The fractal geometry of tidal-channel systems in the Dutch Wadden Sea

Horton's hierarchical and fractal analysis of channel circumference reveals that tidal-channel systems in the Dutch Wadden Sea have similar branching patterns. Channel systems have the same characteristics as three- to four-t imes branching networks. The branch lengths of these channels decrease loga rithmically. The channel systems can be regarded as 'statistical self-simil ar fractal' networks, considering the natural variability in branch lengths and channel positions. Branching of channels does not continue below the 5 00 m scale. The channel-system circumference length is logarithmically rela ted to the tidal prism and drainage area. The similarity of the channel sys tems, regardless of their size, relative amount of intertidal flats, and ti dal amplitude, points to a self-organising nature. All processes depend on the feedback between morphology and hydrodynamics. At first sight, the chan nel systems can be regarded as an ebb-driven drainage network, governed by erosion. However, flood-dominated net sedimentation occurs in large parts o f the drainage basins and modifies the ebb-driven network. The complex inte raction of hydrodynamic and morphodynamic processes in tidal basins limits the applicability of process-based models. Behaviour-oriented modelling has a wide applicability and can be improved using the fractal geometry as the dynamical equilibrium morphology. The fractal-network geometry can also be used for stochastic reconstructions of fossil tidal-channel systems, when only limited observations are available.