ABSTRACT: Studies of some rivers and associated permafrost in northern British Columbia and Yukon.

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

This study involves aspects of flow and thaw regimes of rivers associated with permafrost in northern British Columbia, through the Yukon to the Arctic coast. Results and interpretationWithin the sporadic permafrost zone of northern British Columbia, Smith (1975) measured a lag time of two days between the centroids of spring storm rainfall and resulting stream runoff. Northwards as permafrost becomes more extensive, the lag time became increasingly shorter, presumably as runoff is progressively confined to a shallowing active layer. Although the basin areas vary in character, hydrographs for the Dezadeash River in southern Yukon, the Yukon River at Dawson in central Yukon and the Porcupine River in northern Yukon (Historical Stream flow Summary, 1980) show peak runoff becoming more intense northwards as it is confined to a shorter spring. The hydrograph for the most northerly Porcupine River shows a secondary peak runoff in late summer. McDonald and Lewis (1973) have described similar late secondary peak runoffs for rivers on the Yukon coast plain. Northern river flow is least, sometimes ceasing during winter when the river is frozen down to its bed. Some water can be injected from underground, free-flowing conduits that exist locally in the north. Underground water can be identified because it is poorer in oxygen and iron, and richerin salt compared with surface water (Scheier, 1978). Being warmer, this water will thaw river ice, locally overflowing between ice jams onto surrounding land as aufeis.Rare catastrophic events will be superimposed upon these general trends. A Gumbel (1954) Analysis plot was made for the Dezadeash River, southern Yukon, using data from Historical Stream flow Summary (1980). The 1982 flood on the Dezadeash River was so great that only a gross estimate of the volume flowing could be made. The flood caused great damage to roads and bridges near Haines Junction. Air off the Pacific looses its moisture on the windward side, and warms on the lee side adiabatically as it crosses the Saint Elias Range in the Kluane National Park, thawing snowfields.In 1982 this process was sufficiently excessive to create a catastrophic event. Migration of a meander across the Indian River floodplain, central Yukon, has conducted summer warmth into the ground, thawing the permafrost (Crampton, 1987). Permafrost became re-established after about 100 years. Migration of a meander across the Eagle River floodplain,northern Yukon, has produced thawing and re-establishment of permafrost to create artesian pressure in the talik between the thawing and freezing interfaces (Crampton, 1979). Artesianpressure can also develop between such interfaces associated with pingos (Mackay, 1973). Much more complex thawing and re-freezing states have been found under the constantly shifting bars and channels within braided river sections such as those of the lower Babbage and PeelRivers in northern Yukon. The lag time between centroids of heavy rainfall and subsequent river runoff decreases fromnorthern British Columbia, through Yukon to the Arctic coast as permafrost increasingly concentrates runoff onto the land surface. A secondary peak runoff occurs in late summer on theArctic coastal plain. Minimal river flow during winter can be augmented by injection of water from free-flowing conduits. Rare catastrophic flows are superimposed upon these flow regimes. Permafrost thawed by migration of a river meander across an area is replaced by new permafrost in the wake of meander migration. Artesian pressure can develop between thawing and freezing interfaces. Complex systems of freezing and thawing develop under braided rivers.

Bibliography of Canadian Geomorphology