Abstract: Throughflow has been measured from three soil horizons on a 12 slope with impermeable, bedrock. Storm flow comes from the 10–45 cm horizon and is controlled by the upslope extent of saturated conditions. Base flow comes from the 45–75 cm horizon and is supplied by slow unsaturated flow from the whole soil mass to a small constant zone of saturation. Differences between input and output stream hydrographs over 270 metres of channel are attributed to throughflow and correlate well with measured values providing a basis for separating throughflow components from the stream hydrograph. Observed stream flows contain no overland flow or ground water flow components. The main basin flood peak is not generated within this control section of channel but is produced in the headwater zone (0.1 km2) by the faster runoff characteristics of the soils in that area and by topographic factors which lead to rapid channel extension.