Wave Response of Port Allen Harbor, Kauai, Hawaii.

Abstract : Port Allen Harbor, located on the southern coast of the island of Kauai, is protected from the open ocean by a single nibble-mound breakwater. Severe tropical storms in past years have damaged this structure, reducing the most seaward 66 ft of breakwater length to a submerged mound. To evaluate the impact of the shortened breakwater on harbor protection, primarily against wind waves and swell, the HARBD model was employed using incident wave conditions with periods between 6 sec and 20 sec. Approach directions ranged from 112.5 deg to 239.5 deg, the full range of directions seen by the harbor. A high-resolution finite element grid (38,000 elements) was generated with new automated software. The HARBD model produced wave amplification factors for 20 locations throughout the harbor basin. Following runs representing both the original and shortened breakwater lengths, these factors were evaluated using both recently developed visualization software and new interpretation methods. This approach allowed quantitative conclusions about the benefits of restoring the damaged breakwater back to its original length. The study indicates that a small measure of extra protection is provided by the original breakwater length relative to the existing condition. The extra protection would reduce wave heights by a maximum of 5 percent. Finite element, Kauai, Wave refraction, Harbor, Numerical modeling, Wave response, Hawaii, Port Allen.