The largest deltas on Earth are tide‐dominated with multiple distributaries, which can experience different forcings. Yet, most observational studies of sediment dynamics in these systems focus on a single distributary. Comparison of the tidal‐to‐estuarine reaches of three representative distributaries of the Ayeyarwady Delta, Myanmar highlights the variability in sediment retention and export within a megadelta. The Ayeyarwady River has no mainstem dams, providing an opportunity to examine a relatively natural, monsoon‐dominated system. Observations were collected during high flow (September 2017) and low flow (March 2018 and 2019). The eastern Yangon distributary empties into the sheltered Gulf of Mottoma while the central Bogale and western Pathein distributaries are exposed to seasonal waves. During high flow, suspended‐sediment concentration (SSC) was consistent across all three distributaries (0.2–0.4 g/L). The upper delta retained 20%–60% of the mainstem sediment load, while the lower distributaries were tidal rivers exporting sediment. During low flow, the lower distributaries were partially mixed estuaries with little net discharge. However, SSC increased to >1 g/L in the Yangon distributary, remained constant in the Bogale distributary, and decreased in the Pathein distributary compared to high flow. This difference was driven by offshore sediment supply; fine sediment is retained near the mouth of the Yangon and advected away from the Pathein distributary. Consequently, nearshore sediment residence time in monsoon‐influenced megadeltas is controlled by coastal orientation, the timing of discharge with respect to ocean conditions, and tidal amplification. Changes to fluvial sediment delivery can cause non‐uniform coastal impacts due to these differing distributary processes.

中文翻译：

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将潮汐主导型三角洲中的泥沙淤积与分水道水动力和泥沙动力学联系起来：缅甸伊洛瓦底三角洲

地球上最大的三角洲是由多个分水岭控制的，这些分水岭可能经历不同的作用力。但是，大多数对这些系统中沉积物动力学的观测研究都集中在一个分配器上。缅甸伊洛瓦底三角洲三个代表性支流的潮汐到河口范围的比较突出了一个大三角洲内的沉积物保留量和出口量的变化性。伊洛瓦底江（Ayeyarwady River）没有大坝，这为检查相对自然，季风为主的系统提供了机会。在高流量（2017年9月）和低流量（2018年3月和2019年）期间收集了观测值。仰光东部的支流排空到庇护的Mottoma海湾，而中部的Bogale和西部的Pathein支流则暴露在季节性的海浪中。在高流量期间 悬浮沉积物浓度（SSC）在所有三个分流器中均保持一致（0.2–0.4 g / L）。上三角洲保留了主干沉积物负荷的20％–60％，而下三角流则是输出沉积物的潮汐河。在流量低的情况下，较低的分流河段是部分混合的河口，净流量很少。但是，与高流量相比，仰光分流器中的SSC增加到> 1 g / L，在Bogale分流器中保持恒定，在Pathein分流器中减小。这种差异是由近海沉积物供应驱动的；细小的沉积物被保留在仰光河口附近，并从Pathein分流处平移。因此，季风影响的大三角洲中近岸沉积物的停留时间受沿海方向，与海洋条件有关的排放时间，和潮汐放大。由于这些不同的分配过程，河流沉积物输送量的变化会导致不均匀的沿海影响。