Hydraulics of Channelized Flow in Ice-Supersaturated Debris: 1. Rock Glacier Hydrology in Alpine Glacial-Periglacial Systems

Abstract

Frozen sediment accumulations, including rock glaciers, talus, and moraines, constitute complex aquifers in permafrost-affected terrain. The spatial distribution of permafrost ice largely governs the flow of water through the subsurface, which exhibits a spectrum of flow patterns, ranging from diffuse flow through a porous matrix to concentrated flow along discrete channels. This study characterizes the groundwater flow system within three active rock glaciers drained by springs in the Austrian Alps. We study the alteration of recharge pulses traveling through the rock glaciers to decipher the dominant flow pattern. Key hydraulic properties are explored through a combined evaluation of spring hydrographs and fluorescence tracer tests. Water predominantly flows through a network of channels within the frozen subsurface. This flow is rapid and highly turbulent, implying high energy dissipation and effective heat transfer. Although the channels exhibit large hydraulic diameters, their irregular structure contributes to exceptionally high frictional resistance. These high energy losses accelerate the melting process and promote flow-melt feedback loops, driving permafrost degradation and facilitating flow concentration. Ultimately, the hydraulic properties of these channel networks influence permafrost thaw, solute transport, lake outburst hazards, and slope stability.