The Alii Drive Shore Protection project is located along Alii Drive, in the town of Kailua-Kona, on the western coast of the island of Hawaii. The project was authorized under Section 14 of the Flood Control Act of 1946, as amended and completed in 2000. The County of Hawaii, Department of Public Works (DPW) is the local sponsor and owner of the project, responsible to operate and maintain. The project is in the operations and maintenance phase.
The total project cost was $360,000 (Federal: $234,000; non-Federal: $126,000). The 700-feet long seawall (along Alii Drive) provides stabilization and reduces impacts to the area. During the 1990’s continual wave action against the existing seawall had led to a deterioration of the rock foundation. The DPW has an extensive history of repairs to the existing road pavement and sidewalk, due to the loss of subgrade material. In January 2000, repairs were made to the structure by the U.S. Army Corps of Engineers (USACE) by placing geotextile bags into the voids and then pumping the bags full of concrete. No concrete placement occurred at the Pa O Umi historical landmark or the existing storm drain outlet.
The seawall was damaged by the 11 March 2011 tsunami, originating from the 9.0 magnitude earthquake off the northeast coast of Japan. A series of quake-spawned tsunami waves reached Hawaii about 7 hours after the quake and increased ocean water levels up to 7 feet above tide levels. The waves overtopped the seawall and forced seawater, sand, and other fine-grained material through voids in the seawall that day-lighted on the landward side of the seawall. The sidewalk was uplifted and destroyed, and some uplifting also occurred in patches on the road. While approximately 50 businesses were impacted by flooding, the seawall reduced the overall damages to the area. In accordance with USACE policy PL 84-99, projects constructed under Section 14 are not eligible for repairs.
Alii Drive is the main road of the Kailua-Kona shoreline on the island of Hawai’i. It is the location of many restaurants and shops frequented by tourists and residents.