1ST-ORDER ANALYSIS OF OPEN-CHANNEL FLOW

The effects of uncertainty in Manning's roughness coefficient and the empirical nature of Manning's equation on return period of flood stages have been analyzed using first-order reliability methods (FORM). This method generally used for structural reliability was applied to hydraulics by using Manning's equation as the basis for a limit state function. This paper also describes a way to compare the FORM results, a safety index, to the results of the traditional frequency method, a probability, by changing both to a return period. © ASCE.