Butterfly effect in a deterministic ecomorphodynamic model

The eco-morphodynamic trajectory of rivers is dictated by the non-linear complex interactions among riparian vegetation, flow and sediment transport. Because of its non-linear dynamical nature, complexity can emerge from the model governing such interactions. The goal of this work is to investigate and quantify such complexity that could limit predictions of the river morphological trajectories. To this end, we conduct numerical simulations using a 1D deterministic model that couples hydro-morphodynamics with vegetation dynamics. We consider a straight channel with a vegetated patch perturbed periodically by a succession of triangular floods of constant amplitude. Vegetation growth occurs in between of two consecutive floods, and it may be uprooted during flood events. During the analysis we change the ratio between the flood frequency and the vegetation growth. Model results demonstrate that the response of the system can be chaotic, limiting the long-term predictability of the system to few flood events.