This study examines the spatial pattern of fractional sediment mobility and assesses the influence of morphologic units on bedload transport in a small pool-riffle reach with limited supply. Using a 2D hydraulic model and a subsurface-based sediment transport model, shear stresses, fractional sediment mobility, and bedload transport were examined for flow events ranging in magnitude between 0.2Q_bf and 1.5Q_bf. Results reveal that while spatial variations in shear stress decrease as discharge increases, only a small proportion of the bed experiences high transport rates. At the reach scale, riffles are the primary morphological unit contributing to fully mobile sediment for all size fractions. However, at a subunit scale, there is evidence of sediment transport reversal for grains >32 mm at flows near or exceeding bankfull discharge in association with shear stress reversal. These transport reversals are important for maintaining pools despite their infrequent occurrence in the study reach. Sediment transport maps indicate that bed morphology considerably influences sediment transport at low to moderate flows. During these events, the shear stress is sensitive to local bed topography and partial mobility is the dominant transport process. In contrast, variations in bedload transport rates decrease during high flows when the flow is less sensitive to variations in bed topography and the bed becomes fully mobile.

中文翻译：

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评估形态单元对小池浅滩河段泥沙分流度和床质输送的影响


本研究考察了沉积物分数迁移率的空间模式，并评估了形态单元对供给有限的小型水池浅滩河段底泥输送的影响。使用二维水力模型和地下沉积物输送模型，检查了大小在 0.2Q _bf 和 1.5Q _bf