Peak Discharge Estimation Using Analytical Probabilistic and Design Storm Approaches

The recently developed analytical probabilistic approach was used for estimation of peak discharge rates in a practical design case. The results were compared with those from the commonly used design storm approach. Differences in meteorological data analysis and representation of rainfall input, subcatchment aggregation, and the treatment of the catchment time of concentration between the two approaches were identified as the three main causes contributing to the discrepancy in peak discharge estimates. In spite of the differences, peak discharge estimates from the two approaches are generally comparable for the actual design case. Furthermore, this study revealed that discrepancies caused by subcatchment aggregation and the difference in meteorological data analysis are approximately the same. Treating the time of concentration as a constant across storms of various magnitudes was found not to contribute to a large discrepancy. However, it was shown that the closer the time of concentration values used in the two approaches, the closer the resultant peak discharge estimates.