D-R-A-F-T
*
u
D
> 30
ν
where
u
=
mean flow velocity
D
=
water depth
ν
=
kinematic viscosity of water
The Manning's shear stress equation
Equation 5
gun
*
u
=
CME D1 6
where
g
=
acceleration due to gravity
n
=
Manning's roughness value
CME
=
coefficient of l.0 for metric units and l.486 for English units
A Jonsson-type equation for surface shear stress
The Jonsson-type equation is for plane beds caused by waves and currents.
Equation 6
f u
1⎛
+ f c u ⎞⎛
⎟ u + uom ⎞
⎜
*
om
u
=
⎜
⎟
w
2⎜
+ u ⎟⎝
u
2 ⎠
⎝
⎠
om
where
ƒw
=
shear stress coefficient for waves
uom
=
maximum orbital velocity of waves
ƒc
=
shear stress coefficient for currents
A Bijker-type equation for total shear stress caused by
waves and currents
Equation 7
1
1
*
u
=
f c u 2 + f w u om
2
2
4
For further information on the shear stress computation equations, see McAnally and
Thomas (1980).
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