On the Morphodynamic Equilibrium of a Short Tidal Channel

We set up a two-dimensional modeling framework to explore the development and the equilibrium configuration of a tidal channel. We consider two types of morphodynamic modeling systems coupling different flow and sedimentation models, to study the feedback mechanisms controlling the morphodynamics of tidal channels. The simulations indicate that the tidal channel first experiences a pseudo equilibrium state, then diverges from it, and finally approaches a dynamic equilibrium. The reason for this behavior is demonstrated analytically using linear perturbation analysis. We identify distinct positive and negative feedbacks that lead the tidal system to a dynamic equilibrium. One of the feedback mechanisms is controlled by the flow momentum balance, while the other one depends on the overall sediment balance. The dynamic equilibrium configurations obtained in the numerical simulations compare favorably with the theoretical equilibrium. Deviations from theory can be explained analyzing the assumptions in the flow and sedimentation models. Moreover, the minimum width-to-depth relationship of a tidal channel cross section is derived and is found to be in agreement with field measurements.