Evolution of the streamline morphology. The top row shows the data from the experiments. Two sets of streamlines correspond to = 0.7 and = 1.1 (left). Below * = 0.8, they are crumpled and segregated. Above *, they are nested and persistent. Corresponding topographic maps (right) ( Methods ). Below *, the segregation of streamlines translates in a two-level topography. Above *, the map features high hills and deep valleys. The bottom row shows data from the numerical simulations. Streamlines and topographic maps are predicted by the equilibrium configurations of the Hamiltonian defined by equation ( 1 ) for J C = -2 and J C = +2. The qualitative agreement between the simulations and experiments confirms the relevance of our active hydraulics laws. J C is a good proxy for the channel aspect ratio.
