The modified Parker bedload equation incorporates the method of critical stress calculation of Shvidchenko (2000). The general form of the modified equation is the same as the original one:
where
and the normalized dimensionless bed shear stress 
is defied as
where
and 
is the reference stress corresponding to a small reference transport rate 
, which is related to the Shvidchenko’s (2000) critical stress as
The value of critical stress 
is defined as:
a is the particle mobility factor,
b is the mixture mobility factor,
is the mixture geometric standard deviation (for bed surface):
is the hiding function,
and e is the hiding parameter,
The suggested applicability of the modified Parker equation is for uniform/graded coarse sand and gravel.