Reach-based hydromorphological survey and morphometric analysis of a headwater catchment: Várvölgy Stream, Mecsek Hills (Hungary)

Small watersheds in low mountainous areas play a critical role in downstream river dynamics by serving as key sources of sediment transport. Moreover, these regions are prone to sudden and intense flash floods, particularly during extreme weather events, which have profoundly reshaped the morphology of small streams in the Mecsek Hills and surrounding rural areas over the past two decades. Despite their significance, prior research on the hydromorphological characteristics of headwater catchments in low mountainous regions of Hungary remains scarce. This study aims to investigate the essential hydrogeomorphological properties of a first-order stream catchment, with the goal of assessing flash flood vulnerability and the complex interactions among landforms within a micro-watershed. To this end, an extensive and detailed Geographic Information System (GIS) analysis was conducted at 50-meter segment intervals. Results indicate that, relative to the broader Mecsek Hills region, the study area exhibits moderate to medium susceptibility to flash floods. Field assessments further revealed that 72 out of 103 surveyed stream segments contained stable woody debris jams—important channel features that function as natural barriers, influence channel evolution, and contribute to flood hazard mitigation. These findings enhance the understanding of headwater catchment dynamics and provide a basis for improving flood risk management in similar low-mountain landscapes.