Downslope Soil Movement at a Sub-Arctic Location With Regard to Variations with Depth

Abstract

Soil movements resulting from solifluction or similar processes have been investigated at Schefferville, P.Q., Canada, where the variation of movement with depth below the surface was specially considered.Tubes up to 2 m long were inserted vertically in the ground and their subsequent deformation (if any) measured with special probes, which passed down the tubes in situ. Some sites proved to be entirely stable despite vegetational characteristics that might have been related to disturbance. Movements at the surface of more than 10 cm/yr. were recorded on a 20° bare slope covered with small stones.Similar large movements were recorded on a lobate terrace-like feature with a general 8 to 10° slope. The distribution of movement with depth was such as to produce a typically concave downslope form in the tubes. The movements varied in intensity and from year to year; they decreased with depth, and were not measurable below about 1 m. Although they are similar to those observed by Rapp and others, they are remarkable in view of the slight slope on which they occurred. Analysis shows that consolidation following frost heave is probably not the sole cause. A stability calculation of the type commonly used for engineering purposes would have given no indication of the occurrence of movements of the magnitude observed. They might have been suspected, however, from geomorphological considerations of the origin of the surface features of the affected area.