The 1994 jökulhlaup at Farrow Creek, British Columbia, Canada

Abstract

An ice-dammed lake at the margin of Goddard Glacier, in the southern Coast Mountains of British Columbia, drained suddenly in July 1994, producing a jökulhlaup that travelled 11 km down Farrow Creek to Chilko Lake. The jökulhlaup transported and deposited large quantities of sediment, destroyed tracts of forest, and severely modified the channel of Farrow Creek. The flood had a peak discharge of between 100 and 300 m 3 s −1 and, judging from its geomorphic effects, was much larger than normal rainfall- and snowmelt-generated floods in the basin. The lake drained via a subglacial tunnel at the base of Goddard Glacier following a lengthy period of glacier downwasting and retreat. Drainage occurred when a passageway developed at the base of the weakened dam. The escaping waters rapidly enlarged this passageway, producing a large tunnel which has not resealed since the jökulhlaup. Goddard Lake is similar to other short-lived glacier-dammed lakes in western Canada that have developed near the toes of glaciers since the end of the Little Ice Age and have disappeared after one or a few outbursts. It contrasts with other glacier-dammed lakes, commonly located farther from glacier termini, that have lengthy, stable, pre-jökulhlaup phases and long periods of cyclic or sporadic jökulhlaup activity.