Document Type : Research Paper


Tarbiat Modares University


Regarding the undeniable role of rainfall erositivity factor in initiating water erosion, studying its different aspects is important in optimal soil and water resources management. It is taken in to account in many soil erosion estimation models which are used for soil and water conservation. However, the impact of data length, study span, and the number of stations on variability of rainfall erosivity factor has been understudied. The present study therefore is an attempt to investigate the temporal variation of Wischmeier and Smith’s rainfall erosivity factor at different time scales and also the effect of data length, study span, and number of stations upon rainfall erosivity factor is scrutinized. Accordingly, the results of the present study with 70 stations, data span of 20 years and different study periods were compared with those obtained for another study with 18 stations and 23 years of data span. Rainfall erosivity factor of over 12,000 storm events was calculated in present study and mean values for different time scales were compared using t-Test. Results showed that the maximum and the minimum values of monthly rainfall erosivity factor in the country were different from each other. Besides, the results of t-Test showed significant difference between the calculated values of rainfall erosivity factor in some months (p<0.05) and seasons (p<0.05). Nonetheless, the difference between annual rainfall erosivity factor was not significant (p<0.05).


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