Impermeable dam

   General introduction

The calculation rule computes the wave transmission of the significant wave over/through a "reef" breakwater, a conventional breakwater, a highly permeable breakwater, a vertical breakwater, an impermeable dam, vegetation or a row of piles. A "reef"-breakwater consists of a homogeneous pile of stones and has a low crest. A conventional breakwater is a layered structure (fine grading in the core overlain by several layers of coarse stone). In practice, a highly permeable breakwater will permit water only to pass though the structure and not over the top (no overtopping). A vertical breakwater consists of a caisson on a permeable foundation of stones. Transmission occurs as a result of overtopping, wave penetration under the caisson and movements of the caisson. Wave transmission through vegetation can be determined for rushes (scirpus sp./ scirpus lacustris) and for reeds, if the stalks extend above the surface of the water. With impermeable dams wave transmission occurs only via overtopping. Finally transmission through a row of piles depends on the distance between the piles, the size of the splits between the piles and the shape of the piles (round or square).

In general:

     (equation 1)

   Impermeable dam

              (equation 2)

During the implementation the following must be mentioned: 
"this equation has been verified for a slope of 1:3.5, a crest width of 0.2 m and a wave steepness of (Hs/L0p) van 0.02 - 0.04".

Where:

• Hs = width of planting, measured in the direction of the wave progression [m]