using the Hakai weather sensors on Calvert Island, Heathfield watched as storms battered the BC Central Coast from October to March. Over this period, approximately six Olympic-sized swimming pools worth of sand, some 15,000 cubic meters (or 23,000 metric tons), washed away. The beach height dropped by a whopping meter and a half. The loss of sand is striking, but not surprising to a geomorphologist such as Heathfield.
“Dunes are designed to handle a huge storm surge and the winter season, and then slowly rebuild themselves over the summer,” he says.
During the winter, tidal surge and storm waves compound to remove sand from the beach. Low-pressure weather systems hang offshore, driving winds and raising water level. As a rule of thumb, for every millibar drop in atmospheric pressure, sea level rises by one centimeter. During a particularly violent storm last March, the pressure drop raised sea levels by half a meter. High winds can also build up water levels and waves. If a low-pressure storm hits land at high tide, it’s adieu dunes.
“It’s not just wind and water that breaks down the dunes. The water comes in and floats huge driftwood logs. Given powerful storm waves, the logs are hurdled like battering rams against the dune,” says Heathfield.
The time-lapse cameras are effective visual tools, but to put a number on how much beach was lost over the winter, Heathfield and his team used a variety of other technologies. Using laser scanners on the ground and drones in the sky, the Coastal Sand Ecosystems team created three-dimensional maps of the beach. From there, they compared how the beach dynamically eroded and was rebuilt over the four seasons.
A three-dimensional point cloud representation of the West Beach sand dune system rendered from thousands of photos taken from a drone. This model allows scientists to calculate how much sand eroded from the beach over the winter, and how much is built back up over the summer. Photos by Derek Heathfield
“In areas of the world with coastal developments, dune erosion is a big concern,” says Heathfield, adding that there is still a lot we don’t know about the few places in BC that have sandy ecosystems. “By taking detailed measurements of how West Beach changes throughout the year, we hope to better understand how extreme storm events affect a beach and its dune system. How do extreme storm events affect the dunes? These studies help us when planning in coastal areas that are more built up.”
If you only come to the beach in July, the area may look like a tranquil spot to build an oceanfront home. But if you set up a camera for a year, you may want to reconsider. Dunes don’t sit still.