Using a stereo pair of HiRISE images of a pole-facing crater slope at 38°S, 218°E, we measure topographic profiles along nine gullies. Typical slopes of the interior channel region (above the depositional apron) are ∼20°. We test the hypothesis that sediment transport on gully slopes occurs via fluvial transport processes by developing a numerical sediment transport model based on steep flume experiments performed by Smart (1984). At 20° slopes, channels 1 m deep by 8 m wide and 0.1 m deep by 3 m wide transport a sediment volume equal to the alcove volume of 6 × 105 m3 in 10 h and 40 days, respectively, under constant flow conditions. Snowpack melting cannot produce the water discharge rates necessary for fluvial sediment transport unless long-term (kyr) storage of the resulting meltwater occurs. If these volumes of water are discharged as groundwater, the required aquifer thicknesses and aquifer drawdown lengths would be unrealistically large for a single discharge event. More plausibly, the water volume required by the fluvial transport model could be discharged in ∼10 episodes for an aquifer 30 m thick, with a recurrence interval similar to that of Martian obliquity cycles (∼0.1 Myr).