As part of the European Space Agency (ESA) ExoMars programme, the Rosalind Franklin rover is planned to launch in 2028 to investigate mineralogical and chemical properties of the shallow subsurface and to search for biosignatures. The rover will land in Oxia Planum, chosen for its clay-rich units and evidence of water-related activity dating back approximately 4 billion years. Imagery of the landing site has revealed an ancient river delta in the southeast, the deposits of which can give insight into environmental conditions and flow characteristics at the time of formation. Specific to the ExoMars mission, delta sediments have potential to preserve biosignatures if present. To study the Oxia Planum delta, we employ numerical modelling using the Delft3D D-Flow FM hydro-morphodynamic suite. Building on the theoretical knowledge, we investigate how delta evolution varies on Earth and Mars under different gravities and sediment densities. We show that all else equal, Martian deltas are larger and experience higher volumes of sediment transport, with variable differences in morphology. We then simulate the evolution of Wax Lake Delta in Louisiana, USA—a microtidal delta of a similar size to the Oxia Planum delta. We note that while the model realistically reproduces hydrodynamics and short-term morphologic change, it less successfully simulates longer-term morphologic change and is most sensitive to parameters such as grain size and channel roughness. We apply this learning to model the Oxia Planum delta, with the goals of constraining past flow conditions and identifying possible locations within the delta remnants to search for biosignatures.