v. fine to fine sand-bed
med to very coarse sand-bed
silt-bed
gravel-bed
Figure B.8. Proposed graph by Kodoatie using Equation B.10.
Table B.12. Comparison of Modified Laursen Equations.
Madden
Copeland
Kodoatie et al.
1 Used same equation, but
1 Used same equation,
1 Used same equation but added
modified using Froude No.
modified by 0.018
dimensionless streampower as the
adjustment factor
2 Used modified graph
2 Used modified graph
2 Used modified graph. More specific
in particle size from silt to gravel
3 Used size fraction
3 Used size fraction
3 Used median particle diameter
4 Used Arkansas River data
4 Used both river and
4 Used 33 river systems and 18
flume
data
(not
sources of flume data (total data
specified)
more than 5300 sets)
5 Graph
5 Graph is higher than the original for
is higher than
5 Graph is higher than
sand bed (sand bed is more specific
original for sand bed; not
original for sand bed;
for very fine to fine sand and
specified for gravel and silt
for silt not specified;
medium to very coarse sand);
graph for gravel is
smaller for silt compared to original;
proposed
graph for gravel is proposed
The modified Laursen equation (Kodoatie, 1999) was developed using Group 1 data and
validated using Group 2 data. The following paragraphs show that this modified Laursen
equation provides reasonable estimates of sediment transport for sediment sizes ranging
from silt to gravel bed and rivers ranging in size from small to large.
B.4.3.1 Gravel-Bed Rivers
The relationship between V*/ωi and f(V*/ωi) of data from Group 2 (Meyer-Peter and Mller
laboratory data) for gravel beds is within the range of the relationship between V*/ωi and log
f(V*/ωi) utilizing data from Group 1 (Figure B.9). However, since few field data sets are
reported for gravel-bed rivers, which are usually bimodal, further research should be
conducted in this area. The Meyer-Peter and Mller (MPM) formula may be utilized to check
the results of this analysis. The MPM method is based upon almost 20 years of experimental
work and is probably the most widely utilized relationship for coarse bed material (Simons
and Sentrk 1992).
B.25
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