Berm for Reducing Wave Overtopping at Commercial Port Road, Guam

This paper describes the procedures and results of a typhoon overtopping-frequency analysis for a vulnerable section of the commercial port road along Cabras Island, Apra Harbor, U.S. Territory of Guam. The study was a challenging application of present numerical modeling technology to an innovative project design. INTRODUCTION Apra Harbor, Guam's commercial port, is located on the west side of the island. The harbor is well-protected by a combination of natural features and Glass Breakwater, a long man-made breakwater connecting into Cabras Island on the shoreward end (Figure 1). Cabras Island is a narrow, east-west oriented island which not only affords protection to the harbor, but also accommodates many of the cornmereial port facilities. The port access road runs along the north side of Cabras Island. The container yard occupies most of the west-central part of Cabras Island. In this area, the road is protected from the sea by a relatively low, recurved concrete seawall fronted by a rubble-strewn beach. Subaerial beach width ranges from 30 m (100 fl) to 70 m (230 fl) along the vulnerable area. A coral reef extends seaward a distance of about 100 m (300 fl). During storms, waves can run up the beach, overtop the seawall, and cause disruption and damage to the road and port facilities. The U.S. Army Honolulu Engineer District (HED) and U.S. Army Corps of Engineers, Pacific Ocean Division, have developed a project design to reduce vulnerability of the road and container yard to overtopping and flooding (POD 1995). I Hydraulic Engineer, U.S. Army Engineer Res. & Dev. Center, Coastal & Hydraulics Lab., 3909 Halls Ferry Road, Vicksburg, MS 39180-6199 USA. Edward.F.Thompson@erde.usaee.army.mil 2 Hydraulic Engineer, U.S. Army Engineer Dist., Japan; formerly with Honolulu Engineer Dist., U.S. Army Corps of Engr., Honolulu, HI 96858-5440 USA. Lineoln.C.Gayagas@poj02.usaee.army.mil