Cress Help - Wind waves and swell - Waves near the shore -Shoaling waters - Wave breaking - z12.1

Calculation of breakerdepth and refraction

Short description
This rule calculates the changes of linear waves near coasts with parallel depth contours

Used equations
Deep-water wavelength and shallow water wavelength are calculated with the standard approximations used by Cress (see rule z10: orbital movement)

The shoaling coefficient can be calculated directly:

    equation 1

he direction of the wave is given by:

    equation 2

The refraction coefficient is given by:

    equation 3

The wave height at breaking is:

    equation 4

Additionally breaking takes place at the point where

    equation 5

An iteration procedure starts at a depth of 3 times H0 and moves towards the coastline. As soon as the breaker-criterion is met, iteration stops. The breaker index (sometimes called breaker parameter) is used as input. For single (solitary) waves one should use a value of 0.78 For random waves (calculation on the basis of Hs) one should use a value of 0.4 to 0.5. For steep slopes one may use 0.6 Kamphuis suggests in his book to use:

    equation 6

in which m is the beach slope. This gives the following values for the breakerindex:

beach slope breaker index
1:10  0.79
1:25  0.64
1:50  0.60
1:100  0.58
1:500 and less  0.56

references:
Kamphuis, J.W. [2000] Introduction to coastal engineering and management. Advances Deries on Ocean Engineering, vol 16, World Scientific, Singapore, ISBN 981-02-3830-4 or 981-02-4417-7 (pbk)