Occurrence of surface flow on arctic slopes, southwestern Cornwallis Island

Surface flow on arctic slopes is due to a rise of the suprapermafrost water table above the ground surface. The active layer therefore has to be saturated, or surface flow will be lost to infiltration.In spring, snowmelt supplies abundant water to the slopes, but a shallow frost table restricts the active layer storage capacity. This produces extensive surface flow, delivering considerable volumes of water downslope as overland flow or rill runoff. As the snowpacks are reduced and ground thaw increases the subsurface storage capacity, surface flow declines in magnitude and in areal coverage. During most summers, subsurface flow dominates, except when occasional rainstorms of high intensity raise the water table above the ground to rejuvenate surface runoff.The occurrence of surface flow is controlled by slope material, slope profile, and the water balance. Spatial and temporal changes in these controlling variables always result in a highly dynamic pattern of surface flow on arctic slopes.