Autogenic knickpoints in laboratory landscape experiments

Abstract. The upstream propagation of knickpoints in river longitudinal profiles is commonly assumed to be related discrete changes tectonics, climate or base level. However, the recognition that some may form autogenically, independent any external perturbation, challenge these assumptions. We investigate here genesis and dynamics such autogenic laboratory experiments at drainage basin scale, where landscapes evolved response constant rates level fall precipitation. Despite forcings, we observe regularly initiate rivers catchments' outlet throughout duration experiments. knickpoint rate does not decrease monotonically relationship with area, as predicted by stream-power-based models, instead first increases until mid-part catchments before decreasing. To knickpoints, calculated hydraulic information (water depth, width, discharge shear stress) using a hydrodynamic model. show initiation coincides fairly abrupt narrowing entailing an increase their stress. Then, once have propagated upward, widen causing stress incision rate, making less than rate. This creates unstable situation which drives formation new knickpoint. suggest autocyclic model generation controlled width variations tectonics. questions interpretation landscape records focusing only on tectonic without considering processes.