­Figure 6 . Transient evolution of the trunk profile (a & c) and network of tributaries (b & d) in Case 4 (spatially uniform to top-heavy) throughksn -Eavg (a & b) andksn-q -Eavg (c & d) parameter spaces; figure layout is same as Figure 5. Like Case 3, the trunk response is muted relative to the network of tributaries, but the disparity is more extreme in this case. Star in panel (a) shows Kcalculated from equation (1b) based on the final mean rainfall of 1 m/yr (K = Kp ) at steady state, which corresponds to a predicted mean ksn of ~450. Again, note offset between this value and range of erosional efficiency and ksn values exhibited at t6.