While crossing the Rio Randice the walker can observe that it no longer flows on the surface of the fan, but has eroded the materials it had deposited itself. The stream flows in an incision that deepens towards the valley, creating slopes up to 40 m high. This is because – following the stage of deposition and formation of the alluvial fan (beginning in the Middle Ages) – an erosive phase began that is still continuing. Along the incision some groynes have been placed that serve to decrease the slope of the riverbed, thus reducing the speed of the waters and their erosive power.