Simons et al. (1981) basic power function method
Kodoatie et al. (1999) expanded power function method
Yang (1996) sand and gravel equations
A summary of each method is given below to aid in selecting which method to use.
Meyer-Peter and Mller Bed Load Equation
The Meyer-Peter and Mller bed load equation only calculates the bed material moving in
contact with the bed (contact load). It does not give total bed-material discharge unless there
is no bed-material in suspension. It is, therefore, best utilized for coarser bed material
streams (D50 coarser than 2.00 mm).
Colby's Curves and Method
Colby's method is only for sand size bed material (D50 from 0.6 to 2.00 mm). It is very good
method for rapid determination of total bed-material discharge. It can be used to check or
compare with the other methods. The method can be used to determine the total bed-
material transport by size fraction.
Simons et al. (1981) Power Function Relationship
The Simons et al. power relationship can be used for steep streams with sand and fine
gravel-size bed material (D50 from 0.1 to 5.0 mm) that normally exhibit critical or supercritical
flow. The relationship takes into consideration the size distribution of the bed material (Table
4.2). The difficulty in the method is the need to interpolate between sand sizes and gradation
Kodoatie et al. (1999) Power Function Relationship
The Kodoatie method (modified Posada (1995)) can be used for streams with bed material
size ranging from silt to gravel. It provides a coefficient and exponents based on classifying
streams as silt, fine sand, medium to coarse sand and gravel bed (Table 4.4). The method is
useful for rapid calculations of bed-material discharge.
Yang (1996) Sand and Gravel Equations
The Yang equations can be used for sand and gravel total load estimation. The equations
can be applied by size fraction or to the median size. The gravel equation should be limited
to median sizes between 2.0 and 10.0 mm.
The use of computer models is beyond the scope of this manual, but programs are available.
Two of the better known computer models are:
BRI-STARS (Molinas 2000)
HEC-6 (U.S. Army Corps of Engineers 1993)
These computer models have the ability for user-selected sediment transport relations
(including most of those shown in Table 4.1 see Section 4.6) and power relationships. The
models can be used to determine the total sediment discharge for a given flow or to