Sea to Sky: Living with mountains, earthquakes, landslides and floods
Sea-to-Sky country is a remarkable mountain landscape. Much of the dramatic beauty is created by our narrow valleys and steep mountain slopes. As such, we are mountain people. But unlike other mountain people, such as the Swiss or Japanese, we have recorded our life among our mountains for only a short while. Our experience with the Coast Mountains, extends back less than 150 years to the era of first European settlement. The stories of the First Nation peoples extend back further, and generally tell of the rare spectacular events. Most of us have lived here for less than a decade or two. As such, we are still learning how our mountains behave. We are still learning nature’s "rules" – and these include floods, landslides, debris torrents, earthquakes, and even volcanic eruptions.
Fortunately, those natural hazards that are frequent also tend to be small, the larger events are much less frequent, and giant events are rare. We have lived here long enough to experience 10-year, 50-year, and even 200-year floods, but perhaps not 500-year floods. We have experienced small rock falls, and remember the ones that closed the highway for a day or a week. But we have not experienced giant landslides, the size of Hope Slide east of Hope, even though the valleys of Sea-to-Sky contain giant landslide deposits. Highway 99 crosses two giant landslides between Whistler and Pemberton, and another near Daisy Lake Dam.
We know a giant earthquake rocked our region on Jan. 26, 1700, and other major earthquakes occurred in 1872 and 1946. Future major earthquakes are just a question of when, not if.
Even a Sea-to-Sky volcanic eruption cannot be ruled out. Nearby Mount Meager erupted about 2,400 years ago in an eruption somewhat similar to the 1981 Mt. St. Helens eruption.
In spite of our short tenure in Sea-to-Sky country, with nature as our teacher, we have learned a considerable amount. We would be wise to remember the lessons, as most of the instruction involved tragedy. An early lesson learned was "If the land is flat, it might flood". Early settlers to the Squamish area were drawn to extensive flat lands near the mouth of the Squamish River, a rare commodity in Sea-to-Sky country, but they quickly came to realize that it came with a price. Downtown Squamish was flooded numerous times in the first half of the century, with major floods in 1921 and 1940. Modern dykes reduce the risk of a repeat, but they do not eliminate it. Parts of the Squamish dyke barely held during the flood of October 2003.
Another lesson, learned early, was that steep slopes can fail. The young Britannia mine learned this through terrible tragedy. Fifty seven miners were killed when a landslide roared through their bunkhouses high on Britannia mountain on a winter night in 1915. This remains the largest loss of life by natural disaster in British Columbia’s recorded history.
Recent history contains more lessons. When Highway 99 was built in the 1950s, the engineers designed the bridges along the highway to withstand anticipated floods. The engineering community did not know that debris torrents, waves of mud, stone, and tree debris, could race down steep Coast Mountain stream channels. We learned this when a debris torrent destroyed the M Creek bridge north of Lions Bay during a severe rainstorm in 1981, and seven people died as cars drove into the void. Today, bridges are designed to withstand such debris torrents.
And so it goes. We will continue to learn from nature. The important lesson is that we remember the experiences, and learn from them, so that we reduce our future risks. We live in a geologically active area – we need to plan accordingly.
Whistler Naturalists Speaker Series – Sea-to-Sky Country: Living with mountains, earthquakes, landslides and floods with Bob Turner. Dr. Bob Turner is a scientist with the Natural Resources Canada (Geological Survey of Canada) in Vancouver. His recently released book with co-author John Clague, Vancouver, City on the Edge — Living with a Dynamic Geological Landscape, presents the science behind important geoscience issues in southwestern British Columbia such as earthquakes, landslides, floods and volcanoes, as well as groundwater and surface water resources, energy and mineral resources, and the impacts of climate change. Event will take place Wednesday, March 17th at 7:30 p.m. at MY Place (doors open at 7 p.m.). Admission by donation, children free.
Monthly Bird Walk — The next bird walk will take place Saturday, April 3rd. Join Whistler experts in the monthly update of our feathered locals and migrants. For details, contact Michael Thompson.
Written by: Dr. Bob Turner