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Objective The discharge rate regulates the sedimentary evolution and morphological scale of a braided river. In this study， the influence of discharge rate on the formation of braided channels， bars and internal sedimentary architecture is systematically analyzed for the first time. Methods Five groups of three-dimensional sedimentary numerical simulation experiments with different flow rates were carried out using Delft3D software to explore the evolution， morphological patterns and scale differences of braided channels and bars formed as a result of various flow rates. The models reproduce the internal architectural patterns of a range of bars developed in braided rivers with different flow rates and summarize the sedimentary characteristics and evolution of sandy braided rivers. Results （1） The rate of discharge is positively correlated with the sedimentary evolution of braided rivers. Low-discharge braided rivers exhibit limited evolution， in which bars mainly tend to migrate vertically and are less dissected by channels. By contrast， high-discharge braided rivers undergo intensive evolution， characterized by lateral migration and frequent dynamic equilibrium processes involving compound bars and dissection. （2） The discharge rate influences the plane pattern and channel depth of braided channels. As discharge increases， the braided channel becomes wider and deeper， resulting in a reduced overall number of channels but more highly developed chutes of the channel bars. Lower-discharge braided channels are shallower and primarily consist of numerous narrow， relatively fixed interwoven river networks. （3） Discharge further governs the co-evolution of channels and bars. Greater discharge enhances bar complexity， promoting the development of large complex compound bars and side bars with intricate internal stacking relationships and more frequent chutes. （4） Despite strong spatial heterogeneity in the internal architecture of channel bars in sandy braided rivers， consistent patterns emerge： all bars develop downstream accretions （DA） in the core， vertical accretions （VA） layered above， and lateral accretions （LA） deposited at the sides. A key distinction lies in the increased proportion of LA at higher discharge conditions. （5） Discharge correlates positively with accretion size but inversely with aspect ratio and flakiness ratio. Median aspect ratios of bars are 3.5 in low-discharge systems versus 4.5 in high-discharge systems. Conclusions The study proposes a positive correlation between discharge and the scale of channel bars and accretions in sandy braided rivers. This clarifies flow-controlled sedimentary characteristics and scale variations， providing a basis for analyzing complex subsurface reservoir architectures.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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