ABSTRACT: Estimates of the magnitude of glacier outburst floods from Lake Donjek, Yukon Territory, Canada

CGRG Bibliography of Canadian Geomorphology
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Abstract

A close examination of the probable magnitude of outburst floods which may be expected from Lake Donjek in the next 50 years has been made. Few tools exist for determining the flood potential of glacier-dammed lakes. This study began by selecting an outburst flood from a reservoir of comparable size to Lake Donjek and using this flood as a reference against which to compare predictions for Lake Donjek. In the simulation model constructed, water volume was one of several factors which influenced flood magnitude. The flood data employed resulted from the event in September 1967 when Summit Lake emptied. This lake is dammed by Salmon Glacier and empties through a 12 kilometer ice tunnel into the Salmon River. A transition occurred from stable surface drainage to unstable subglacial drainage. The December 1961 outburst flood from Summit Lake damaged the Ninemile bridge across Salmon River and an access road. There are 15 recorded outburst floods from Summit Lake. The simulation model constructed was able to reproduce the essential features of the discharge hydrogen for the September 1967 outburst from Summit Lake. The volume of Lake Donjek reservoir is currently roughly 234,000,000 cubic meters, depending on the point to which the ice margin moves during a glacier advance. The empirical Clague-Mathews formula predicts a peak discharge of 2900 cubic meters per second for Lake Donjek floods. The simulation model predicts that outburst floods from Lake Donjek are likely to be more severe than those from Summit Lake. A maximum discharge in the range of 677 to 5968 cubic meters per second is predicted. The most probable range is 3968-5938 cubic meters/second

Bibliography of Canadian Geomorphology