Abstract This paper is an attempt to quantify the plausible time scales of clastic sediment supply variations at the entrance of sedimentary basins. Our approach is based on the sedimentary system concept, which simplifies natural systems by dividing them into three zones of dominant processes: the erosion, the transfer, and the sedimentation subsystems. We examine recent results from geomorphology, which show that frequent climate changes can induce high-frequency sediment flux variations at the outlet of the source area. We put forward the crucial role of the transfer subsystem, which conveys sediment from the erosion zone to the basin. By applying a diffusive model to a number of worldwide rivers, we extend from large (>1000 km) to intermediate (>300 km) rivers the previous finding that the transfer subsystem acts as a buffer for short periods sediment pulses (tens to hundreds of kiloyears). This implies that high-frequency stratigraphic cycles in clastic accumulations fed by large drainage systems are unlikely to reflect sediment supply cycles of tens to hundreds of thousands of years of periodicities.