Output Reliability as Guide for Selection of Rainfall-Runoff Models

Selection of rainfall-runoff models is dependent on the modeling objectives and the simulation accuracy required. Output reliability is proposed as a measure to help in choosing the appropriate model for a given rainfall-runoff model use. Output reliability can be expressed by the output variable cumulative distribution function, probability density function, confidence limits, standard deviation, or probability of acceptable percent deviation from the predicted value. Approximations of these reliability measures could be established by methods such as first-order second-moment reliability analysis. To demonstrate the approach, an example is given of estimating peak discharge for a watershed in central Illinois using both the HEC-1 and RORB rainfall-runoff models.