Honolulu Flooding Control Plan Updated

August 28, 2020

The Army Corps of Engineers released a revised flood protection plan for Honolulu neighborhoods that includes fewer impacts on natural streams and residential properties within the watershed.

The updated Ala Wai Flood Control Pro¡ject remains contentious because of a canal wall and large pump that are still included in the proposal, The Honolulu Star-Advertiser reported Wednesday.

The project was undertaken to reduce major flooding in a 100-year storm event, loss of life and long-term economic damage within the 19 square miles (49 square kilometers) of the Ala Wai Watershed, which encompasses Waikiki, Manoa, Palolo, Makiki, McCully, Moiliili and the University of Hawaii.

The new plan detailed in an engineering report completed Aug. 6 recommends focusing on evacuating water without holding it in upper sections of the watershed valleys, the Corps said in a statement.

The plan will still require a large pumping station on the Ala Wai and concrete flood walls along the canal plus catchment basins to detain floodwater and debris at the Ala Wai Golf Course, Kanewai Field and Hausten Ditch.

Among the plan’s new features is a Woodlawn Bypass at the Manoa Marketplace to divert water from impacting the University of Hawaii at Manoa.

Other revisions include eliminating six catch basins in the upper portions of Manoa, Palolo and Makiki valleys meant to detain floodwater and debris and one in-stream debris catchment structure in Manoa.

Congress passed a $345 million emergency appropriation in 2018 for investment in projects in flood-prone areas.

The project’s cost is now estimated at $417 million. Additional funds must come from the state and Honolulu, while the Corps and the city must reach an agreement to enact the plan.

The Honolulu City Council has contracted with engineering consulting firm Oceanit to conduct community outreach and solicit alternatives to the Corps’ plan, which met resistance including protests and a lawsuit filed by the group Protect Our Ala Wai Watersheds.

Opposition to the previous Corps plan largely stemmed from residents opposed to condemning private property.

The new proposal “requires no homes to be purchased or condemned for the pro┬íject,” Ala Wai project manager Jeff Herzog said.

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