Gabriele Barile, Ph.D. Candidate 37th cycle, University of Trento, DICAM

River bifurcations play a crucial role in determining the downstream partitioning of water and sediment in a variety of fluvial environments, such as river deltas, braiding or anastomosing rivers, and alluvial fans. As highlighted by several analytical, numerical, and experimental studies, the unstable character of bifurcations often leads them to distribute water and sediment unevenly among the downstream branches. Highly unbalanced states can be seen even in the case of symmetric planform configuration and steady boundary conditions and may result in the complete closure of one of the two anabranches. While previous studies mainly focused on the degree of asymmetry shown by bifurcations at their equilibrium states, as a Ph.D. candidate I’m addressing the transient behavior of bifurcations and their response to geometrical constraints and time-dependent boundary conditions.

Specifically, my work of research during the three years of the Ph.D. program is structured as follows:

• By means of a novel, quasi-1D numerical model (represented in Figure 1) I started developing during my MSc thesis, I’m going to explore the transient behavior of a simplified river bifurcation, both with steady and unsteady boundary conditions. The aim of this work is to identify the key features of bifurcations that govern their autogenic instability mechanism and determine their response to external forcings such as variable water discharge and downstream water level.
• Using an analytical formulation, I have studied the equilibrium configurations and evolutionary timescales of bifurcations whose branches show a relevant difference in channel width. This problem is particularly relevant for the optimal design of longitudinal training dams (see Figure 2), an emerging engineering approach to increase the habitat availability of rivers while preserving their navigability. I plan to compare the analytical findings against the results of experiments carried out on a laboratory-scale physical model.