Review article: Mountain flash floods: from hazard formation to disaster risk reduction pathways

Abstract

Mountain flash floods pose growing risks under climate and environmental change, yet cross-regional understanding of their triggering mechanisms, cascading impacts and governance remains fragmented. This review synthesises 1967 studies published during 2000–2025 using bibliometric and topic analyses with qualitative synthesis. By integrating these approaches, we reveal pronounced geographical and thematic imbalances, with research concentrated in Europe and Asia. Flash-flood initiation and impacts are strongly state-dependent, emerging from interactions among storm intensity, duration and spatial concentration, antecedent hydrological conditions, surface controls, and hillslope–channel connectivity. These interactions limit the transferability of fixed rainfall thresholds and support dynamic, multi-source early-warning approaches. The review further shows how hazards are transformed into disaster risk through exposure, vulnerability and capacity conditions, leading to realised economic, social and ecological impacts and cascading disasters. Evidence across non-structural, structural and Nature-Based measures indicates that effective risk reduction requires coordinated portfolios rather than isolated interventions. We develop an adaptive governance framework integrating prevention of new risk, reduction of existing risk and management of residual risk, while addressing exceedance uncertainty, warning-to-action effectiveness, and long-term costs and trade-offs. Overall, this synthesis provides a cross-regional basis for more effective mountain flash-flood risk reduction across mountain regions facing uneven evidence and response capacities worldwide.