Toffaleti (1968) developed a total-load transport formula primarily for sand particles. The method splits the water column into three vertical zones as shown in the figure below.
Figure 2 20. Toffaleti total-load transport zones.
The formula computes the concentration in each of the three zones using a Rouse concentration profile. The suspended-load transport potential for each zone is computed analytically assuming a current velocity profile. The total-load transport potential is computed as the sum of the three suspended-load zones and the bed-load zone. The sediment transport potential formulas are not based on excess shear but rather are regression equations based on sediment and water properties, and hydraulic variables. The Toffalti formula was originally developed for bulk transport but here it is applied to individual grain classes. The Toffaleti formula is usually applied at "large" rivers since most of the data used to develop it were from large suspended-load dominant rivers. The Toffaleti bed-load transport potential does not perform for gravel size or coarse particles. For this reason, the option is available to replace the bed-load transport potential in the Toffaleti formula with an estimate from the Meyer-Peter and Muller formula. This formula is referred to as the Toffaleti-MPM formula.