Riprap Size for a Given Velocity and Depth
(RS-Record) Calculations
Input and Output
The input window for these calculations is accessed from the SAMwin main
menu Edit Hydraulic Function Input Riprap size, Known Velocity and
Depth, Figure 6.10.
Figure 6.10. Finding the Riprap Calculations input screen.
When flow velocity and depth are known, the riprap size is calculated using
the equation described in EM 1110-2-1601 (USACE 1991, 1994). Since the size
and specific gravity of available riprap are needed for this calculation, the 13
standard riprap sizes (shown in EM 1110-2-1601 and in Chapter 2) are available
in the program by default. The riprap design equation is:
2.5
γ
0.5
V AVE C B
d 30 = S f C S CV CT D
w
γ -γ
s w
K1 g D
where
d30 = characteristic riprap size of which 30 percent is finer by weight
Sf = Safety factor
CS = Coefficient of incipient failure
CV = vertical velocity coefficient
CT = coefficient for riprap thickness
D = local water depth
γw = unit weight of water
γs = unit weight of riprap
VAVE = average channel velocity
CB = bend correction for average velocity (VSS/VAVE)
K1 = Correction for side slope steepness
g = Acceleration of gravity
100
Chapter 6
Input Requirements and Program Output for SAM.hyd
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