Compound Hydro-Geomorphic Hazards in European Mountain Regions: A Roadmap for Research on Postfire and Frozen Soil Dynamics

Abstract

Mountain regions in Europe increasingly face compound runoff-related hazards under a changing climate. This article compares postfire surface runoff (PFSR) and frozen-soil surface runoff (FSSR), 2 processes typically studied separately but sharing key meteorological triggers, as well as initiation and propagation mechanisms. Both are triggered by short, high-intensity rainfall acting on infiltration barriers: hydrophobic layers in burned soil and pore ice in frozen soil. Despite distinct thermal and seasonal contexts, PFSR and FSSR exhibit convergent process chains characterized by reduced interception, limited infiltration, surface ponding, and efficient sediment entrainment. Their occurrence increasingly transcends expected seasonal regimes, reflecting climate-driven shifts in fire activity, snow dynamics, and freeze–thaw cycles. Building on these parallels, this study proposes a research framework and outlines a future research agenda that links mapping, monitoring, experimentation, modeling, and governance. It advocates integrated observation networks combining remote sensing and in situ techniques, controlled experiments to quantify thermohydraulic and erosional processes and changes in vegetation cover, and physical models capturing preferential flow and transient infiltration barriers. For risk management, the article stresses predictive early warning systems that provide sufficient lead time to manage evacuations and infrastructure protection. By identifying shared mechanisms and converging research needs, this contribution supports a future research agenda and cross-disciplinary strategies for mitigating emerging compound hazards in alpine environments.