ERDC/CHL CHETN-III-70
July 2005
Calculate wave momentum flux parameter: First calculate values of relative wave height and
relative depth as
H
h
8 ft
20 ft
=
= 0.4
=
= 0.0077
and
2
2
2
h 20 ft
gT
(32.2 ft / sec )(9 sec)
Next, find the values of the coefficient A0 and A1 from Equations 7 and 8, respectively, i.e.,
2.026
⎛H⎞
A0 = 0.639 ⎜ ⎟
= 0.639 (0.4)2.026 = 0.0998
⎝h⎠
-0.391
⎛H⎞
= 0.180 (0.4)-0.391 = 0.2576
A1 = 0.180 ⎜ ⎟
⎝h⎠
Finally, the nondimensional wave momentum flux parameter is calculated from Equation 6 as
- A1
⎛ MF ⎞
⎛ h ⎞
= 0.0998 (0.0077)-0.2576 = 0.35
= A0 ⎜ 2 ⎟
⎜
2⎟
⎝ ρgh ⎠max
⎝ gT ⎠
Calculate runup for 1:2 slope:
For rubble-armored impermeable slopes, the appropriate runup equation for both surging/collapsing
and plunging/spilling breaker types is given by Equation 13 as
1/ 2
0.7 ⎛ M
⎞
Ru 2%
= 4.4 ( tan α ) ⎜ F2 ⎟
(0.505)
⎝ ρgh ⎠
h
First check that the structure slope falls within the range of applicability for Equation 13, i.e.,
1
1
cot α =
=
= 2.0
tan α 0.5
which is within the range of 2.0 ≤ cot α ≤ 4.0.
The nondimensional relative 2-percent runup is found as:
1/ 2
0.7 ⎛ M
⎞
Ru 2%
= 4.4 ( tan α ) ⎜ F2 ⎟
(0.505) = 4.4 (0.5)0.7 (0.35)1/ 2 (0.505) = 0.81
⎝ ρgh ⎠
h
and the dimensional 2-percent runup is
Ru 2% = 0.81 h = 0.81 (20 ft) = 16.2 ft
9
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