Design Optimization of a Rubble-Mound Breakwater Using Physical Model Test

In 2023, the Maine Department of Transportation hired Jacobs Engineering Group Inc. to design a fishing harbor in the town of Lubec, located in Johnson Bay, Maine. The project aims to create a tranquil harbor for fishing boats while providing a safe harbor under storm conditions. Prior to preparing physical model testing criteria, four different structural concepts were evaluated based on cost and performance. The chosen concept for the proposed harbor comprises a rubble-mound breakwater structure transitioning into a pile-supported, high-level platform with a wave screen to protect the boats. The detailed design of the composite breakwater structure, due to the unique wave and water level characteristics of the project site, was checked and verified in a three-dimensional hydraulic physical model test. The result of the tests showed that the structure withstood stability and overtopping criteria, and thus could be optimized. Optimization involved reducing the elevation of the structure and reducing the stone size of the rubble-mound portion. This paper presents physical model findings and lessons learned based on model test results.