SENSITIVITY OF ESTIMATES FOR THE DESIGN FLOOD MAGNITUDE TO HYDROLOGIC AND STATISTICAL APPROACHES

Abstract: Operational comparisons are presented to estimate the design flood magnitudes with a specified return period, resulting from use of statistical and hydrological approaches. For the statistical representation of flood peaks, several probability distributions are used to describe the annual maximum series. For the hydrologic representation of flood peaks, the storage-routing model is newly developed, which can be applied to the rainfall-runoff processes in subbasins as well as flood propagations in channels. The proposed model makes the runoff and channel routing procedures considerably useful than a kinematic routing, yet maintains the same physical and hydraulic characteristics and saves much computer time and effort even for large river basins. Estimates of the 100-year design event and their standard errors were compared between the observed and computed annual maximum flows fitted by the three-p arameter distribution models in the Yubetsu River basin, Hokkaido, Japan