Schematic illustrations of the experimental devices. (a) Surface view for the experiment with two slope breaks (solid red lines) and involving three plates (P1, P2 & P3); the dashed red line shows the location of the axial cross-sections. (b,b’) Cross-section views of the device for the experiments with one slope break (two plates of different lengths, P1 & P3). (c) Cross-section views for the experiments with two slope breaks (see (a)). (b,c) The vertical exaggeration is x8. The red triangles show the location of the slope breaks (SB1 and SB2).