High variability in flood discharge and stage accelerates river mobility

Lateral channel migration is a fundamental process in natural alluvial rivers; however, the factors that control the rate of migration remain unclear. Despite its importance in shaping river morphology, the impact of water discharge on river mobility is still largely unexplored. Here, we leverage a dataset of 64 rivers across the globe to show that higher variability in river discharge and stage promotes higher rates of river migration. To reveal the physical processes behind this relationship, we focused analyses on the lowermost 500 kilometers of the Mississippi River, where a pronounced gradient in water stage variability and migration rate exists. We demonstrate that stage variability affects channel mobility by influencing the sediment size of riverbanks and thereby controlling riverbank erodibility. These results can be used to predict river responses to climate change and decipher past hydroclimates using stratigraphy from Earth and Mars.