We could characterize a suspension of flocs based on the terminal velocity of the flocs and on the turbidity of the narrow ranges of particle size. Since the particle size will be measured in terminal velocity, the narrow ranges of particle size will also have dimensions of velocity. Thus the y axis will have units of NTU/(m/s). The x axis has units of m/s, and the area under the curve is thus the total turbidity of the suspension. A suspension with a small number of very small particles and a large number of large particles is shown in the figure.