Uncertainty Analysis of Roughness Measurements for a Large-Scale Canal

Abstract: Factors related to the uncertainty of roughness measurements were analyzed in a large-scale canal: the Middle Route Project (MRP) in China. With field observation data of seven canal sections, a formula to estimate the uncertainties of the roughness coefficients was derived, and sensitivity coefficients were determined. Curves illustrating the variations of the sensitivity coefficients and roughness coefficient uncertainties with spaces between water level stations are presented. Exponential fitting formulas were generated. In this study, it was shown that the flow rate measurements were the main source of error and dominated the calculation of the uncertainty. The uncertainty can be reduced by increasing the space between water level stations. This is especially effective within a specific spacing range, which can be identified from the fitting formulas.

Key Words: Roughness; uncertainty analysis; canal; sensitivity coefficient