Data of paper "Sediment Shape as a Proxy for Fluvial Processes A Factorial Analysis in the Yarlung Tsangpo Grand Canyon"

This study addresses the current lack of research linking particle shape characteristics with fluvial dynamics and sediment supply processes. Field investigations were conducted in the remote Yarlung Tsangpo Grand Canyon, spanning from the confluence of the Parlung Tsangpo and Layuequ to the vicinity of Dexing Township, with ten sampling sites established along the transect. Using digital image analysis, two-dimensional shape parameters were extracted from over 36,000 individual particles. Multivariate statistical techniques, including Principal Component Analysis (PCA) and Factor Analysis (FA), were applied to identify three physically meaningful composite factors. The spatial and sediment size dependent patterns of these factors revealed that: (a) coarser particles, relative to finer ones, exhibit reduced mobility and longer residence times within the channel. Prolonged exposure to hydraulic abrasion and inter-particle collisions leads to lower saturation but higher smoothness, while lithologically homogeneous coarse sediments display greater strength and a more equant morphology compared to finer fractions; (b) abundant sediment supply largely preserves source-derived particle shapes, whereas variations in fluvial conditions along the transect dominate shape modification. For example, confluences reduce flow velocity, promoting particle deposition and prolonged in-channel exposure, thereby enhancing smoothness. Higher smoothness observed in the mainstem relative to tributaries indicates more intense flow and faster abrasion in the main channel.This study established relationships between particle shape, fluvial processes, and sediment supply through field investigations, providing a reference for future research in sediment dynamics.

本研究针对当前颗粒形态特征与河流动力学及沉积物补给过程之间关联研究的空白展开。本次野外调查于人迹罕至的雅鲁藏布大峡谷（Yarlung Tsangpo Grand Canyon）开展，调查范围覆盖帕隆藏布与拉月曲汇流口至德兴乡附近区域，沿调查样带共布设10个采样点位。通过数字图像分析技术，从逾36000颗单个颗粒中提取二维形态参数。采用主成分分析（Principal Component Analysis, PCA）与因子分析（Factor Analysis, FA）等多元统计方法，共识别出3个具备物理意义的复合因子。上述复合因子的空间分布规律与沉积物粒径依赖特征显示：(a) 相较于细颗粒，粗颗粒的河道移动性更弱，在河道内的停留时间更长。长期经受水力磨蚀与颗粒间碰撞作用，使其棱角饱和度更低但光滑度更高；而岩性均一的粗颗粒沉积物相较于细粒组分，具备更强的结构强度与更趋近于等轴的形貌；(b) 充足的沉积物补给可较大程度保留颗粒的源区形貌特征，而调查样带沿线河流动力条件的差异则主导了颗粒形貌的改造过程。例如，汇流区域会降低水流流速，促进颗粒沉积并延长其在河道内的暴露时间，进而提升颗粒光滑度。相较于支流，主河道内观测到的颗粒光滑度更高，这表明主河道内水流作用更强、磨蚀速率更快。本研究通过野外调查建立了颗粒形貌、河流过程与沉积物补给之间的关联，可为未来沉积物动力学领域的相关研究提供参考依据。