The city will spend about $3.5 million to define and construct evacuation routes from coastal areas as part of an effort to ensure orderly exits from low-lying communities in the event of a tsunami or severe flooding.

Officials plan to identify and use all available roadways including private roads, state roads, old plantation tracts and military roads.

"The task is very enormous and it has to be accurate the first time," said Melvin N. Kaku, director of the city's department of Emergency Management, speaking before the City Council's committee on Public Safety and Service recently. "The entire island is, at least on the coastal side, considered low-lying areas and highly susceptible to storm surges and floods. If one is in the low-lying areas, they need to go toward the mountains."

December's heavy rains convinced North Shore residents of the need for just such a plan, as well as the need for better notification from the city in the event of heavy rains or severe flooding.

Many of those at the meeting said the rain came so fast on Dec. 11 that they didn't know what roads were open and what areas were flooded.

"We could definitely use military roads. We need to really work with the military," said Jacob Y.W. Ng, a North Shore resident.

On that day, some areas of O'ahu received as much as 14 inches of rain in 12 hours, with Hale'iwa and Waialua among the hardest-hit areas.

Michael Lyons, chairman of the North Shore Neighborhood Board, said area residents don't have a lot of time once the rain starts falling to figure out whether the deluge will threaten life and property.

"This whole flood and devastation was in a two-hour time period, and we lost millions of millions of dollars (due to damage)," Lyons said. "We have two major schools near waterways and hundreds of children involved."

In 2005, Honolulu police did a preliminary survey of roadways that would lead residents to high ground in the event of emergency, but Kaku said a more in-depth analysis is needed. If existing roads are not sufficient, new roadways will have to be built or existing roads linked together.

In the past four years, the city has experienced several emergencies that nearly prompted evacuation from coastal areas, including flooding, two tsunami watches and the Kiholo Bay earthquake.

The city must "ensure that an evacuation from coastal areas does not cause gridlock on the roadways and that any evacuation plan incorporates the most efficient movement of people away from hazard zones," according to a resolution asking the administration to study the issue.

"Being that coastal communities would be most affected (by storm surges and flooding), we need to ensure people are educated about the threat and notified quickly," said City Councilman Donovan M. Dela Cruz.

The roadway system in the city includes private and plantation roads that are not publicly accessible and could be crucial to efficiently evacuating coastal areas.

The Department of Emergency Management is requested to delineate on its emergency evacuation planning documents those roadways that are necessary for emergency evacuation from coastal areas, including the determination of which private and plantation roads are safe for such use, according to the resolution.

"I think we have to realize that it takes a long time (to map out and build evacuation routes)," said councilman Duke Bainum. "We should probably start where we think the biggest problems lie. You need to look at those evacuation routes and determine the priorities."