We describe the evolution of an ∼600-m-deep tributary outflow channel to Ares Vallis, Mars. High-resolution topography, image analysis, and crater statistics indicate that this tributary canyon developed by the upstream migration of a large, ∼300-m-tall cataract during multiple flood events that span ∼1 b.y. of Mars history (3.7–2.6 Ga). Issuing from Hydapsis Chaos, these floods were initiated at a similar time and occurred over a similar time range to flooding in Ares Vallis, suggesting a potential regional control on flood initiation and chaos formation. In addition, we provide evidence that cataract retreat and significant incision within the tributary canyon occurred only after a series of downcutting events within Ares Vallis. Topography data and crater statistics taken from the floor of Ares Vallis indicate an ∼300 m base-level drop that coincides temporally with an Early Amazonian (ca. 2.6 Ga) flood event and cataract formation within the tributary canyon. The results both confirm the hypothesis of long-term, multiple flood events within martian outflow channels and demonstrate the influence of base-level change on their incision.