Column: Rethink Ala Wai flood mitigation plan

We are currently bombarded by the media with stories about climate change and the threat of imminent massive flooding of the economic engine of Waikiki. While flood mitigation needs to be addressed, the current U.S. Army Corps of Engineers’ plan is not the answer.

The Army Corps plans to construct dams in the natural streams flowing within Palolo, Manoa and Makiki. Putting a 33-foot tall, 75-foot wide, 110-feet thick, 400-foot long earthen and concrete structure in a naturally flowing stream destroys what makes our streams and islands special. The Army Corps project would require the removal of the trees and native plants that grow on our stream banks.

The Army Corps’ plans require that its new detention basins be kept free of debris. This will be tasked to the city, as the Army Corps does not maintain what it builds, although they will repair it if it breaks. We all know the city is overwhelmed and has a poor track record of keeping detention basins free of debris. What will happen to neighbors who live downstream from these dams if they break? Ka Loko Dam on Kauai springs to mind.

The Army Corps also proposes four-foot-high walls along the Ala Wai Canal to protect Waikiki. However, the plan neglects to point out that the areas mauka of the wall — Makiki, McCully, Moiliili and Kapahulu — would still flood the same as if the wall had not been built. Only Waikiki would be dry. Is this equitable flood mitigation?

Waikiki is already gravely threatened by sea-level rise, much more so than by the 1% chance of a 100-year flood. Spending hundreds of millions of dollars to protect Waikiki from potential flooding from the mauka side does nothing to prevent the current situation of storm drain covers lifting during king tides, or walkways in front of hotels being covered by water during high tides.

There are better ways to protect our communities from flooding.

First, in June, the City Council limited the amount of impermeable surface that can cover lots for new houses. We need to take the next step to reduce the amount of hardcover in, and runoff from, our communities.

Second, make better use the Ala Wai Golf Course to retain floodwater. Reduce the elevation of the golf course and surround it with berms to increase its retention capacity. Unfortunately, the city is poised to enter into a long-term lease with the $50 million Topgolf project that will increase the amount of impervious surface and eliminate some of the potential of the area’s ability to retain flood waters.

Third, better manage the forests on our hills so that the watershed can effectively retain flood waters.

Fourth, people living along the streams need to learn to avoid polluting or blocking the streams so that water going into the Ala Wai and out to sea is clean.

Finally, we need to consider both technological and green options that the Army Corps has refused to fully consider based on antiquated engineering constraints.

There is doubt about this project among our legislators. Only $220 million in federal funds would go toward this project. The matching $125 million would come from Hawaii taxpayers’ pockets, as well as any construction cost overruns and ongoing maintenance and operations costs. On July 3, the City Council unanimously passed Resolution 19-145, requesting that Mayor Kirk Caldwell not sign the agreement with the Army Corps until the project has been re-evaluated. In April and May, seven of the eight affected neighborhood boards passed resolutions asking Gov. David Ige to re-evaluate the project.

With our beautiful environment, Hawaii should be a model for ecologically friendly flood mitigation, not something rushed through because the money is dangling.