Slushflow Avalanches of the Atigun Pass Region, Central Brooks Range, Alaska
Christopher R. Smith*, Department of Geography, Indiana University
SLUSHFLOW AVALANCHES of the Atigun Pass of the central Brooks Range were again investigated during the 1979 field season. Slushflows are a unique type of wet-snow avalanche found only in arctic and sub-polar alpine areas and associated with spring break-up. The flow is described as a mud-like flowage of water-saturated snow moving along stream channels. The objective of the 1978 research was to map the locations of probable slushflow chutes and assess the natural hazard potential. The 1979 research effort concentrated on the actual break-up phenomenon and attempted to observe slushflow activity as well as to confirm data gathered in the previous season. The extra effort made to be in the area prior to breakup proved fruitful as slush and debris levees of three slushflows were observed in two chutes within 24 hours after the flows occurred. Based on observations of the snow-pack conditions prior to the flows and the physical characteristics of the chutes, two classes of flows were identified: low-gradient and high-gradient. Both flows transported large amounts of sediment. However, the high-gradient flows occurred in a more confined channel and were much more erosive than the flow observed in the low-gradient stream bed. Though the low-gradient flow occurred in a channel perpendicular to the pipeline haul road, most of the flow was channelled through the multiplate culvert pipe. This suggests that the low-gradient flows are of insufficient energy to represent any substantial hazard to the existing oil pipeline, haul road, or the proposed ALCAN gas pipeline. However, while the erosive energy of the high-gradient flow suggests potential hazard, the observed flow occurred parallel to the road and could not be considered hazardous. This project was funded in part by the American Alpine Club. A full report is on file at the A.A.C. headquarters in New York.
* Recipient of an American Alpine Club Scientific Grant.