The stage-discharge relationship or rating curve at a river cross-section is a fundamental technique in hydrology employed for determining discharge from catchments. While river cross-sections are inherently variable, it generally takes quite some time for a change in cross-section to occur. Thus, where good quality of data on stage and discharge quality are available, a stable and representative rating curve may be established. However, all too often, the natural variability is aggravated by data errors of human origin.