Tidal network ontogeny: Channel initiation and early development

The long- term morphological evolution of tidal landforms in response to physical and ecological forcings is a subject of great theoretical and practical importance. Toward the goal of a comprehensive theoretical framework suitable for large- scale, long- term applications, we set up a mathematical model of tidal channel network initiation and early development, which is assumed to act on timescales considerably shorter than those of other landscape- forming ecomorphodynamical processes of tidal systems. A hydrodynamic model capable of describing the key landforming features in small tidal embayments is coupled with a morphodynamic model which retains the description of the main physical processes responsible for tidal channel initiation and network ontogeny. The overall model is designed for the further direct inclusion of the chief ecomorphological mechanisms, e. g., related to vegetation dynamics. We assume that water surface elevation gradients provide key elements for the description of the processes that drive incision, in particular the exceedance of a stability ( or maintenance) shear stress. The model describes tidal network initiation and its progressive headward extension within tidal flats through the carving of incised cross sections, where the local shear stress exceeds a predefined, possibly site- dependent threshold value. The model proves capable of providing complex network structures and of reproducing several observed characteristics of geomorphic relevance. In particular, the synthetic networks generated through the model meet distinctive network statistics as, among others, unchanneled length and area probability distributions