Laboratory calibration of open channel bed resistance

This paper deals with the calibration of bed resistance to flow in a straig ht open channel contained within a laboratory flume, The longitudinal slope of the flume was able to be varied, and so the flow could be subcritical o r supercritical. The flow was in the transitional turbulent region, with Re ynolds numbers in the range 3 x 10(4) to 2 x 10(5). The calibration demonst rates experimentally a prediction linking the value of Manning's n with lon gitudinal slope in this region, and indicates a useful approach to define t his relationship. This is of benefit for laboratory work in the smooth or t ransitional turbulent region, particularly if it is wished to employ Mannin g's formula because of its extensive use in river engineering practice.