North Shore to see four times as many landslides

The North Vancouver district is one of the best in landslide mitigation, says the geoscientist

Landslides on the North Shore are expected to become more violent and frequent, a new study has found – a devastating consequence of a changing climate.

“The increase in the regional frequency of landslides can be as much as 300 percent – a quadrupling of the frequency,” said lead author of the study Matthias Jakob. “It is sober, but it falls in line with many other climate changes. Predictions for most geophysical phenomena have become more serious, not less.”

The study, which was built on a Jacob did in 2009, looked at previous landslides on the North Shore and determined how much rain had fallen immediately before, which saturated the earth. Jakob then included the latest climate modeling data to predict the expected change in the amount of rain that accompanies a warming climate, and predicted the increased frequencies of landslides between now and 2080.

“Back in 2009, we had thought that climate change would have a fairly modest effect on landslides – perhaps an increase in landslide rates of 10 percent or so,” he said. “Of course, a change from 10 percent to 300 percent is pretty deep.”

In a separate analysis that looked at the extent of landslides, Jakob found that the volumes of landslides could increase by 50 percent.

“The amount is important, because the bigger the landslide, the longer it runs,” he said. “They have higher impact force, which in turn means that if and when they hit a building, it is more prone to damage or destruction.”

The results have obvious implications for human infrastructure such as roads, culverts, bridges, railway lines, paths, pipelines, power lines and other urban development, Jakob said. Everything built now should be designed to higher standards, taking into account the same climate modeling data that his studies have.

However, slipping into bodies of water also affects aquatic habitats, and slides hitting the Capilano or Seymour water reservoirs can quickly result in turbidity problems in the water supply.

Some areas on or near steep slopes may no longer be suitable for development, even though “view homes” are valued in the real estate world, Jakob said.

Jakob’s results are published in the latest issue of the academic journal Geomorphology. The study was sponsored by BGC Engineering, the Vancouver-based company that Jakob works for, and Metro Vancouver.

The results could be extrapolated to other parts of the south coast with similar geological conditions, Jakob said, but many of these areas do not actively measure landslide activity and monitor for risk, as the District of North Vancouver and Metro Vancouver do.

Deadly landslides have already happened

In 2005, North Vancouver resident Eliza Wing Mun Kuttner was killed when her home was swept down the Berkley-Riverside Escarpment in a landslide after days of heavy rain.

Thereafter, the District of North Vancouver became more proactive about the risk, and Jakob said there is no need for the average homeowner to panic.

“The district of North Vancouver has one of the best landslide management systems in Canada,” he said.

Mayor Mike Little said the fatal landslide has not been forgotten. In the four days leading up to the landslide, about 275 millimeters of rain fell. Two weekends ago, the North Shore saw 150 mm in just two days, he noted.

“This 2005 roller coaster really became a benchmark for many of us,” he said. “This is something we are monitoring very closely and we are trying to redirect more capital resources to better manage the impact. It is a very real concern for us.”

The district has installed physical infrastructure such as concrete piles and catch basins in high-risk areas, Little said.

“It’s all heavily built infrastructure to manage the potential for not just floods, but the waste stream,” he said.

Erosion is also a concern. In light of the naturally occurring outbreak of onion moths, which causes great damage to large shards of trees, the district is working on some mitigating plans, including possibly replanting areas hardest hit with more resistant species.

These measures are in line with learning to live in an increasingly hostile climate, Jakob said. But all levels of government need to think about what drives climate change and the devastating risk it entails, and also act on it, he added.

“In the bigger picture, emission reduction is the most urgent of all measures, absolutely,” he said.

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