Processes controlling the rapid drainage of two ice‐rich permafrost‐dammed lakes in NW Canada

Abstract This paper considers the processes controlling the rapid drainage of ice‐rich permafrost‐dammed lakes. It is postulated that the primary process controlling lake drainage is the melting of ice‐rich permafrost, in a manner similar to that controlling the drainage of glacier‐dammed lakes. Two lakes are considered in the analysis: one that drained naturally over a period of less than 16 h, and Lake Illisarvik, which was experimentally drained in 1978. Preliminary analysis showed that the energy contained in the lake water was sufficient for melting the ice content of the resulting drainage channel for both study lakes. Discharge estimated using a glacier‐dammed lake model developed by Clarke ( Journal of Glaciology 1982; 28 : 3) compared reasonably well with measured discharge during the period of rapid channel enlargement at Illisarvik, and resulted in the draining of Trail Valley Creek lake within the brief period indicated by a gauging station. These results suggest that melting of the ice‐rich permafrost during drainage dominates at least the early stages of drainage. However, further work is required to consider the processes of mechanical erosion, which in some cases may dominate the later stages of drainage, and to consider the appropriateness of certain assumptions in the lake drainage model. Copyright © Environment Canada 2001 Reproduced with Permission of Environment Canada.