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TitleGlacier outburst flood on the Noeick River: the draining of Ape Lake, British Columbia
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LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorJones, D P; Ricker, K E; Desloges, J R; Maxwell, M
SourceGeological Survey of Canada, Open File 1139, 1984, 81 pages, https://doi.org/10.4095/120215 (Open Access)
Image
Year1984
Documentopen file
Lang.English
MapsPublication contains 2 maps
Map Info.surficial geology, surficial geological, 1:50,000
Map Info.surficial geology, surficial geological, 1:7,500
Mediapaper; on-line; digital
File formatpdf; JPEG2000
ProvinceBritish Columbia
NTS93D/01; 93D/02
AreaApe Lake Area; Noeick River Area
Lat/Long WENS-127.0000 -126.0000 52.2500 52.0000
Subjectssurficial geology/geomorphology; glaciers; glacial lakes; glaciation; floods
Illustrationsphotographs; geological sketch maps
Released1985 04 01; 2008 04 11
AbstractApe Lake (surface area 2.47 km2,- volume 85.5 x 106 m3, average depth 3 1.7 m) is located on the eastern side of the Coast Mountains about 3 90 km northwest of Vancouver, British Columbia. Ape Lake lies at the head of the Noeick River which drains into South Bentinck Arm and the Pacific 0cean. The lake was formed by the Late Neoglacial advance of Fyles Glacier across the Noeick valley, thereby blocking its drainage and forming a lake which spilled over a divide (1395 m a.s.l.) into the Talchako-Bella Coola river system. Since about 1900, Fyles Glacier has receded between 7.1 and 50.2 m/year while the thickness of ice in the glacier snout has decreased between 1.0 and 3.8 m/year. Between 1964 and 1978, when surrounding glaciers were advancing, Fyles Glacier receded at about 15 m/year while ice thickness decreased 2.2 to 3.8 m/year along the lake margin. With the continued recession and ablation of Fyles Glacier, the maximum thickness of ice impounding Ape Lake decreased until it was roughly 10-20 percent greater than the maximum depth of water near the ice margin. This condition appears to have been reached in late 1984 when the hydrostatic pressure of water in the lake was sufficient to lift the ice allowing water to seep beneath Fyles Glacier. About 0ctober 19, 1984, subglacial leakage from Ape Lake began to increase rapidly, melting a tunnel beneath Fyles Glacier. As the tunnel enlarged through melting, increasing volumes of water drained from Ape Lake on 0ctober 20, creating a large flood on the Noeick River downstream to tidewater. When lake levels had declined about 10 m, a climax end-moraine was exposed which divided the remaining water into two basins. The west basin continued to drain with peak discharges at the tunnel exit occurring about 1100-1200 hours on October 20. Several hours later the climax end-moraine impounding water in the east basin failed, generating a second flood which peaked at the tunnel exit around 1 63 0-173 0 hours. In total, approximately 45.8 xl06 m3, or 54 % of the total lake volume drained beneath Fyles Glacier with maximum peak discharges at the tunnel exit estimated to be between 985 and 1500 m3/s. Downstream of Fyles Glacier, the flood destroyed several km of logging road, severely damaged two bridges, razed over 200,000 recently planted trees and probably destroyed a large proportion of the salmon eggs deposited in the river gravel earlier in the year. The tunnel beneath Fyles Glacier is expected to close within 100-200 days. Once the tunnel is resealed, possibly as early as May, 1985, the lake will refill. The lake could be at or near maximum water level in late August or early September, 1985 after which it could drain at anytime. The lake is expected to drain subglacially, refilling and draining every 1-2 years. Major floods will continue until the thickness of ice damming the valley is 20-30 m lower than ice thickness in 1984. Thus, depending upon the rate of recession and ablation of Fyles Glacier and climatic conditions, major floods can be expected for at least 8 years, probably 14 years and possibly as long as 100 years. Management options to eliminate or reduce the size of future outburst floods are limited to either excavating a trench in bedrock at the east end of the lake to reduce lake levels or increasing glacier ablation rates through application of cinder or coal dust. It is recommended that no trees be replanted in those areas which are less than 5 m above the river channel and no salmonid enhancement projects should be undertaken until the potential for major outburst floods is reduced.
GEOSCAN ID120215

 
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