Riccardo Bonanomi

Meandering rivers are single channel rivers that are usually found in the latter parts of river basins. Even in remote areas, such rivers are more and more affected by climate changes and anthropogenic stressors Modelling has always been one of the preferred method to investigate the planimetric evolution, due to its long timescale and the remoteness of free-flowing meandering rivers. One of the most common approaches uses a constant base flow with a superimposed analytical solution for the flow field forced by the curvature distribution. The planimetric evolution is then derived by the some characteristic of said flow field and the sinuosity of the planform is used to update the base flow. This has the advantage that can easily represent the influence of the curvature on the flow field, but the use of a constant flow field for the whole reach and its update method can lead to issues when representing the evolution of the bankfull geometry and cannot represent properly the spatial variability seen in real rivers.

The idea is then to develop a new modelling framework that is able to represent both the effects of the curvature and the spatial variability of the bankfull geometry using an Exner-based base flow parameters update. This is key to analyse the effects of the changing sediment and water supply that can be caused by climate change and human intervention.

We are developing a model that will combine the curvature induced effects on the flow field with the spatial variability and a more physically based temporal evolution of the bankfull geometry parameters. We are also using satellite data to validate the model results.

Up until now we analysed the existing approach to understand how to implement the new base flow update approach and how to characterize the steady state bankfull geometry and planimetric configuration. We also compared the model results with real rivers data from satellite and from literature. We developed a simplified model with the new base flow update, with the periodic solution for the flow field, to understand how to treat the boundary conditions at the interface between reaches with different parameters, to understand how to introduce the non-periodic solution in the coming months. Finally, we will introduce alterations of the sediment and the water supply, to evaluate the effects of climate change and anthropogenic stressors.