Calibration of a portable single nozzle rainfall simulator for soil erodibility study in hyrcanian forests

Abstract

A portable rainfall simulator must be calibrated before its application in field experiments. In order to calibrate a portable single nozzle rainfall simulator for a soil erodibility study in Afra Chal site in northern forests of Iran, the following rainfall parameters were assessed; rainfall Intensity-Duration-Frequency (IDF), kinetic energy, drop size and coefficient of uniformity. The results obtained show that for a given return period, the IDF curves decreased with increasing time interval. The velocity of raindrops with an average diameter of 3 mm was 780 cm/s. The simulated rainfall with intensity 32.4 mm/h had kinetic energy at the rate of 25.06 Jm-2mm-1. A rain event with this intensity occurs every 20 years for 20 min in the Afra Chal site and it was randomly selected for calibrating the simulator. Rainfall uniformities that was estimated by the coefficient of uniformity, fell within acceptable limit of 81 to 82%. Key words: Rainfall simulator, drop size, kinetic energy, coefficient of uniformity, intensity-duration-frequency.