Mountainous small watersheds are fundamental geomorphic units that integrate hillslope, channel, and valley-floor processes and exert first-order controls on runoff routing, sediment transfer, and landscape organization in complex terrain. Although numerous morphometric indices have been developed, most existing approaches remain dominated by single-view or two-dimensional descriptors, limiting their capacity to represent integrated three-dimensional watershed geometry and regionally coherent geomorphic organization. To address this limitation, this study proposes a three-view geometric framework that explicitly integrates planform configuration, cross-sectional valley structure, and longitudinal profile geometry. Based on geomorphometric and hydromorphological principles, a systematic parameter system is developed and applied to 13,724 mountainous small watersheds in Southwest China. Spatial autocorrelation and clustering analyses are employed to examine the statistical properties, spatial organization, and typological differentiation of watershed geometry at the regional scale. The results show that most geometric parameters exhibit significant global and local spatial autocorrelation, demonstrating that watershed geometry is spatially structured rather than randomly distributed. Distinct clustering patterns reflect coherent geomorphic controls associated with tectonic forcing, macro-relief organization, and long-term erosional adjustment. The identified geometric types represent integrated responses to valley confinement, longitudinal energy gradients, and planform organization, rather than simple variations in elevation or relief magnitude. High-relief regions may host multiple geometric configurations, whereas regions subjected to prolonged fluvial adjustment tend to converge toward more uniform watershed geometry. By explicitly incorporating three complementary geometric perspectives, the proposed framework advances conventional watershed morphometry and provides a transferable basis for regional comparison, highlighting the value of multi-view geometric representation for interpreting watershed structure, geomorphic sensitivity, and landscape organization in tectonically active mountain regions. • A multi-view geometric parameter framework is developed for mountainous small watershed assessment. • Seventeen geometric parameters quantify watershed structure from planform, cross-sectional, and longitudinal perspectives. • Spatial autocorrelation and clustering reveal regionally organised watershed geometric patterns. • The framework supports indicator-based evaluation of landscape and environmental constraints in mountain regions.
Li et al. (Fri,) studied this question.