Mechanisms for sediment fining in a side channel system

Side channels have been constructed in the Dutch river system to reduce flood risk and to increase the ecological value of the river. Some of these side channels show large aggradation and therefore require regular maintenance. Grain size measurements of the deposited sediment show that the bed of the side channel contains much finer sediment (0.2-0.3 mm) than the bed of the main channel (1-2 mm). This suggest that sorting occurs at the bifurcation of the side channel which likely affects the equilibrium state and the time scale of the side channel development. The objective is to reproduce the morphodynamic development with a 2D numerical model that allows for sorting processes. The dimensions of the system are based on the Waal River in the Netherlands.