Compared to gravel and sand sorting, sorting process of in the fine-grained rivers with fine sand and silt beds is relatively less discussed, of which underlying mechanism and implications are under debate. In this talk, we focus on the phenomena and implications of silt-sand sorting, especially on their influence in the sediment load and river morphology. We first show that the sediment load at the median grain size around 125 microns exhibits ultra-sensitivity to the gradation coefficient of bed grain size, where up to 2 orders of magnitude change in sediment load (high vs low transport regimes) may arise due to slight change in gradation coefficient (non-uniform vs uniform sediment), suggesting the importance of grain sorting. We develop grain size specific transport formulae for each transport regime and illustrate that selective entrainment of silt to fine sand particles can result in downstream fining of bed grains in the silt-rich rivers. However, discrepancies arise when reconciling the transport capacities of the two regimes for sediment within overlapping grain size ranges, necessitating novel physical explanations. Furthermore, we explore the potential implications of these phenomena, such as their impact on river delta morphology.