Competing Feedback in an Idealized Tide-Influenced Delta Network

The morphodynamic evolution of river deltas is intimately tied to fow and sediment partitioning at bifurcations. In this work, the long-term equilibrium confguration of a simple delta network is investigated by means of an analytical model, which accounts for the efect of small tidal oscillations. Diferently from individual bifurcations where tidal action is always a stabilizing factor, in the case of a tree-like delta with multiple bifurcations a dual response emerges. Specifcally, depending on the values of four reference parameters functions of tidal amplitude, upstream fow conditions, and channels geometry, tides can either promote or discourage an unbalanced discharge distribution. This behavior primarily concerns the apex bifurcation, which is afected by the variations of the relative tidal amplitude at the internal nodes. In turn these variations depend on how fow and sediment are diverted upstream. The stability of steady-state solutions is found to be governed by the sign and magnitude of the slope asymmetry between channels. This work provides a basic modeling framework for the interpretation of the autogenic response of multiple coupled micro-tidal bifurcations, which can potentially be extended to include in a unifed scheme erosional and depositional processes typical of fuvio-deltaic systems.