LAUSR

Significance Meandering tidal channel networks play a central role in the ecomorphodynamic evolution of the landscapes they cut through. Despite their ubiquitous presence and relevance to sedimentary and landscape features, few observations of tidal-meander evolution exist, and we lack a full understanding of the governing processes. Field analyses show that tidal meanders, traditionally viewed as stable landscape features, display modes of migration and migration rates per unit width quite similar to those characterizing their fluvial counterparts, with important implications for the characterization of the related sedimentary products. The results presented here contribute to our understanding of the morphological evolution of tidal landscapes. The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths.