The main goal of this study is to better understand the relationships between rainfall erosivity and sediment yield during 1982 to 2018 in the Shirin Darrehdam (SDD) basin (1750 km2), North Khorasan Province, northeastern Iran. Rainfall erosivity was evaluated by the Fournier index (FI), Modified Fournier index (MFI), and rainfall erosivity (R factor), and specific sediment yield (SSY) was obtained based on the Fournier empirical model (FEM) using daily precipitation data from 3 and 2 gauging stations in the upstream and downstream of the dam, respectively. The relationship between rainfall erosivity, precipitation, and sediment yield was assessed by the coefficient of determination (R2)and Pearson coefficient (r). The results showed that the upstream of the dam was more affected by rainfall and produced more sediments than the downstream. Strong correlations were observed between the sediment yield, precipitation, and rainfall erosivity indices (R2≥0.5 and the correlation was significant at the 0.01 level based on the r2. The primary sources of sediment supply are the easily eroded sedimentary rocks such as the shale (Sanganeh Formation) and marl (Sarcheshmeh Formation) which cover the considerable area in the study basin.

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