Error analysis of roughness coefficient calibration for channels
This paper studies the relationships between the error of the channel roughness coefficient cali- bration and that of the hydraulic measurement. According to the principle of hydraulics, the formula of de- termining the error of the channel roughness coefficient calibration is deduced explicitly. Based upon the measured data from the Beijing-Shijiazhuang Emergency Water Supply Project of South-to-North Water Di- version, the error analysis of the roughness coefficient calibration is carried out for the typical channels. Some important conclusions are attained: (1) tiny hydraulic measurement error may result in significant er- ror of the channel roughness coefficient calibration and for the existing typical channel the error can reach 11%; (2) the relative error of the roughness coefficient caused by the volumetric discharge is approximatly equal to the error of flow meter; (3) if the measurement errors of the water depths are the same, the er- ror of the channel roughness coefficient calibration caused by the inlet water depth is very close to that caused by the outlet water depth. When the channel length is short, the error of the channel roughness co- efficient calibration will increase significantly.