New approach for obtaining the C-factor of RUSLE considering the seasonal effect of rainfalls on vegetation cover

We present a new approach for calculating the C-factor of RUSLE considering the effect of low-reflectance vegetation cover areas on the reduction of the effects on erosion caused by rainfall seasonality. For this, we propose the coefficients Cr2 (rescaled 2) and C-PC (Precipitation Correction), which represent the C-factor, and an adaptation in NDVI calculation, according to the seasonality of precipitation (NDVI-PC). The Cr2 factor is used when there is no seasonal effect of rainfall on vegetation, while the C-PC factor is calculated for localities under the influence of seasonality, from NDVI-PC. The proposed approaches were tested using different satellites images in the Palmares-Ribeirao do Saco watershed, Rio de Janeiro, Brazil. The values of Cr2 and C-PC factors were compared to the Cr factor (rescaled) and to mean values from the literature for different land covers. Our results indicated that the Cr2 factor represents an improvement in accuracy in relation to Cr by considering specific values of the studied area to normalize the data without generalizations. Furthermore, the C-PC factor is able to simulate the effect of seasonality, providing more realistics values of soil loss by the RUSLE as a function of the proportion of area affected by the rainfall seasonality obtained from NDVI-PC. We conclude that both Cr2 and C-PC factors generate values similar of the C-factor observed in the literature, and therefore are able to provide better soil loss estimation than that using the Cr factor.