The planform evolution of tidal meanders is driven by interactions between channel morphology and periodically reversing tidal flows, which feed back into the development of erosional and depositional patterns. However, the paucity of quantitative data has so far undermined detailed analyses about the geomorphic effects of tidal flows within tidal meanders. Here we aim to bond the morphodynamic evolution of tidal meanders with the structure of three‐dimensional flow that shapes them. By means of an acoustic Doppler current profiler, we have surveyed the flow fields over three different tidal meandering channels in the salt marshes at San Felice (Venice lagoon, Italy), each characterized by distinct planform morphology and evolutionary dynamics. Mutually evasive paths followed by the maximum ebb and flood streamwise velocities determine periodic changes in both the position and the orientation of curvature‐induced cross‐stream flows. These secondary flows can be locally disrupted by patches of submerged vegetation, especially in meanders of small size, with direct implications for the morphodynamic evolution of meander bends. The latter is further affected by flow separation in sharp bends. Flow separation effectively reduces channel width, enhancing bank erosion due to increasing flow velocities. Moreover, it creates low‐velocity zones of recirculating flows at both the inner and outer banks, thereby promoting the formation of point bars and concave‐bank benches, respectively. By relating three‐dimensional flow structure to patterns of channel change, our results provide a first step to unravel the relation between flows and forms within tidal meanders, whose planform characteristics may differ greatly from their fluvial counterparts.

中文翻译：

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潮汐蜿蜒通道的三维流动结构和形态动力学演变

潮汐弯道的平面状演化是由河道形态与周期性逆流之间的相互作用驱动的，这些相互作用会反馈到侵蚀和沉积模式的发展中。但是，迄今为止，定量数据的匮乏破坏了对潮汐弯道内潮汐流地貌影响的详细分析。在这里，我们旨在将潮汐河床的形态动力学演化与塑造它们的三维流动结构联系起来。通过声学多普勒电流剖面仪，我们调查了圣费利切（意大利威尼斯泻湖）盐沼中三个不同潮汐蜿蜒通道的流场，每个通道都具有独特的平面形态和演化动力学。互为回避的路径以及最大的潮汐速度和洪水泛滥的速度决定了曲率引起的横流的位置和方向的周期性变化。这些次生流可能会被淹没的植被斑块局部破坏，尤其是在小规模的河曲中，这直接影响到河曲弯的形态动力学演化。后者进一步受到急弯中流动分离的影响。流动分离有效地减小了通道宽度，由于流速增加而加剧了堤岸侵蚀。此外，它在内河和外河两岸都形成了低速循环流区域，从而分别促进了尖杆和凹岸台的形成。通过将三维流动结构与渠道变化模式相关联，