The Ala Wai watershed encompasses approximately 19 square miles. The Ala Wai Canal is a 2-mile-long man-made waterway constructed in the 1920's to drain extensive wetlands in order to allow development of the Waikiki area on the island of Oahu. The Canal has overtopped and previously flooded Waikiki during both November 1965 and December 1967 storms and during the passage of Hurricane Iniki in 1992. An October 2004 storm flooded Manoa Valley and a March 2005 storm flooded Makiki. The October 2004 storm, estimated to be a 25-year event, caused $85 million in damages including the loss of irreplaceable documents in the University of Hawaii’s library.
Modeling efforts indicate that a 100-year event would result in damages to more than 3,000 structures in the watershed with total damages of about $311 million. In addition, the streams in the Ala Wai Canal serve as the only link between the freshwater ecosystems in the upper watershed and the nearshore marine environment. Both the extent and quality of habitat for endemic aquatic species is impaired due to development. Urban uses have exacerbated ecosystem degradation through the loading of sediment and pollutants. As a result, the watershed supports some of the highest levels of contaminants in the nation, according to the Clean Water Act Section 303(d) listing. The coral reef ecosystems in the nearshore waters, including the Waikiki Marine Life Conservation District, are also threatened by these land-based pollutants.
The Ala Wai Canal Project is in the feasibility phase. The feasibility study is investigating and evaluating solutions to environmental degradation and flood damage problems throughout the entire Ala Wai watershed (Manoa, Palolo, and Makiki drainages, including Waikiki and surrounding areas). The objective is to develop a comprehensive integrated plan that recommends a coordinated approach by all Federal, State, and local agencies and the communities to improving the overall watershed health.