The Great Lemieux Landslide consumed fields, trees, a road and the confidence of many residents.
By Dane Lanken
STEVE WASHAM was so intent on finding a good spot to fish one afternoon in June 1993 that he didn't realize his world was in perilous motion. The 40-year old cabinetmaker from Bourget, Ont. was driving along the South Nation River southeast of Ottawa looking for a place to put in a line, but it had rained a lot lately, the water was high, and he couldn't get close to the bank. So he hopped back into his pickup truck and drove down river to try another location. The prospects weren't any better. He did catch a curious sight, though: it looked as if there were trees moving in the middle of the river. Must be a strong wind, he thought, and headed for home.
Driving back the way he had just come on County Road 16, doing about 80 kilometres an hour, he came to what looked like a small hill. "You know when you can see the crest but not what's on the other side," he said later. He got a little closer and realized there was no other side. Where there had been pavement five minutes before there was now thin air.
Washam hit the brakes, but it was too late. He and his pickup truck sailed off the end of the pavement like a stunt car in an action movie, and landed with a thud in the middle of the Great Lemieux Landslide.
TWELVE THOUSAND YEARS AGO, when the last great glaciers melted, the land in what is now the St. Lawrence and Ottawa valleys was so depressed by the weight of the ice that salt water flowed in from the Atlantic and created the Champlain Sea. The sea lasted a couple of thousand years, salty at first, and cold from glacial meltwater; warmer and fresh as years went by. Eventually the earth rebounded, the sea drained and the rivers found their present beds. Topsoil formed on land once underwater, providing fertile ground for meadows and trees.
But underlying much of that land, in what is now eastern Ontario and western Quebec, are vast deposits of Leda clay, finely ground "rock flour" that was scoured off the Canadian Shield, mixed into glacial ice, carried away in meltwater and finally deposited as sediment on the floor of the Champlain Sea. In some places today this clay is 100 metres thick -- roughly the depth of a 32-storey building.
It is deceptive stuff: solid under most circumstances but, if given a chance, liable to liquify and flow like wet concrete. High river banks where a stream has sliced through the top layers of soil and sand, exposing the clay, afford an opportunity. The cut gives the clay a place to flow.
ALONG AN 18-kilometre stretch of the South Nation River between Casselman and Lemieux, where cliff-like banks loom 25 metres above the water, there have been landslides for thousands of years. To almost anyone driving through the area, things look perfectly normal -- the broad and peaceful river, the maple forests, the tidy farm fields -- no obvious signs that the land here could give way without warning. But along the river, there is a low, bumpy area at odds with the otherwise high, flat terrain. It looks as if the land has been scooped out and countless little piles of dirt have been dumped randomly in the depression.
"That's a slide scar," explains Dennis O'Grady, general manager of the South Nation River Conservation Authority, which is charged with improving land and water quality in the 3,900 square kilometres drained by the South Nation. Landslides have been giving the authority a headache for years.
"That one's from the 1895 slide," O'Grady says, pointing to another rough patch of land now partially covered with poplars, alders and scrubby growth. There are also scars from major slides in 1850, 1910, 1971 and, of course, 1993, plus many minor ones.
"It was the 1971 slide that got everything rolling, it was a big one," he says. "Twenty-eight hectares of land just rolled into the river. By luck no one was living there. After that, scientists looked pretty well across Canada for the combination of landslide potential and human activity ...but it seems these rock flours have to be laid down in salt water to be hazardous. Finally things got narrowed down to this section of the South Nation River."
Geologists found other slide-prone areas along the coast of Hudson Bay, but human activity is sparse there. And there are other areas once covered by the Champlain Sea which made themselves known with tragic results. One was the community of Notre-Dame-de-la-Salette, Que., on the Riviere du Lievre northeast of Hull, where in 1908 a landslide on the opposite bank sent a wave of water and huge blocks of ice crashing into the town, destroying 12 houses and taking 33 lives. Another was Saint-Jean-Vianney, Que., across the Saguenay River from Jonquiere, where in 1971 a sudden, 27-hectare crater swallowed 36 homes and killed 31 people.
So studies and more studies were done on the South Nation, and eventually two areas of particular concern were identified. One was the Casselman suburb of Seguinbourg, a cluster of about 50 homes built on the high bluffs overlooking the river. The other was the community of Lemieux, where about two dozen homes, several farms and the Saint-Joseph-de-Lemieux Church, built in 1891, stood just uphill from the riverbank.
The fear was the same in both cases: that river erosion would expose the unstable clay at the foot of the bank, causing slope failure. This process would then advance inland with ever more land loss, until (as in the earlier major slides) the whole substratum of clay would liquify and carry away huge areas of land.
One study done by Kay Klassen for the Ontario Ministry of Natural Resources in 1986 found, chillingly, "little or no difference in the properties of the ground material at Lemieux and the area of the 1971 slide."
Remarkably, however, there was still pressure from developers and some area politicians to allow new construction along the river. So in the mid-1980s, the South Nation River Conservation Authority hired Randy Morey, a Kemptville, Ont., engineer specializing in "geotechnical and hydrogeological investigations," to do a final assessment.
"We drilled dozens of bore holes along the riverbanks," says Morey, who works at home in a small office lined with books like Folding and Fracturing of Rocks and Principles of Pavement Design. "We'd go down 25 or 30 metres, take out tube samples for analysis and do shear vane testing." (That's when you put a flanged pipe down the bore hole and twist it. The torque it takes to turn it tells you the clays strength, one factor used to determine soil stability.)
"A professor I studied with at Queens University, Dr. Robert Mitchell, investigated the 1971 slide," says Morey. "He worked out formulas using weight of soil, height of bank, strength of material and other criteria to determine a site's potential for slides, and how far it's likely to retrogress from the river."
Based on these investigations, and Mitchell's theories, they identified a potential retrogressive landslide area extending 300 to 1,000 metres from the banks. This area, they later found, correlated very nicely with the old slide scars along the river.
The studies confirmed that Lemieux and Seguinbourg were at risk. At the latter, the conservation authority spent $750,000 (of mostly provincial money) constructing a berm at the base of the bank. The 1,400-metre strip of jagged quarry rock, some 30 metres wide at the bottom, was intended to solidify the bank and prevent initial slope failure.
The same offer was made at Lemieux. But since scientists couldn't guarantee that a berm would ensure 100-percent safety, the residents voted overwhelmingly to move. In 1989 and 1990, the conservation authority bought 28 houses in and around the village and helped relocate them to new sites, mostly nearby. Most residents needed little convincing to move. One or two clung briefly to it-can't-happen-here optimism, but eventually heeded the warnings as well. Still, there were many tears at leaving ancestral homesteads.
"It was social upheaval," says Gary Brad, whose family farmed just north of town for 130 years, and whose farm fields disappeared in the 1993 slide. "Especially when they took the church down [in 1992]. You know, my dad hauled stone for that church with his dad in the winter of 1917. We went there, we'd see the neighbours once a week. Now weeks go by, we don't see them."
Growing up in Lemieux, there was no fear of landslides, says Bradley "No talk or concern at all," he says. "There were slides, but they were upriver, not where we were. We didn't hear a thing until the mid-1980s." Given that the 1993 slide came within about 500 metres of Lemieux's main street, Bradley wonders if something shouldn't have been done earlier.
"It's a weird feeling," he says, "going there now, looking at the hole where our fields used to be. I don't know how many times I walked along that riverbank, bringing the cows home."
Houses along the river are still being shifted out of high-risk zones. Simonne Leroux's farmhouse, built by her husband's family in 1868, was moved away from the riverbank in August 1994. "She couldn't sleep there anymore," says her son Jean-Paul. "She was too nervous...in the last few years, everybody was scared."
The underlying cause of the 1993 Lemieux slide was natural erosion likely coupled with a high water table. It had rained a lot, and most slides occur in late spring and fall when the water table is high. But exactly why the slide occurred in that particular location at that particular time is a mystery. There was nothing obvious -- nothing like the earthquake near Quebec City in 1663 that triggered landslides all over the St. Lawrence and Saguenay valleys. Steve Washam, who was as close as anyone to the slide, heard nothing and felt nothing.
The ground just gave way, starting at the bank, moving inland, creating a crater up to 320 metres wide, 680 metres in length, and 10 to 20 metres deep. A land area equal to about 14 average city blocks -- some 3.5 million cubic metres of clay, sand, topsoil and trees -- slid into the opposite bank, then coursed both upriver and down for more than 1.5 kilometres in each direction. Debris jammed the riverbed and valley to a depth of 12 metres. It was four days before the choked South Nation flowed again, more than a year before it returned to normal levels.
Great chunks of grassland and forest remained intact and sailed like rafts over the debris. The wall of mud and water surged upriver and down, sending people who had been fishing on a bridge running for their lives. But the bridge held despite the onslaught of flying trees.
The police arrived, cordoned off the area and evacuated homes well beyond the setbacks. The curious arrived, too, the advance troops of a summer-long army of onlookers. O'Grady from the conservation authority called Morey the engineer. "There's been a slide at Lemieux," he told him. How far back, Morey asked. Seven hundred metres, O'Grady told him. Morey felt vindicated. He had set the safe limit there at 800 metres.
WASHAM FIGURES he was unconscious by the time his pickup truck hit the crater floor. The last thing he remembers was crossing his arms in front of his face. When he woke up, he was hanging upside down in his truck seat, dripping blood. The truck was on it's roof, his woodworking tools strewn about.
He broke both arms against the steering wheel, cracked two ribs, and smashed his kneecap on the gear shift. The windshield buckled in and shattered, cutting his head and face. He squirmed out of the truck and sat dazed on the mud until two area men, Denis Robert and Richard Groulx, climbed into the hole, wiped the blood off him and swatted mosquitoes while they waited for help. Before climbing into the crater, Robert and Croulx tied a chain to a tree to enable them to climb back out, but the sides of the crater were still tumbling then and the tree and the chain just fell into the hole. Two hours later an Armed Forces helicopter arrived and winched them all out. "It was like Rambo," says Washam, "guys in orange slickers sliding down a rope. We were happy to see them."
Washam spent five days in hospital and two months in casts. His auto insurance paid promptly; his property insurer said his tools weren't covered but sent a $65 cheque for his fishing tackle and notice of a premium increase. It was a month before his truck was towed out of the hole, and when it was, Washam's tools, car stereo, ignition system, license plates and transmission had been stolen.
"I got some money from the township," says Washam, who is married and the father of four. "But the accident cost me $7,000."
Today there are large signs around Lemieux that say "Danger, unstable area, no trespassing." But the curious walk past them to see the big hole. The crater floor is still ridged and bumpy, like the scars of earlier slides. There are pieces of broken pavement down there, too, and fence posts, and hydro poles with bits of wire still attached. But grass is growing there now, and young trees joining the old maples that, remarkably, survived the landslide upright.
The mood is forlorn on what was once Lemieux's main street. There are still a few driveways, but no houses, still a couple of street lamps illuminating uncut lawns. The big spruce trees beside where the church once stood are still there. The cemetery, well-kept and tidy, is off by itself at the edge of the woods.
From the bridge just down the hill, the river looks broad and peaceful. The clay is biding its time.
