A simple transport rate relation that unifies aeolian and fluvial nonsuspended sediment transport

Nonsuspended sediment transport driven by streams of liquid or air is an important driver of the morphodynamics of planetary landscapes, seascapes, and riverscapes. Laboratory and field measurements of the sediment transport rate as a function of the fluid shear stress have enabled us to predict such processes with reasonable accuracy on Earth. However, sediment transport is also ubiquitous in extraterrestrial environments, such as on Venus, Mars, Titan, and occurs possibly even on Pluto. This raises the question of whether we can extrapolate transport rate expressions validated with measurements on Earth to extraterrestrial environments. The answer is probably, yes, but only if the used expressions capture the essential physics. Here, using coupled DEM/RANS numerical sediment transport simulations, we show that nonsuspended sediment transport in a large range of aeolian and fluvial environments has a conceptually simple common physical underpinning that allows treating these different transport regimes in a universal manner. That is, a conceptually simple universal model captures simulated and measured transport thresholds and transport rates. In particular, when the transport layer thickness substantially exceeds the viscous sublayer thickness (true for many environments), this model yields a mathematically simple transport rate expression that agrees, simultaneously, with existing measurements in air and water.