Abstract

Field experiments were conducted at Tiramoana station, 30 km north of Christchurch, New Zealand. Experimental erosion plots 16.5 m long, 0.6 wide and with a slope inclination of 14 -14.5° aimed to measure the variability of flow velocity and sediment transport rate in shallow flow using a high-speed digital video camera and image analysis. All six flow runs (0.5-3.0 l/s discharge) exhibited supercritical and laminar flow; hence actual velocity varied more than in turbulent flow and the power spectrum was of ‘red-noise’ type. Sediment transport rate had an even higher variability, with distinct differences between the dynamics of small and large aggregate groups.

Keywords: high-speed digital video; image analysis; flow velocity variability; sediment transport variability