Global sediment transport intermittency is set by river planform

Jonah S. McLeod , Vamsi Ganti, Gary J Hampson, Rebecca E. Bell, Louise J. Slater , Yinxue Liu, Huck C. Rees, Alexander C Whittaker

Patterns of water and sediment flux in rivers are key to understanding landscape responses to environmental change. Quantifying water intermittency in rivers (from perennial to ephemeral) provides vital context for interpreting long-term hydrographs and flood frequency, yet controls on corresponding sediment intermittency are poorly understood due to measurement challenges. We present the first global dataset quantifying both water and sediment intermittency in >300 river reaches across all climate zones. Results reveal water and sediment intermittency are decoupled worldwide: sediment intermittency is primarily controlled by river planform (R^2=0.47, <10-3), the plan-view morphology of rivers encompassing sinuosity and channel-count, while water intermittency is set by climate. We provide a mechanistic framework explaining the global variability in water and sediment intermittency, demonstrating that river planforms buffer climate-driven discharge variation and dampen these signals in sedimentary deposits. Our results permit stronger constraints on the impacts of intensifying hydrological variability in the near future, and the timescales of river activity across the solar system.