In flash-flood situations, certain portions of the flood hydrograph, such as the rising limb, time to peak, and magnitude of the peak, are more important than others. Typically, for a flash flood, one would expect high values of k and M, and a low Tp value. Hence, these parameters can be used to distinguish flash floods from other flood events within a watershed. For each flood event, parameters k, M and Tp are used to develop relative severity factors RK, RM and RT, respectively, using an ordinal scale of assignment. Thus, the indexing procedure developed in this study provides a systematic way of distinguishing a flash-flood event from other flood events.
Current practice is based primarily on the rainfall event producing flash flooding.
The ability to separate flash floods from other floods based on the characteristics of the observed streamflow hydrograph may provide a better understanding of how to model such events. This in turn can be used to enhance flash-flood forecasting techniques.