Table 6. Graded Riprap Sizes.
Low Turbulence zones, placed in the dry, γs = 165 lbs/cuft
Layer DMAX1
D301 D501 D901
POROSITY2
in
ft
ft
ft
%
No.
1
9
0.37
0.43
0.53
38
2
12
0.48
0.58
0.70
38
3
15
0.61
0.73
0.88
38
4
18
0.73
0.88
1.06
38
5
21
0.85
1.03
1.23
38
6
24
0.97
1.17
1.40
38
7
27
1.10
1.32
1.59
38
8
30
1.22
1.46
1.77
38
9
33
1.34
1.61
1.94
38
10
36
1.46
1.75
2.11
38
11
42
1.70
2.05
2.47
38
12
48
1.95
2.34
2.82
38
13
54
2.19
2.63
3.17
38
Notes:
1
These values were taken from EM 1110-2-1601.
2
These values are estimated from one set of field data.
Riprap Size for a Given Discharge and Cross-Section
Shape
Riprap size is a more complicated calculation when water discharge and cross
section are given than it is when the flow velocity and depth are given because
n-value becomes a function of riprap size. The computational procedure in
SAM.hyd is as follows.
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