Structure Height
Waves breaking against an inclined structure will run up to an elevation higher than the Stillwater
level depending on the roughness of the structure. Smooth concrete surfaces experience higher runup
than rough stone slopes. Vertical structures also cause splashing and can experience overtopping. If
possible, the structure should be built high enough to preclude severe overtopping. White spray does
little damage, but solid jets of "green" water should be avoided. The required height of the structure will
depend on the computed runup height based on the wave and structure characteristics. Detailed guidance
is presented in Stoa (1978) and (1979). The runup height, R, can be found by a more approximate
method as given below.
First, find the wavelength at the structure by using either Figure 26 or Equation (3) with the known
depth at the structure and the design wave period. The definition sketch for runup is shown on Figure 27.
For SMOOTH impermeable slopes, the runup, R, is given in Seelig (1980) by,
R=HC1 (0.12L/H)^(C2 (H/ds)0.5 + C3)
where:
L=
the local wavelength from Figure 26 or Eq. (3),
ds =
the depth at the structure (feet),
the approaching wave height (feet), and
C1, C2, C3
= coefficients given below.
Structure Slope *
C1
C2
C3
Vertical
0.96
0.23
+0.06
1 on 1.0
1.47
0.35
-0.11
1 on 1.5
1.99
0.50
-0.19
1 on 2.25
1.81
0.47
-0.08
1 on 3.0
1.37
0.51
+0.04
*
Interpolate linearly between these values for other slopes.
For ROUGH slopes, Seelig (1980) gives the runup as,
R = (0.69ξ/1+0.5ξ)H
(14)
ξ = tan θ/(H/Lo)0.5
(15)
Lo = 5.12 T2
(16)
θ = structure of the slope (e. g., tan θ = 0.25 for a slope of 1V on 4H
55
Previous Page
