As hurricanes ravage the southeastern United States and Congress sets money aside for disaster aid, Hawaii delegates in Washington are gearing up to make their own request for almost $200 million in federal dollars to protect Honolulu neighborhoods from potential flood damage.
The money would fund the U.S. Army Corps of Engineers plan to make the Ala Wai watershed, an area encompassing about 19 square miles in central Honolulu, more flood resistant. The city and state would be expected to chip in more than $100 million for total project costs.
Sixteen years in the making, the plan includes a 4-foot wall along the Ala Wai Canal and the construction of larger basins along streams in Palolo, Makiki and Manoa — all tributaries to the Ala Wai Canal.
“We can’t afford not having a project like this in the works and have something like a Harvey or an Iniki hit us,” said U.S. Rep. Colleen Hanabusa, who represents urban Honolulu, referring to a recent hurricane in Texas and one that hit Kauai in 1992.
Planners at the U.S. Army Corps of Engineers considered rising sea levels in creating their plan for the Ala Wai Canal, where water levels rose during April’s King Tides.
Cory Lum/Civil Beat
After a few procedural steps, the plan heads to Congress for funding. If all goes smoothly, Hanabusa expects the project to break ground at the end of 2018 or the beginning or 2019.
The proposed changes to the Ala Wai watershed are estimated to cost $306 million, $107 million of which would need to come from the city or state. It would brace the city for what’s known as a 100-year flood — a major storm that’s likely to occur once every 100 years.
State Rep. Tom Brower, who represents Waikiki, said he’s confident the state would fund its share of the project if the federal government provided its share.
Once built, the new infrastructure to the Ala Wai watershed is expected to cost almost $1 million per year in maintenance. That money would need to come from either the city or state, or another source.
The Corps had originally planned to taper off the wall along the Ala Wai Canal. After the project’s planners analyzed sea level rise, they decided the wall should remain 4 feet high along the entire canal.
“We discovered that if we extended that 4-foot wall all the way to Ala Moana Boulevard that as the sea level rose it would also provide this added benefit for protecting against sea level rise,” said Michael Wyatt, a planner at the Corps’ Honolulu office.
During the king tides in April, the water level in the Ala Wai Canal was noticeably higher.
When Hurricane Iniki passed south of Oahu in 1992, the canal overflowed, inundating the first floor of some Waikiki hotels. Storms in 1965 and 1967 also caused the canal to overflow.
This rendering shows the potential effects of a 100-year flood on Waikiki and the surrounding area without improvements to the canal.
Courtesy of U.S. Army Corps of Engineers
The blue area in the image above depicts areas where flooding would occur during a 100-year flood with the U.S. Army Corps of Engineers’ planned infrastructure in place.
Courtesy of the U.S. Army Corps of Engineers
The 2-mile-long canal was built in the 1920s, as part of an effort to convert swampland and farms into what is now the state’s tourism mecca. The canal was originally promoted by developers as helping to make Honolulu “The Venice of the Pacific.”
The tourist center’s popularity may help its chances of securing funding in Congress, Hanabusa said.
“When they think about Hawaii they think about Waikiki,” Hanabusa said of congressional members who sit on appropriations committees and hold the key to securing federal funding.
Hanabusa said Hawaii delegates must remain vigilant to see that the project makes its way into the Water Resources Development Act, which will give the Corps authorization to begin construction.
The state’s Hawaii Emergency Management Agency has identified Waikiki as a flood-prone area of heightened concern in the event of a storm, said Vern Miagi, an administrator for the agency.
If a 100-year flood hit the Ala Wai watershed area, the Corps estimates the damages would cost more than $1.14 billion. That estimate doesn’t include the economic loss the state would suffer if flooding shut down Hawaii’s tourism center.
About 200,000 people live in what the Corps calls the “inundation area” around the Ala Wai Canal. Property and infrastructure in the area is worth an estimated $9 billion, according to the Corps.
Even if the Corps oversaw the construction of added basins, some parts of the watershed would still see flooding in the event of a major storm, particularly in Makiki and Moiliili.
Hawaii’s watersheds, where water can fall from 3,000 feet at the top of a mountain to sea level in a matter of minutes, make it particularly susceptible to flash flooding, Wyatt said. In addition, global warming has many worried that large storms are increasing in frequency.
“I’ve seen two 100-year-events in the last two years, so that’s kind of a misleading term,” Wyatt said.
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