The feasibility of' model testing to rate Cut-throat flumes is examined for a particular prototype structure. A model of the structure was built to a scale of I : 7.3 and a rating curve obtained. This rating was tested by examining its prediction of actual storm events against measurements of the same storm events obtained with an HL-flume situated immediately downstream of the prototype structure. The results verify the use of model testing to rate Cut-throat flumes. Examination of the results in the light of previous studies indicates the critical importance of modelling the entrance conditions to the flume as well as the flume itself and reveals the significance of boundary layer scale effects, particular at low flows. The measured piezometric head is shown to be significantly dependent on the elevation of the tapping point and illustrates the need to reproduce the precise tapping point location when model-rating a prototype Cut-throat flume.
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