Preferential flow paths in active rock glaciers

Abstract

Rock glaciers are key components of alpine hydrology, regulating groundwater flow and shaping catchment responses in permafrost-affected environments. While traditional models represent subsurface flow as diffuse through a porous matrix, field evidence increasingly demonstrates that channelized flow exerts a critical influence on groundwater dynamics. This review explores the hydrological processes governed by these channel networks, which enable rapid, turbulent water movement along distinct pathways. Observations of channels and hydraulically related features from 73 sites across mountain regions worldwide, viewed through a range of disciplinary perspectives, are synthesized into a unified conceptual framework. Building on this body of field evidence, we analyze the implications of channelized flow for groundwater movement, water quality, solute and heat transfer, permafrost degradation, and slope stability, advancing understanding of these interconnected processes. Our synthesis suggests that channels enhance water transport efficiency, accelerate permafrost thaw, and trigger debris flows and thermokarst lake outburst floods. The rapid transfer of suspended and dissolved matter makes downstream springs vulnerable to contamination and affects their suitability for water supply. Through integrating field observations, geophysical surveys, tracer experiments, borehole data, and ground temperatures, we reveal key processes governing water movement and its interconnected effects on heat, solutes, and permafrost structure in rock glaciers and related periglacial systems. We propose a novel conceptual model that integrates preferential flow paths into the framework of permafrost hydrology and identifies new directions for investigating hydrological processes in alpine aquifers.