An early draft of the The Army Corps of Engineers’ “tentatively selected plan” for build-out — and build-up — of a Waikiki flood-protection plan that centers on the Ala Wai Canal will be presented at a virtual meeting today.
Here’s the bottom line: 6-foot-high flood-control walls and a flood-control basin at Ala Wai Golf Course are likely headed our way.
After approximately 25 years of study, debate, protest and reassessment, these protective measures have emerged as the cheapest, yet safest and least objectionable options — and should be advanced by the city and communities, so that now focus can be turned to making these protective projects attractive and useful.
What must not happen now is to condone building ugly, if effective structures that wall off neighborhoods and people as well as water.
The flood control plan is designed to protect Waikiki and neighboring communities — the 200,000 residents living along the Makiki, Manoa and Palolo streams, and the Ala Wai Canal, from flooding disasters caused by extreme weather that has a risk factor of 2% to 5% annually, typically described as a “20-year-storm” (5% risk) or “50-year-storm” (2% risk).
As global warming makes the likelihood of monster storms less predictable, the necessity for protective action grows with it.
The project includes floodwalls on the Ala Wai Canal and a detention basin within Ala Wai Golf Course to protect Waikiki, floodwall construction at Kaimuki High School to protect communities east and southeast of the Manoa-Palolo Canal, and floodwall construction at Woodlawn Drive and Koali Road to protect Manoa.
The walls and basins all include barriers that could reach up to 6 feet high, but the exact height of each structure will be determined at the next phase.
Proposed detention basins at Manoa District Park and Makiki District Park, along with a proposed flood wall at Kanaha, were deleted after opposition arose; the Corps determined that alternatives in the latest plan do not increase risk to lives or less-affluent communities.
Also under consideration: installation of drainage pumps. The Corps is expected to recommend other protective measures as well, such as raising at-risk residential structures on stilts.
After these locations of the flood walls and holding basins are settled, Honolulu and the Corps will address the appearance of the floodwalls, as well as the Ala Wai’s canoe launches, in an effort to avoid turning the canal into a more repulsive thing. What’s also needed is sustained effort to clean the waters of the Ala Wai, but that is a subject for another agency, and not the Corps.
The Corps has raised the possibility of a “stepped” wall on the makai side of the Ala Wai, with an elevated walkway/runners path and bike path on the Waikiki side of the floodwall at 3 feet high, and another 3-foot wall on top of that. This, or another variation, could work — and must be designed to work, to continue to allow for public use of the corridor.
Raising these walls is justified for the safety of neighboring communities, and because, in this dense sector of Oahu, the potential for catastrophic property damage, including severe harm to Waikiki, exists if action is not taken.
The end of the line for public input is quickly approaching.
Today’s virtual presentation by the Corps and the city takes place at 5:30. Link to a video presentation previewing the prospective plan, and sites for public comment at honolulu.gov/alawai, and join the meeting at usace1.webex.com/meet/AlaWai.
Next, the tentatively selected plan will be fully unveiled in a draft Ala Wai Canal Flood Risk Management “reevaluation report” scheduled for release in June, with public meetings to follow. A final Ala Wai report is expected by the end of this year or early in 2024.
