Rainfall erosivity in Rondon do Pará, PA, Brazil from 1999 to 2015 and projected to 2035

This study determined the rainfall erosivity value for the urban area of Rondon do Pará in order to provide information about the city's soil loss. The study also determined the probability of erosion occurrence and the return period projected for the next 20 years. The annual distribution of the erosivity index was analyzed and an estimate was made of the correlation between the average monthly erosivity index and the rainfall coefficient. To accomplish this, two types of rainfall data were obtained: 1) data observed by the CMORPH satellites from 1999 to 2015; and 2) data modelled by the RegCM4 model from 2016 to 2035. Erosivity was calculated based upon these monthly and annual rainfall data. Frequency distributions of erosivity values and their return periods were calculated and probability curves were plotted. Regression analyses between precipitation and erosivity were completed. In the period from 1999 to 2015, the value of the R factor of Rondon do Pará was 16,390 MJ mm ha-1h-1ano-1, with a probability of 47% of being equaled or exceeded at least once each 2.1 years. In the period from 2016 to 2015, the R value was 13,038 MJ mm ha-1h-1year-1. Highest soil losses are probable between February and January from 1999 to 2015 and between January and April from 2016 to 2035. The regression mathematical models that had the best results were the potency and the polynomial models for the years from 1999 to 2015 and 2016 to 2035, respectively.