In the event of a catastrophic flood caused by a major hurricane, up to 7 feet of water would inundate the densely populated and economically important areas of Waikiki, McCully and Mo'ili'ili with rainwater racing down from the mountains and storm surge rushing in from the ocean.

What will prevent that from happening — options ranging from building flood walls around the Ala Wai Canal to dredging the canal — is still under study, with an environmental impact statement not expected until 2008 and construction taking about a decade longer.

And the project won't come cheap either: $60 million.

The U.S. Army Corps of Engineers and the state Department of Land and Natural Resources have been coordinating efforts on the Ala Wai Canal Project to protect homes and businesses and to save lives during floods associated with natural disasters like Hurricane Katrina.

"The Ala Wai plan is to prevent the flooding of Waikiki and the surrounding areas in the event of a 100-year flood," said Joseph Ponfiglio, chief of public affairs for the Army Corps in Honolulu. "A hurricane obviously could generate a 100-year flood, so our goal is to prevent something like that from happening. If we have learned anything from (Katrina) it's that you have to be prepared."

A 100-year flood has a 1 percent chance of happening in any given year. The Ala Wai Canal, has only a marginal ability to handle a 10-year flood but could not handle a 100-year flood, said Derek Chow, a senior project manager with the Army Corps, who is coordinating the $1.5 million flood feasibility plan.

Among the options being considered are building flood walls around the Ala Wai Canal, widening and dredging the canal to increase its carrying capacity and raising the canal bridges so debris won't block the flow of water. Diverting floodwaters to the Ala Wai Golf Course and other "storage" areas also would help keep water from overwhelming the community.

"There have been some expressions by the state, city and the public that they would rather not see any walls around the canal so we are looking at other measures such as upstream storage — recreating flood plain areas in the upstream areas of the watershed," Chow said.

Chow said major flooding in the area would cause an estimated $175 million in damage to buildings and their contents and that's not including damage to cars, the cost of emergency response or the long term economic impact to the state.

"The structural damage itself is one thing and pretty significant, but if you look at the loss to businesses and the inability for us to reopen Waikiki for a period of time, that would be an even greater loss," he said. "All the while people are out of work, we are not bringing in tourists and people aren't spending money. Basically, the area would be shut down and slowly come back to a working order. It is not like the economy is going to bounce back real quickly."

Communities across the country are taking a close look at how to protect themselves from natural disasters, Chow said.

"The October 2004 storm that caused flooding to the Manoa area is a reminder that we are not immune to such a catastrophic event," Chow said. "You've got to plan for it. We won't prevent damage, but we can try to ... reduce it to a more acceptable level."

The Manoa flood caused more than $100 million in damage to homes and the University of Hawai'i.

During storms in November 1965 and December 1967 and passage of Hurricane Iniki in September 1992, the Ala Wai Canal overflowed and caused flooding in Waikiki.

Makiki resident Frederick Gross attended public hearings on the flood control project last year and said Hawai'i is especially vulnerable to this type of disaster. Money invested in this project will be small compared with the $200 billion damage estimate from Katrina, he said.

"It's not a question of can they do it, it is a question of will they," Gross said. "Look at the money they are having to spend now in Louisiana and the money they are spending on the war in Iraq."

A final Environmental Impact Report is expected to be completed by 2008 and if the project is approved by Congress, the federal government would pick up 65 percent of the tab, Chow said.

A hurricane as destructive as Katrina also would be likely to damage Hawai'i's airports and harbors, but the state has a plan to keep emergency supplies moving and safeguard people in transit, according to Scott Ishikawa, spokesman for the state Department of Transportation.

"The main thing is to try to get the facilities up and running as soon as possible," Ishikawa said. "If something happens at Honolulu International Airport, we can always divert flights to the Neighbor Islands."

Each major airport has backup generators in place to allow air traffic controllers to communicate with planes. O'ahu, Maui and the Big Island have secondary runways for emergencies. Runway lights and terminal lighting also have backup power.

In Honolulu, passengers can be sheltered at the airport during a major storm.

The harbors also are vulnerable to hurricanes, Ishikawa said, but the harbor towers have emergency generators.

"Just like at the airports you are going to need somebody to direct traffic in and out, particularly if they are bringing in emergency supplies," he said.

In the event that the massive cranes used to unload shipping containers are knocked out, some companies have mobile cranes that can be used and many container ships now have roll-on, roll-off capability.

Disaster operation centers would be established for air and ground transportation where needed and crews coordinated with other emergency services.

"It would be a joint state-federal effort to get the harbors reopened," Ishikawa said. "The fact is we are pretty isolated from the rest of the nation, the main thing is to try to get the airports and harbors open as quickly as possible knowing we are going to be needing supplies from the Mainland."

Ishikawa said that if one island is in danger, others can help. During Hurricane Iniki, major supplies still flowed into Kaua'i from other islands.

"We can't predict how we are going to survive a Category 5 hurricane, but you just have to have a backup plan," Ishikawa said. "We are as ready as we can be."

Reach James Gonser at jgonser@honoluluadvertiser.com.