Rain Events – Euler type II

The Euler type II method is widely used in Central Europe for generating synthetic design storms. Like the Chicago Design Storm, it is based on Intensity–Duration–Frequency (IDF) curves that describe the relationship between rainfall intensity, storm duration, and return period.

In the Euler type II method, the total rainfall depth for a given duration and return period is distributed across the event in fixed time steps according to a predefined profile:

1. The Sherman equation is used to compute cumulative rainfall depths for each time step.
2. The increments between successive steps are calculated and ranked by size.
3. The peak intensity occurs at a peak-time ratio of 0.3, meaning 30% into the event.
4. The next largest increments fill the period before the peak, and the remaining increments are assigned after the peak.
5. The resulting hyetograph is scaled to ensure that the total rainfall depth matches the analytical IDF curve.

This results in a strongly front-loaded storm profile.