**4. Rainfall simulators: Performance and calibration**

The characteristics of simulated rainfall are reliant on the type of nozzle employed, the water pressure exerted, and the arrangement and movement pattern of the

nozzles through the rotating bar (nozzle boom) [24]. Therefore, the performance of any rainfall simulator must be evaluated for the ability to produce different rainfall intensities (rainfall intensity calibration), the spatial uniformity of the simulated rainfall over the flume area, the rain Drop Size Distribution (DSD), the terminal velocity, and kinetic energy of simulated rainfall events.
