Özet:

Soil erosion is one of the major threats to the conservation of soil and water resources in the semi-arid and arid regions of Turkey. Therefore, there is a need to accurately assess soil erosion and accordingly determine the specific control activities adaptable to these conditions. Using the daily rainfall amounts recorded from 1958 to 2003 from 11 climate stations by the Turkish Meteorological Service in the semi-arid area of Beypazari, Ankara, Turkey, 5 different procedures of calculating the Modified Fournier Index (MFI) were performed to obtain the effect of rainfall variability and incidence of extreme storms on assessing 'Actual Soil Erosion Risk' (ASER) by CORINE methodology. MFI surface calculated from the averages of ith monthly rainfall amounts and averaged over a number of years (MFI) caused ASER to underestimate the soil erosion since it was statistically unable to account for the year-to-year variations in the rainfall data. In addition to within-year variations, introducing the year-to-year variations to MFI surface, which was estimated from the monthly rainfall amounts of each individual year and averaged over a number of years (MFIj-) to some extent refined ASER surface. However, ASER surfaces produced by the monthly return frequencies of rainfall events for 10 (MFI10), 20 (MFI20), and 30 (MFI30) years showed significant improvements and agreements with the erosion classes of the conventional soil survey of the study area.

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