Willows offer solution to Saanich’s erosion

Willow wattling stabilizes banks, grows immediately

George Zeman stands on the willow waddling that has stabilized the bank of his waterfront home on Juniper Avenue in Gordon Head (off Ash Road).

Water seeps out about halfway down the terraced bank of George Zeman’s property.

Zeman has no idea how much water from the Gordon Head water table is flowing out the middle of his embankment on a sunny Tuesday afternoon, but it jets out in streams when it rains, he says.

From his beachfront yard, which is high on a hill just off Ash Road near Mount Douglas, it’s about 100 feet down, a dangerous 64 degree slope to the section of beach a little south of the Mount Douglas Park’s beach.

In recent years the bank of the property was slowly collapsing, unstable and at risk, but not anymore.

Last month, a crew led by innovative soil bioengineer David Polster stabilized the bank with nearly 1.5 kilometres of linear wattling – a terrace that’s staircase like – made out of stakes and branches of native willow. The stakes are driven into the ground, and the branches laid sideways.

The bank looks foreign, like something from an ancient time. But it will soon be green, and in 20 to 30 years it will be a lot closer to what it looked like when view-seekers began removing the Douglas fir and trimming other trees from the slope.

Willow, Polster explains, is chosen for its propensity to propagate.

“The bank is stable as soon as the wattling is done, but now it will get even stronger as the willows root in,” Polster said. “You cut a willow and it suckers up into stems.”

In fact, the willow is collected as surplus from around Vancouver Island in such places as train tracks and under power lines, Polster said.

It’s one of the most creative solutions to Saanich’s erosion problem. A short walk along the beach north of Cormorant Point in Gordon Head reveals a series of recent washouts along the bank.

Polster recently installed the wattling onto another slope near Vantreight Park and onto a crumbling bank off of Noble Road in Cordova Bay. He started doing this in 1987, stabilizing and restoring the steep oceanfront slopes of the University of B.C.

The slides along Saanich’s east coast from Cormorant Point to Island View Beach will continue to happen, Polster said.

“With more intense weather events and the lack of trees on the slope it will keep happening.”

It’s not just rain causing the erosion, it’s 50 years of tree removal and pruning to maximize ocean views. It’s been a dangerous combination with the heavy runoff of water from Gordon Head. The suburban neighbourhood is lauded for its trees, but the current canopy is only a fraction of the trees that once soaked up the majority of rainfall and expelled it back into the atmosphere. That rain now falls on impervious surfaces such as roads and roofs and is collected and directed down storm drains that blast through Mount Douglas Creek. The rest of it is flushing sediment out of the banks of the cliffs overlooking the Salish Sea at an alarming rate.

As for Zeman, he doesn’t know if the previous owners were completely irresponsible in cutting the trees or just over-pruned them. Nonetheless, the trunk of a tree is only strong for a few years. Maybe the original owners of the many homes along the banks of Gordon Head didn’t realize that they culled groves of Douglas fir.

“It’s all about the view,” Zeman smiles.

It’s been just a few weeks and new growth is visible on each level of the wattling.

“Over the course of the next 10 to 15 years, alder, poplar and maple will likely move into the slope,” Zeman said. “After that, we expect Douglas fir to come back as well.”

The benefits of using willow are many. For one, it’s a native species permitted in Saanich’s strict riparian zones. Once the willows reach a height that blocks the view from the house, they can be carefully topped and will continue to grow, but with a bushier tree. The willows at the base of the slope, dozens of which are already started, will be permitted to grow quite large.

Polster even found a willow on the border of the property.

Within the wattled slope Polster also installed a series of live drains, where bundles of willow branches are laid in succession to guide the water runoff down to the beach without bringing sediment with it.

“The water has to be allowed to make it out or the bank will burst,” Zeman said. “It’s amazing how the water washes sediment down to the beach, and then the tide washes it all away.”

In some spots of his slope, mostly near the top, the crew installed rebar stakes, with a drill and an auger, where the hardpan clay was too strong for the willow.

The willow stakes are driven a metre down and protrude about 25 centimetres out of the ground.

Altogether, a crew of four worked for six weeks on the project, which cost about $100,000. It’s a steep price to pay, but it was part of the plan all along.

“When we bought the house three years ago it was at a discount because of the unstable bank,” said Zeman, a contractor nearing retirement. “I knew we could fix it. I didn’t know how, but I knew we would.”

 

reporter@saanichnews.com

 

 

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