This paper puts forward a mathematical model to estimate the sediment concentration in natural streams of a subriver basin of the Eighth Region of Chile. It is proposed as a result of the intensive handling of forest plantations, mainly of Pinus radiata (D. Don). The study site is the river basin of the Vergara River, with a surface area of 385.300 ha. The variables used in the model were average monthly precipitation, discharge, trucks flow and ways length. The analysis indicated that the trucks flow and ways length did not cause an immediate impact on sediment production. A phase angle of five and six months was observed for the trucks flow and ways length, respectively. The model, calibrated with the variables already indicated, allowed us to determine the correlation coefficient (R2 ) of sediment production as 0.90, with 99% of confidence.