Observations of Slushflows and their Geomorphological Effects in the Swedish Mountain Area

Abstract

In the Swedish mountains, the rapid mass movement of water-saturated snow, constituting slushflow or slush avalanche, occurs primarily along small streams at the time of break-up and spring warming. This process is an important geomorphic agent as well as a considerable hazard during the snowmelt season. Unlike snow avalanches, slushflows are of importance also in areas with gentle relief. Field criteria indicating slushflow hazard are bluish colour and tension cracks in the snowcover at potential starting zones.Terrain locations subject to slushflow activity can often be identified by evaluation of geomorphological features, e.g. veneers of rock debris, various erosion marks or medium-scale landforms such as slushflow fans or boulder tongues. Related processes that need to be clearly distinguished from slushflows are channel-confined wet-snow avalanches, debris flows, flash floods and river break-ups. The corresponding sedimentary deposits can be similar and correct identification may demand careful field evaluation of the mode of sedimentation or of the source area and track of the process involved.