Cress Help - Wind waves and swell - Wave / structure interaction - wave transmission - Z17.2

Transmission over low breakwater

In this rule wave transmission is calculated according to :

Van der Meer
Hamer & Hamer
Powel
Goda & Seelig

For all equations the following applies:

F = Freeboard, crest of dam above SWL (in case of submerged dam, F is negative)
b = crest width
n = slope of dam []
For a vertical wall use n=0 (only applicable to the Goda formula)
h = water depth
T = incident wave period
The ratio b/L should be more than 0.2, otherwise the Ht-value is higher than calculated. Only Goda, for vertical walls gives also a correct value for small crests.
The average error in the value Ht/Hi is on the order of 0.2 in all formula.

Method of Van der Meer

Only valid in case –2 < F/HI < 2

The standard deviation of the observations used for fitting the curve is = 0.09, and p follows from the Gauss distribution (for 10% exceedence use p=1.24)

Method of Hamer & Hamer

Method only valid for non-submerged dams (thus F>0) and slopes more gentle than 1:1

In case the equation yields a negative value for Kt, then Kt = 0

Method of Powel

First Run-up is calculated with the Old Delft Formula:

The method is only valid for:

-slopes more gentle than 1:1

Method of Goda and Seelig

The method is only valid for slopes more gentle than 1:0.7 (1.4:1 or 55 degrees)

For a slope use

For vertical wall, first calculate:

The transmission coefficient is given by:

 

References:
Seelig; proc. coastal structures 1979
Hamer&Hamer; Coastal Engineering 6-1982
V.d.Meer; see Manual on Rock in Coastal Eng. pp 256-259
For Goda see Shore protection manual
The reliability of van der Meer's formulae was described by considering the transmission coefficient Kt as a normally distributed stochastic variable with a standard deviation of 0.09
For further information, one should refer to Manual on Rock in Coastal Eng. pp 256-259