Review: The Importance of Lateral Flow Through Snow in Hydrological Processes Globally

The flow of liquid water through snow is a complex and poorly understood problem in snow hydrology. This paper reviews current understanding of the lateral flow of water through snow. We determined that the main physical processes producing lateral flow are: (a) hydraulic barriers at layer interfaces, (b) soil saturation overland/through-snow flow, and (c) infiltration excess through-snow flow. These processes result in increased potential for lateral flow where snowpacks have more complex stratigraphy and the rate of snowmelt input is greater than the storage or infiltration capacity of the underlying soil. A global snow classification shows lateral flow through snow is important for consideration in 75% of the total global cryosphere and 50% of global seasonal snow coverage. Lateral flow is important for 70% of the cryosphere in North America and 46% of the Cryosphere in Europe and Asia. Knowledge gaps in current understanding outline future research needs which include: (a) improving hydrologic model structures to include lateral flow through snow, (b) expanded research in parameterizing the hydraulic properties of snow, and (c) further understanding of the spatial and temporal scale of lateral flow through snow processes.