Estimating Probabilities of Extreme Rainfalls

For a variety of design purposes there is increasing interest in estimating probabilities of rare floods, with magnitudes up to the probable maximum flood. One estimation approach, which we term “stochastic storm transposition,” is a generalization of the concept of storm transposition, which is the basis for estimating probable maximum precipitation. We explore the concept of stochastic storm transposition, and demonstrate the application of two alternative formulations of this concept to a catchment in the midwestern United States. It is clear from these applications that before the concept can be applied routinely its theoretical basis must be strengthened and several potentially large sources of uncertainty must be explored.