CMS-Wave:Transmission

Wave Transmission over structures

(Summarized from from JCR SI 59 pp7-14)
Wave transmission is exhibited by fall of the overtopping water mass. The ratio of structure crest elevation to incident wave height is a key parameter governing the wave transmission.

Note: The term used in the Surface-water modeling system for these structures will be colored red, inside parentheses with bold and underline to make it easier for users to find the appropriate term. For example, (Rubble Mound)

Impermeable Structures

Low-crested or submerged impermeable structures (Rubble Mound)

CMS-Wave calculates the transmission coefficient $K_{t}$, defined as the transmitted wave height divided by the incident wave height, based on the simple expression (Goda, 2000):

$K_{t}=0.3\left(1.5-{\frac {h_{c}}{H_{i}}}\right){\text{, for }}0\leq {\frac {h_{c}}{H_{i}}}\leq 1.25$

(Eq. 10)

Composite breakwater protected by a mound of armor units at its front (Wall Breakwater)

$K_{t}$ is calculated as

$K_{t}=0.3\left(1.1-{\frac {h_{c}}{H_{i}}}\right){\text{, for }}0\leq {\frac {h_{c}}{H_{i}}}\leq 0.75$

(Eq. 11)

where:
$h_{c}$ is the crest elevation of the breakwater above the still water level
$H_{i}$ is the incident wave height.

Permeable Structures

For permeable structures, wave transmission is calculated using modifications to d'Angremond et al (1996) formula.

Semi-Permeable rubble-mound breakwaters (Semi-permeable)

$K_{t}$ is calculated using as:

$K_{t}=0.64\left[1-\exp \ \left(-{\frac {\xi }{2}}\right)\right]\left({\frac {B}{H_{i}}}\right)^{-0.31}-0.4{\frac {h_{c}}{H_{i}}}{\text{, for }}\mathrm {B} <10H_{i}$

(Eq. 12)

The remaining permeable structures effectively use a factor to increase transmission.

Highly permeable [for piers or docks] (Highly permeable)

Approximately $K_{t}$ from Eq. 12 increased by 25% (factor of 1.25)

Floating breakwater (Floating breakwater)

Approximately $K_{t}$ from Eq. 12 increased by 50% (factor of 1.50)