Imaging water transport across the soil-snow interface using neutron transmission radiography

The soil-snow interface plays a critical role in the release of glide-snow avalanches, which threaten life and infrastructure such as houses, roads, and chair lift masts in alpine areas. One of the important factors controlling glide-snow avalanche release is the presence of interfacial water between the ground and snowpack. Several mechanisms, such as percolation of water from the snow surface and geothermal melting of basal snow layers, have been postulated to explain the formation of this interfacial water. These mechanisms remain, however, poorly understood to poor predictability of glide-snow avalanche release. Here, we demonstrate the use of neutron transmission radiography for investigating the transport of water across the soil-snow interface at laboratory scales. We show that neutron transmission radiography is capable of capturing changes in water content during snow melt processes in both the snow and soil phases. Neutron imaging also revealed that the hydraulic properties of the porous interface between the soil and snow (mimicking a vegetation layer) affect the formation of an interfacial water layer. Improved understanding of the water transport across the soil-snow interface should lead to better prediction of glide-snow avalanche releases in the future.