Classification of Colluvial Channels in a Mountain River: A Case Study of ‘Seoul National University Check Dam’ Catchment in Mt. Gwanak

The increasing frequency of extreme rainfall events due to climate change has heightened the risk of geomorphic hazards, such as debris flows and landslides, in mountainous areas. Colluvial channels, which typically occupy the uppermost sections of mountain river networks, serve as primary pathways for sediment transport during these events. Despite their geomorphic significance, few studies have classified colluvial channels, exhibiting diverse morphologies and processes over short distances, at the catchment scale. This study aims to classify colluvial channel subtypes in a granitic headwater catchment in Mt. Gwanak using a high-resolution (1 m) digital terrain model (DTM) generated from UAV-based LiDAR. For this purpose, 515 segments (10 m each) from colluvial channel network were extracted, and five geomorphic attributes were calculated from each segment: channel gradient, unit stream power, channel sinuosity, valley bottom width, and sediment connectivity. Hierarchical clustering based on the attributes revealed three subtypes: deposition-dominated, erosion-dominated, and highly coupled hillslope-channel reaches. ANOVA and PCA results indicated that channel gradient and valley bottom width were the most influential variables, with sediment connectivity also contributing to subtype differentiation. These findings highlight the morphological diversity of colluvial channels and offer a foundation for improving our understanding of sediment dynamics in mountainous areas.