Morphometry of widespread tidal meander cutoffs discloses similarity to fluvial morphodynamics

Similarities in planform dynamics between tidal and fluvial meandering channels contrast with the apparent lack in coastal wetlands of lateral-migration features like meander cutoffs and oxbow lakes, which led to the broad interpretation that tidal and fluvial meanders differ morphodynamically. We analyzed meander neck cutoffs from diverse tidal and fluvial environments worldwide, and show that tidal cutoffs are more widespread than believed. Their perceived paucity is a figment of coastal-wetland pronounced drainage density and hydrological connectivity, coupled with reduced size of most tidal channels and dense vegetation cover. Whereas these factors do not efface tidal meander cutoffs, they collectively inhibit oxbow-lake formation and render tidal cutoffs ephemeral, hardly detectable geomorphic features. We thus argue that similar morphodynamic processes drive cutoff formation in tidal and fluvial landscapes, with differences arising only during post-cutoff evolution. This bears important implications for understanding the ecomorphodynamics of coastal wetlands and predicting their long-term evolution.