where:

=

4.780 in SI units

Ku1

Ku1

=

1.606 in English units

=

10.846 in SI units

Ku2

=

3.306 in English units

Ku2

qB

=

Metric-tons/day/meter (Tons/day/foot)

Water discharge quantity determining the bed-load transport, m3/s (cfs)

=

Qb

Total water discharge m3/s (cfs)

Q

=

D90, Dm

=

In millimeters (both SI and English units)

The quantity Dm is the effective diameter of the sediment given by

ΣipiDsi

Dm =

(4.20)

100

where:

=

Percentage by weight of that fraction of the bed material with geometric

pi

mean size, Dsi

The term nb is the Manning's roughness coefficient for the bed of rectangular channels

2/3

n w 3 / 2

2y

1 -

nb = n1 + o

(4.21)

n

W

and for trapezoidal channels

2y (1+ H2 )1/ 2

2/3

nw 3 / 2

nb = n1+ o

1-

(4.22)

s

W

n

where:

n, nb, nw

=

Roughness coefficients of the total stream, of the bed, and of the

banks, respectively

=

Horizontal side slope related to one unit vertically

Hs

W

=

Bottom width

The ratio Qb/Q for rectangular channels is given by

Qb

1

=

(4.23)

3/2

Q

n w

2y

1+ o

W

nb

4.12

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