Long-term (105 years) variability in rain erosivity as derived from 10-min rainfall depth data for Ukkel (Brussels, Belgium): Implications for assessing soil erosion rates Gert Verstraeten, 1Jean Poesen, 1 Gaston Demaree, 2 and Christian Salles 3 Received 6 February 2006; revised 9 June 2006; accepted 31 July 2006; published 29 November 2006.[1] A 10-min rainfall depth time series recorded at Ukkel, Brussels (Belgium) for the period 1898–2002 was used to calculate a long-term rain erosivity record. The rain erosivity factor (R-factor) of the Revised Universal Soil Loss Equation (RUSLE) for the period 1898–2002 equals 871 MJ mm has 1h 1yr 1, based on a newly developed rain intensity–kinetic energy equation (I-KE) for central Belgium. This R-value is 26% larger compared to the R factor based on the I-KE equation recommended in the RUSLE. No significant monotonic trend in annualR-factor could be observed over the entire period, yet a standard normal homogeneity test showed a significantly higher R factor (+31%) for the period 1991–2002 compared to the period 1898–1990. Annual variability in R factor is very high, with a coefficient of variance of 31%. For central Belgium, rain erosivity is highest in the period May–September, which corresponds well with observed soil loss rates and the occurrence omuddy floods. Especially the period May–June is critical with respect to soil erosion. The year-to-year variability in rain erosivity for May–June shows a different temporal pattern than the annual erosivity. No statistically significant increase in rain erosivity for May–June was found, and during the last decadeof the twentieth century these values are lower than average. Despite the lack of a significant trend in annual rain erosivity, average 10-year erosion rates calculated with the RUSLE have increased by 24–34% from 1903–1912 to 1993–2002 for major crops grown in central Belgium, solely as a consequence of changing rain erosivity through time.