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Cathedral Mountain debris flows, Canada

  • L. E. JacksonJr.
  • O. Hungr
  • J. S. Gardner
  • C. Mackay
Article

Abstract

Historic debris flow activity along the north side of Cathedral Mountain in the southern Rocky Mountains of British Columbia, began in 1925 and has increased in frequency up to 1985. A typical debris flow event involves approximately 100,000 m3 of material. Debris flow velocities and discharges above the head of the fan crossed by the Trans-Canada Highway and the C.P.R. mainline are 5.5 m/sec and 210 m3/sec. Most of the large debris flow events are associated with jökulhlaups from Cathedral Glacier. Jökulhlaup discharges of at least 10,000 and perhaps as much as 24,000 m3 of water mobilize these debris flows. Part of the water may have come from a small ephemeral lake on the south side of the glacier. The balance must have been stored within the glacier. The onset and acceleration of debris flow activity was apparently induced by the recession of Cathedral Glacier. Source areas of debris flow sediments have retreated upslope since initiation of debris flow activity. C.P.R. began pumping meltwater from the glacier in 1985 and no jökulhlaups or significant debris flows have occurred since. This preventive measure should either eliminate jökulhlaups or reduce their magnitudes should they occur. Without jökulhlaups, debris flow hazard in the area should be reduced both in frequency and in magnitude.

Keywords

Debris Flow Debris Flow Deposit Debris Flow Event Debris Flow Hazard Debris Flow Activity 

Les coulées boueuses de Cathedral Mountain, Canada

Résumé

Les coulées boueuses sur le côté Nord de Cathedral Mountain, partie sud des Montagnes Rocheuses de Colombie-Britannique ont commencé à se produire en 1925 et leur fréquence a augmenté jusqu'en 1985. Une coulée typique se caractérise par un déplacement d'environ 100 000 m3 de matériaux. La vitesse et le débit des coulées au-dessus du cône d'éboulis traversé par l'autoroute trans-canadienne et par la voie ferrée sont respectivement de 5,5 m/sec et 210 m3/sec. La plupart des coulées se produisent lors de venues d'eau brutales provenant du glacier de Cathedral Mountain. Ces venues d'eau d'au moins 10 000 m3 et peut-être jusqu'à 24 000 m3 sont à l'origine des coulées. Une partie de l'eau provient probablement d'un petit lac temporaire situé sur le côté sud du glacier. Le reste est stocké dans le glacier. La fréquence plus élevée des coulées est apparemment liée au recul du glacier. Les zones de mobilisation des débris entraînés par les venues d'eau sont situées plus haut sur les pentes qu'au début de l'activité des coulées. La société gestionnaire de la voie ferrée a commencé à pomper l'eau de fonte dans le glacier en 1985 et depuis aucune venue d'eau brutale ni coulée boueuse importante ne se sont produites. Cette mesure préventive devrait ou éliminer les venues d'eau brutales ou réduire leur importance si elles se produisent. Sans ces venues d'eau, le risque de coulées boueuses devrait être réduit, aussi bien en fréquence qu'en volume.

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Copyright information

© International Association of Engineering Geology 1989

Authors and Affiliations

  • L. E. JacksonJr.
    • 1
  • O. Hungr
    • 2
  • J. S. Gardner
    • 3
  • C. Mackay
    • 4
  1. 1.Geological Survey of Canada Terrain Sciences DivisionVancouverCanada
  2. 2.Thurber Consultants LtdVancouverCanada
  3. 3.Department of GeographyUniversity of WaterlooWaterlooCanada
  4. 4.Engineering-System Windsor StationC.P. Rail LtdMontrealCanada

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