If you’re listening to updates on Hurricane Lane, you’ve likely heard public officials talking about the risk of overflowing of the Ala Wai Canal, a historic waterway that borders the northern side of Waikiki.

For more than a decade, federal officials have been working on how to mitigate a 100-year flood that could inundate the state’s tourism center.

Federal officials are expecting the canal to overflow this weekend but they’re not sure to what extent.

Ray Alexander, the chief of Interagency and International Services for the Army Corps of Engineers, said Friday that “the canal has flooded in the past. I believe it’s safe to say that with the rain forecast it will flood again, the impacts of which we’re not prepared to say at this time.”

The question is when Hawaii will see a 100-year flood that could cause $1.14 billion worth of destruction in Waikiki.

This rendering by the U.S. Army Corps of Engineers shows what could happen to the Ala Wai Canal and surrounding neighborhoods during a 100-year flood.

U.S. Army Corps of Engineers

As reporter Sophie Cocke wrote in this 2013 Civil Beat project, developers destroyed wetlands, productive farmland and fish ponds to build the canal in the 1920s. The primary motive was to create more developable land reminiscent of Southern California.

But the developers made a serious mistake. They realized in the midst of building the canal that if it flowed into the ocean at Kaimana Beach as planned, the currents would carry any pollution right in front of Waikiki Beach. That, plus the fact that money was running out, led the engineers to abandon the original plan to create a second outlet.

The result is today’s canal, a contaminated waterway that has frequently violated federal and state water safety standards. In 2006, a 34-year-old man died a gruesome death after he fell into the water by the Ala Wai Boat Harbor and got infected by flesh-eating bacteria. 

The U.S. Army Corps of Engineers has been preparing for the possibility of a 100-year flood for more than a decade. The plan involves creating detention centers along the Makiki, Palolo and Manoa valleys to catch water. The project also requires building a wall along the canal to block water from flowing into Waikiki.

Just a month ago, the Army Corps announced $345 million in federal funding to make the project a reality. The funding was granted faster than local Army Corps officials were anticipating, which could jumpstart design and construction.  

Person peers over the bank of the Ala Wai Canal during a high tide at 3pm at the same time that Hurricane Hector was skirting south of the Hawaiian Islands. If Hurricane Hector hit Oahu, this compounded w/ the King TIde could have devastated and flooded Waikiki. 9 aug 2018

A man peers over the bank of the Ala Wai Canal during a high tide earlier this month at the same time that Hurricane Hector was skirting south of the Hawaiian Islands.

Cory Lum/Civil Beat

But actually finishing the flood control mitigation is still a long way off. Honolulu Mayor Kirk Caldwell backed federal funding but said earlier this week that he doesn’t support building eight-foot-high walls along the canal. And the city and state may have to come up with money for annual maintenance.

The latest version of the project calls for walls that are an average of four feet high, with some as high as six feet in some sections depending on the elevation.

The City and County of Honolulu is in charge of notifying residents if they need to evacuate to higher ground. Caldwell said Friday if the canal overflows this weekend, Waikiki residents and tourists should seek shelter on the second floors of buildings.

Nick Grube and Marcel Honoré contributed reporting to this story.

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