Figure 4 . Representative time slice of transient evolution for Case 1 (uniform decrease in rainfall) and Case 2 (uniform increase in rainfall) through (a)ksn -Eavg and (b)ksn-q -Eavg parameter spaces. Case 1 is shown in red shaded domain (transient decrease in erosion rate, E < U ), and Case 2 is in blue shaded domain (transient increase in erosion rate, E> U ). Curves expressing the expected steady state relationship between channel steepness and erosion rate with different uniform erosional efficiencies are shown; K = Kp , is shown in black solid line, and grey lines show different values ofK as multiples of Kp . Vertical dashed lines show percent deviations from steady state erosion rate. Initial and final conditions shown with yellow circles, as labelled. Model data from different positions along the trunk profile and individual tributaries shown with red and blue data points, respectively. Trunk data shown are only profile nodes at tributary junctions – all trunk profile datapoints have a corresponding tributary datapoint at the same position. Trunk profile data show upstream mean values from their respective position, and tributary data show mean values for the tributary profile measured at the junction with the trunk profile.