Among the climatic factors that interfere in water erosion, precipitation, expressed by the rainfall erosivity, is of great importance. Therefore, its knowledge becomes fundamental for the recommendation for soil management and conservation practices that seek the reduction of water erosion. In that context, the objectives of this work were: a) to determine the rainfall erosivity and its distribution at Rio Doce Valley, Minas Gerais State, for nine sub-regions, b) to estimate the monthly EI30 index in the period from 1969 to 2005 for Ferros and Guanhães counties, and c) to determine the return periods of the monthly and yearly erosivity indexes. The average erosivity value obtained was 12.913 MJ mm ha-1 h-1 year-1, being classified as very high. Among the sub-regions, the erosivity values varied from 8.243 to 26.676 MJ mm ha-1 h-1 year-1. The critical periods in relation to water erosion due to the occurrence of erosive rains are January-March and November-December, contributing with 88.6% of the annual erosivity. From April to October, the occurrence of critical erosivity practically does not exist. The estimated individual maximum values for the return periods of 1, 10, 50, and 150 years were of 5.508, 15.534, 18.110, 19.632, and 5.542, 17.653, 20.954, 22.931 MJ mm ha-1 h-1 year¹ for Ferros and Guanhães, respectively. The determination of the erosivity values throughout the year allows to identify the months in which the risks of soil and water losses are higher, which is important for planning the conservation practices.
Erosivity; conservation planning; rainfall coefficient; rainfall return period
