Field observation of rapid tidal meander migration on muddy flats

Tidal meanders are ubiquitous features of coastal ecosystems, controlling the exchange of water, sediment, and nutrient fluxes therein. The outer banks of tidal meanders typically undergo bank collapses, primarily triggered by the alternating actions of in-channel currents and seepage flow during periods of tidal exposure. As a result, tidal meanders frequently migrate across muddy flats, leaving substantial footprints of cutoff events. However, few studies have to date delved into this topic, primarily due to the challenge in obtaining high-resolution data to analyze their migration behavior. Here, we present field observations from the Jiangsu coast, China, to quantify tidal meander migration and its impact on planform geometry. During successive low tides, we apply UAV-based LiDAR to obtain centimeter-level DEMs of a main channel reach (~300 m wide) and its branching channels (~10 m wide). Unlike the relatively stable planform morphology commonly reported for salt marsh channels, we observed rapid lateral migration on silty flats (~10^-3 m/s), leading to frequent cutoff formation. These observations highlight the highly dynamic nature of tidal meanders on muddy flats and underscore the role of bank collapse in shaping tidal-channel planforms. Our findings have important implications for understanding tidal-channel morphodynamics and associated eco-geomorphic feedbacks, including sediment redistribution and potential carbon release in coastal wetlands.