The correlation between the erosivity index EI30 and the rainfall coefficient (Rc) for the period of 1962 to 1981, in Fortaleza (CE), was evaluated to analyze the feasibility of the Rc use to update erosivity values from 1982 to 2000 in this county. An equation that could be used to estimate erosivity in other locations of the coastal region of Ceará State, where there are no rain gauge charts available, was a second aim. A high correlation coefficient (r = 0,99**) was found between the monthly EI30 index and the Rc values. The best fit in the regression between these variables was found in the equation EI30 = 73,989Rc0,7387. The use of this equation allowed to update the R factor in Fortaleza between 1962 and 2000, thus extending the coverage of erosivity data to an uninterrupted series of 39 years. The updated R factor for this series was 6.900 MJ mm (ha h y)-1, and 69,5 % of this annual value was distributed in the months of January to April. This study also provides useful information for erosion control planning and to estimate erosivity, where no rain gauge charts are available, with reasonable accuracy for other locations within the coastal region of Ceará.
Index EI30; rainfall coefficient; R factor; Universal Soil Loss Equation
