Part of the Sentinel Glacier Basin (5 km2) in British Columbia was subject to sudden winter flooding. Meteorological and hydrological data indicate that the flooding occurred in January, at subzero temperatures when winter streamflow was assumed to be negligible. A sudden release of water deposited a layer of sediment composed of silt, sand, gravel, and rock fragments, generally well sorted, that became incorporated within the snowpack. Deposition occurred when the ground was covered with snow several metres thick. The volume of transported material is estimated at 6.6 × 103 m3; the layer averaged about 10 cm in thickness over a distance of 1 km.