How appropriate is the alternating block method to represent flooding from extreme precipitation events?

Running inundation on a stochastic event set with thousands of events can be quite time consuming, especially if physically based methods such as the shallow water equations are used. In order to optimize runtime and to keep a high spatial resolution, event footprints are often reconstructed using return period maps. However, this means that design storm events need to be constructed for each return period which should ideally be representative for different event durations.

Here, we compare the alternating block method, a popular design storm model, to actual event hyetographs from a selection of storm events in Florida. The hyetographs are input to a 10m grid-based Green-and-Ampt infiltration model which is coupled to a two-dimensional shallow-water inundation model. The difference between the alternating block method and the actual event hyetograph is measured based on the flood extent and depth.