Journal of Geophysical Research vol:111 issue:D22109 pages:1-11
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 ha(-1) h(-1) yr(-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 annual R 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 of muddy 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 decade of 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.