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.

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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