AbstractBedload transport measurements in two upland streams are considered as a function of the excess stream power exerted on the bed by the flow.During low flows when the framework gravels remain undisturbed, fine sediments are winnowed from the bed‐surface layer once a threshold of 3·4 W m−2is exceeded and the transport rate is strongly supply limited. However for stream powers in excess of 15 W m−2framework gravels are mobilized and the efficiency of the transport process approaches a local maximum of about 1 per cent for discharges up to 2/3 of bankfull.An inverse depth dependence in the efficiency of the transport process was noted but although bedload calibre increased as a function of discharge its influence on efficiency could not be demonstrated. However it was suspected that the size‐sorting relationships of the bed‐material in a number of rivers in relation to the transport efficiency might profitably be examin