The U.S. Army Corps of Engineers is moving ahead with its reboot of the Ala Wai flood control project, an effort to help shield urban Honolulu from strong and fast-moving storm waters, after scrapping the previous attempt amid rising costs and controversy.

But the federal agency’s latest effort is already facing community pushback similar to the prior proposal, which abruptly ended in 2021. 

That’s largely because the corp has rejected using ecosystem restoration as part of its new plan, even though residents in Manoa, Palolo, Makiki and other parts of the vital watershed have been asking for years for the agency to seriously consider a nature-based approach to the area’s flood control.

Instead, the corps is pursuing a plan that’s centered on erecting 6-foot-high flood walls around the Ala Wai Canal and using the Ala Wai Golf Course as a flood detention basin.

“I’m just so pissed about that,” said David Kimo Frankel, an attorney who represented Protect Our Ala Wai Watershed during the group’s attempt to alter the corps’ first flood-control plan before it was halted. 

“They say they’re coming in with an open mind but then swiftly exclude nature-based (approaches) because it’s not going to be effective enough. Tell us what the criteria is – the data and the assumptions in their model,” Frankel said last week.

On Wednesday, corps project leaders said their latest analysis shows methods such as replacing the invasive albizia trees in the Ala Wai watershed’s upper reaches and restoring natural stream beds would generate hardly any flood-control benefits during a heavy storm for the 200,000 or so residents who live there, as well as Hawaii’s economically critical tourism hub of Waikiki just downstream.

Any changes to how the storm water flows down through the steep watershed thanks to those natural restoration efforts would barely be noticeable, said Eric Merriam, project manager for the corps’ Ala Wai Flood Risk Management Reevaluation Study.

“It does not mean they’re not important and don’t have benefits beyond flood risk management,” Merriam added. “Our study and our recommendation is only one piece of the puzzle for the Ala Wai watershed.”

Still, local proponents for a nature-based approach are pressing for the corps to release the methodology and data that they used to reach that conclusion. A group of state lawmakers that represent the watershed asked the corps last month to disclose the underlying data.

Sen. Carol Fukunaga, House Speaker Scott Saiki and seven other area state lawmakers sent Shawna Herleth King, an environmental resource specialist with the corps, a letter April 12 that says the corps “has repeatedly stated that management of the forest would not sufficiently reduce runoff from larger storm events.

“However, the agency has not revealed (a) how much runoff could be reduced through better management of the forest and (b) the assumptions and data that USACE has relied upon to reach its conclusion,” the letter says.

On Wednesday, Merriam said those details will be available for public review between early June and mid-July when the corps releases its draft report 

Didn’t Make The Cut

In July, the corps released nine early, possible approaches to the Ala Wai watershed’s new flood control plan, and an informal poll taken at that meeting found the nature-based approach to be the most popular among the public. 

Nonetheless, it failed to make the cut of the corps’ final five approaches, which were announced in December. The preferred, “prospective” approach relying mostly on flood walls and the golf course basin was then announced last month.

The nature-based approach was dismissed even though the agency has had more flexibility this time around to consider new ways to guard against the fast-moving storm waters flowing down the watershed’s steep, upper slopes.

Specifically, the corps is no longer required to design flood control against a so-called “100-year flood,” or a severe storm that has about a 1% chance each year of occurring. Instead, it can consider a project that would address weaker storms.

Still, ecosystem restoration failed to make the cut. It also failed to be incorporated into any of the other main approaches being considered, as a complimentary feature.

“We can’t justify a feature if it’s not meeting the goals,” Merriam said Wednesday.

“Our mission is flood risk management, and we can only add features that are effective and incrementally justified. It’s essentially saying that you can’t go out and build things because it seems like it’s a good idea.”

Reforestation’s ability to protect the communities downhill against fast-moving storm waters is “fairly minimal” because the Ala Wai watershed is so remarkably steep, he said. “Those events are extremely intense.”

Watershed restoration was actually part of the project’s original scope going back to 2001. However, that element was later scrapped in 2012 because the corps didn’t find sufficient benefits on a national level for the costs involved.  

The removal surprised Ala Wai community groups and activists, one of whom called the corps’ subsequent flood-control effort “half a project.”

Still, Fukunaga said she hopes some of the Ala Wai’s various restoration efforts, such as the ongoing “Genki Ball Project,” in which bacteria spheres are tossed into the Ala Wai Canal to help digest sludge, will find funding to thrive “even if not all of them are tied to the flood mitigation scope itself.”

“We should see where we can generate support,” she said this week.

The public can comment on the corps’ preliminary approach through Monday by visiting the city’s website on the project. The next public meeting on the project is scheduled for May 15.

Read the state lawmakers’ concerns with the corps’ new approach below.

Civil Beat’s coverage of climate change is supported by the Environmental Funders Group of the Hawaii Community Foundation, Marisla Fund of the Hawaii Community Foundation and the Frost Family Foundation.