Hundreds of property owners on Oahu have been told their land has been reclassified and is now in a "high-risk" flood zone as the result of remapping by the Federal Emergency Management Agency.

Owners with mortgages will be required by lenders to buy flood insurance if they find themselves in the zone. Others with mortgages on homes already in a flood zone may have to pay more for coverage if new maps now have them in an area of higher risk.

The change, effective Nov. 5, could reduce the value of certain properties by imposing stricter development requirements for new structures — such as increasing how high off the ground a building must be.

Officials roughly estimated that 1,000 properties were affected by the remapping on Oahu but were unable to provide the total number that were moved into the high-risk flood zone for the first time.

The largest area affected includes residences and businesses on the west side of Waimalu Stream below Moanalua Road. The area — including more than 160 parcels, the Waimalu Shopping Center, the Harbor Center, Goodwill and Best Buy — was previously classified as "undetermined risk" and did not require federal flood insurance.

"I’m kind of in shock," said Troy Sumic, a Waimalu resident for more than 30 years. "I’m kind of wondering how they came up with their assessment. We’ve never had a flood where I live."

Sumic said the area has storm drains, whereas some people outside the "high-risk" flood plain don’t. "Where’s the logic in that?"

Two other areas significantly affected by flood map revisions are along Halawa Stream, and Kawainui Marsh near Coconut Grove in Kailua.

"All of a sudden, we’re in a high-risk area," said Calvin Nishio, who has lived in Coconut Grove for 35 years.

FEMA has designated flood zones as low risk, moderate risk or high risk.

Coconut Grove was flooded to a depth of several feet when the marsh overflowed during heavy rains on New Year’s Eve 1987. But residents say there hasn’t been a problem with flooding since the levee makai of Kawainui Marsh was improved in 1997.

"They did so much to improve the flood control," George Takamori said. "I just don’t get it."

Takamori, who lives on Kihapai Street, said that during a recent meeting with FEMA he asked state and federal officials to point out the source of potential flooding.

"I couldn’t get … the answers," said Takamori, a retired commercial photographer.

Halawa resident Joanna Barroga, who lives on Ohekani Loop, said the risk of flooding might be reduced if the city would clear and dredge Halawa Stream.

She said the stream is full of debris and that the last time the waterway was dredged was 25 years ago.

"Why didn’t they do their job to avoid flooding?" said Barroga, who has lived in Halawa for more than 35 years.

Barroga said a lot of residents are retirees living on fixed incomes, and that she feels they will have difficulty paying the new flood insurance premiums.

In 2012, the average flood insurance premium nationally was $650, according to Floodsmart.gov.

Ross Sasamura, director and chief engineer of the city’s Department of Facility Maintenance, confirmed that the portion of Halawa Stream between Salt Lake Boulevard and Kamehameha Highway was last dredged in the 1990s.

Sasamura said the city has a project in process to dredge Halawa Stream near Ohekani Loop. However, he said, structural improvements to the stream are needed to contain extreme flows during a major flood.

"There may be a need for the construction of flood walls or other containment features in order to remove properties from the identified FEMA floodway," Sasamura said.

Homeowners with mortgages are required by lending institutions to have flood insurance if their properties are located in a risk zone.

FEMA offers insurance for owners that covers $250,000 to the property and $100,000 to its contents for an annual premium of around $500 a year, officials have told residents.

Takamori said the high-risk classification of his property means he’ll have to obtain flood insurance, but his mortgage exceeds the $250,000 coverage and he doesn’t know what kind of insurance his lending institution will require.

"The lender is the one who’ll say, ‘You have to cover this,’" he said.

Barroga said that while her mortgage is paid and flood insurance is optional, her family was considering doing renovations to the property and taking out a loan for the work.

"I think it’s going to be more difficult," she said.

She said the high-risk classification also means a change in the value of her property. "I’m sure it’s going down," she said.

Federal officials said they base their risk guidelines on a 100-year flood or a major flood that has a 1-in-100 chance of occurring in any given year.

Major breaks in levees have occurred in the past 10 years, including the 2005 failure in New Orleans during Hurricane Katrina.

FEMA spokesman Eric Simmons said his agency and the city decided to do a detailed study of streams and levees on Oahu.

Simmons said the remapping of flood zones in Coconut Grove was based on detailed topographic information reflecting residual flooding in an area protected by the Kawainui Marsh levee.

"Levees reduce but do not eliminate flood risk," he said.

Simmons said a detailed study of flood hazards along Halawa Stream also reflects areas of flood risks.

Carol Tyau-Beam, the state National Flood Insurance Program coordinator, said property owners who think they have been inadvertently placed in the high-risk flood zone, they can apply to FEMA for a "Letter of Map Amendment."

Residents said filing an amendment is probably their last option, because it would require hiring a surveyor.

The last change in flood insurance maps on Oahu became effective in 2011.

FEMA officials said the process involving the latest revision began in 2010. There have been two public meetings about the changes on Oahu — one on Aug. 29, 2013, and another on Aug. 12.

The sessions were held in conjunction with the state Department of Land and Natural Resources and the City and County of Honolulu Department of Planning and Permitting.

FLOOD ZONES RECLASSIFIED
A large area in Waimalu is among the Oahu neighborhoods that have been reclassified as “high-risk” flood zones, meaning homeowners and businesses will have to buy flood insurance.