Wave Transformation and Load Reduction Using a Small Tandem Reef Breakwater – Physical Model Tests

by Andrew Cornett, NRC Coastal Engineering Program, Ottawa, Canada,
Etienne Mansard, NRC Coastal Engineering Program, Ottawa, Canada,
Edgar Funke, NRC Coastal Engineering Program, Ottawa, Canada,

Document Type: Proceeding Paper

Part of: Ocean Wave Measurement and Analysis


The performance of several small reef breakwaters, and a tandem breakwater system (consisting of a reef breakwater positioned upwave from a surface-piercing main breakwater), are quantified through a limited set of physical model tests. Wave reflection and transmission coefficients for the reef breakwaters are computed from wave probe measurements in irregular waves. The character, and wave height distribution, of waves transmitted past the reef breakwaters are also examined. Fluid forces acting on the armour stones of the main breakwater are measured using a force panel, and compared to the characteristics of waves transmitted past the reef breakwaters, and to observations of armour stone damage. Reductions to extreme wave heights and extreme loading events, induced by several different reef breakwaters, are quantified and favourably correlated to improved armour stone stability. These results demonstrate the successful performance of a tandem breakwater system incorporating a relatively small, low-crested reef breakwater. Extrapolation and generalization of these results to different tandem breakwater systems and wave conditions will require further model testing.

Subject Headings: Breakwaters | Coastal protection structures | Load tests | Reefs and sills | Wave reflection | Water waves | Load factors | Physical models

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