Hello,

I have a question regarding the maximum erosion values that can be obtained in long-term simulations using the 1D model of the Rhine branches. I've run a simulation of 100 years to gain insight in the autonomous bed degradation of the Rhine branches. In this simulation, the upper section of the Waal (around the fixed layers near Erlecom and Nijmegen) shows an average main channel bed degradation (BL_avg) of 4.0 meters. The maximum degradation value (BL_mor) is more than 6.0 meters. I was wondering how this is possible, given that the total thickness of the top layer and underlayers in the model seems to be equal to 4.1 meters?

How exactly do bed level changes and the use of underlayers work? Are they coupled? Or are the layers used to calculate sediment transport and keep constant thickness but a varying composition? (And what happens to the active layers thickness if the total thickness of all remaining layers is less than 1.0 meters?)

Kind regards,
Thorvald Rorink