Investigating rainfall erosivity indices in arid and semiaridclimates of Iran

Abstract: The rainfall erosivity index is one of the most important factors influencing soil erosion. For this reason,investigating the accuracy of rainfall erosivity indices is very important in different climatic regions. The objective of this research was to investigate different rainfall erosivity factors and determine the most appropriate ones for use in the central and northeastern parts of Iran. For this reason, necessary data were collected from 92, 6 and 10 soil erosion research plots in Khorasan Razavi, Semnan and Isfahan provinces, respectively. The rainfall intensities were recorded, as was the sediment yield associated with storm events, and 63 different erosivity indices based on rainfall intensity were computedfor these soil erosion research stations. The results demonstrated that the √P X I²30, √P X I²60, and (P X T)²/ √d rainfall intensity-based indices had the most significant correlations, with results of 0.740 (P 0.01), 0.651 (P 0.01) and 0.976 (P 0.01) for sediment yield in Khorasan Razavi, Semnan, and Isfahan, respectively. These selected rainfall intensity-based indices were also computed for synoptic stations. Rainfall erosivity indices, based on the amount of rainfall, were also computed for all soil erosion research plots and synoptic and climatic stations. The results showed that mean annual rainfall displayed a significant correlation with selected rainfall intensity-based indices (r = 0.83 and 0.99, P 0.01) in the synoptic stations of Semnan and Khorasan Razavi, and the modified Fournier index showed a significant correlation with selected rainfall intensity-based indices (r = 0.90, P 0.01) in Isfahan. Selected regression models wereused to estimate the rainfall intensity-based indices at stations without intensity data in the studied provinces.