Sediment shape as a proxy for fluvial processes: A factorial analysis in the Yarlung Tsangpo Grand Canyon

ABSTRACT Sediment shape preserves information on sediment provenance, transport history and hydraulic‐mechanical conditions in fluvial systems. However, extracting physically meaningful process signals from high‐dimensional morphometric datasets remains challenging, particularly in tectonically active mountain rivers. This study applies a high‐throughput, image‐based morphometric framework to quantify sediment shape variability in the Yarlung Tsangpo Grand Canyon. More than 36 000 particles were analysed across multiple grain‐size classes, and 11 morphometric parameters were extracted from high‐resolution binary images. Multivariate statistical analysis (principal component and factor analysis) was used to reduce parameter redundancy and identify independent morphological dimensions. Three orthogonal morphological factors were resolved, representing outline integrity, particle elongation and edge refinement. Grain‐size trends show that coarser particles generally exhibit reduced outline completeness but increased edge smoothness, consistent with asymmetric abrasion and prolonged in‐channel residence. In contrast, elongation displays stronger spatial variability and appears broadly consistent with lithological inheritance and local sediment inputs. Along the longitudinal profile, the first two factors remain relatively stable, whereas the smoothness‐related factor varies markedly near tributary confluences and downstream geomorphic transitions, highlighting the influence of hydraulic reworking and local sediment mixing. Incorporating particle elongation into sediment transport threshold calculations reduces predicted sediment flux relative to conventional spherical assumptions, indicating that particle shape may influence transport estimates in steep mountain rivers. By linking dimensionality‐reduced morphometric structure to geomorphic context, this study demonstrates how sediment shape metrics can provide process‐relevant insights into sediment dynamics and offers a quantitative framework for integrating particle morphology into sediment transport analyses in tectonically active river systems.