HISTORICAL NEWS SEARCH - Government of British Columbia

According to the report, it is probable that any slide would be limited to a “single, intact unit containing
about 50 million yd. 3 (38.2 million m 3 ) of rock. “It can be seen that a slide of 50 million yd. 3 (38,230,000 m 3 ) from
the central section of the slide would not fully obstruct the reservoir. There are a number of factors that indicate that
the landslide has a long history of movement. Soil slumps have occurred along the shoreline during the last few years
where the terraces have been undercut by wave action.”
The report noted cracks in sandstone rocks, which in two cases “had toppled trees, which were still green at
the time of observation.” It concluded that the slide is very ancient and recent measurements reveal “that a slow
apparent downhill movement is taking place.” The report recommended that the survey program be expanded to cover
more of the slide. This recommendation was accepted giving the slide 11 instead of five markers. Since 1973, the
original markers on the slide had shown much smaller movement.
A second report dated May 1975 and based on 1974 survey work, states that the slide movement has slowed
down since the reservoir filled. But the report quotes Victor Dolmage as suggesting that monitoring of the slide
“should continue, since the problem of land and rockslides occurring on the shorelines of large reservoirs is becoming
more and more important.”
On December 15, BC Hydro released a press statement from an October, 1974 report by its consulting
geologist, Dolmage. Having reviewed the results of geological mapping, Dolmage concluded there was “high
improbability of a recurrence of a landslide at this locality and virtually no chance of its causing any damage to the
Bennett hydro-electric station.” He continued, ”Since the main mass of slide debris has moved (in geological times)
down a steep to a flatter slop, much of the propelling force has been dissipated and the chances of repeated sliding
reduced accordingly. A slide, no matter how large, moving slowly down such a gentle slope into the deep, wide
Williston Lake is not likely to generate a wave large enough to reach, let alone damage, the Bennett complex.”
BC Hydro stated in its press release that the slide was first mapped in 1950 and was studied by Hydro
consultants before the filling of the Williston reservoir in 1967. BC Hydro later said that the massive 5.5-mi. 2 (14.25
km 2 ) slide, virtually a mountainside, did not pose danger to people living below the dam.
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*1) The Downie slide, the toe of which would be in the reservoir of a new dam approved for construction above
Revelstoke, contains an estimated 1 billion yd. 3 (0.76 billion m 3 ), about 60 times the 1965 Hope slide (The Vancouver
Sun, December 4, 1976).
*2) Extensive studies were done on three large slides that fringe the reservoir on the Mica Dam on the Columbia River.
The Downie slide was the major concern in considering the new dam to be built between the Mica Dam-Revelstoke
(The Vancouver Sun, December 4, 1976).
January 16-18, 1977
Event type: Rockslide and flooding.
Precipitation: Hartley Bay (104.6 mm/1 day), January 16, 1977; Sewell Inlet (106.9 mm/1 day), January 16, 1977;
Kildala (86.4 mm/1 day), January 16, 1977; Tasu Sound (73.7 mm/1 day), January 16, 1977; Salvus Camp (70.6 mm/1
day), January 16, 1977; Ocean Falls (105.4 mm/1 day), January 16, 1977; Stewart A (107.7 mm/1 day), January 16,
1977; Kemano (114.0 mm/2 days), January 16-17, 1977; Terrace (76.0 mm/2 days), January 16-17, 1977; Bella Coola
(98.0 mm/2 days), January 16-17, 1977; Kitimat Townsite (107.2 mm/2 days), January 16-17, 1977; Falls River (179.4
mm/3 days), January 16-18, 1977.
Source: The Herald, January 19, 1977; The Daily News, January 17, 1977; The Informer, January 22, 1977.
On January 16, a rockslide blocked Highway 16, 20 mi. (32 km) east of Prince Rupert. One large boulder had
to be blasted off the highway, which was expected to be cleared on January 17.
In Terrace, minor flood damage was reported. In Ocean Falls, the Shanghai Inn was flooded. The whole
place was under several inches of water. It was caused by a plugged drain near the back entrance.
October 21-24, 1977
Event type: Debris slides and flooding.
Precipitation: Hartley Bay (121.7 mm/1 day), October 21, 1977; Sewell Inlet (106.4 mm/1 day), October 21, 1977;
Falls River (128.0 mm/2 day), October 21-22, 1977; Terrace (77.7 mm/2 days), October 21-22, 1977; Kitimat
Townsite (102.9 mm/2 days), October 21-22, 1977; Kemano (209.5 mm/4 days), October 21-24, 1977; Sandspit A
(92.9 mm/4 days), October 21-24, 1977; Kildala (155.0 mm/4 days), October 21-24, 1977; Bella Coola (93.4 mm/2
days), October 21-22, 1977; Ocean Falls (190.0 mm/2 days), October 22-23, 1977; Tasu Sound (88.9 mm/1 day),
October 24, 1977.
Source: The Herald, October 21 and 24, 1977; The Daily News, November 2, 1977, (October 21-24, 1977: Not
available); The Informer, October 29, 1977; Lewis and Moran 1985 (p. 5.202, Storm No. 97).
For the month of October, Digby Island reported 20 days of winds 25 mph (40.2 km/h) or higher, with gusts
reaching 55 mph (88.5 km/h) on November 22 at midnight. This windy weather was caused by three extremely deep
and intensive lows passing through the area during October (Lewis and Moran 1985). The total precipitation was
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