An instrumental method for sedimentation rate determination, using 210Pb natural radioactivity and the Constant Rate of Supply (CRS) model, is presented for the Santander Bay, Spain. Two sampling points were analyzed, one is affected industrially, and at the other, the industrial impact has been minimal. The results indicate a growth of the sedimentation rate in the two points studied, in the first point from 0.06 cm·y–1 to 0.35 cm·y–1, approximately from the beginning of the 20th century until the present time.The interrelation between the periods of maximum industrialization and the maximum variations in the sedimentation rate was investigated.