PORTLAND – The owners of more than 1,800 properties in Portland will face building restrictions or be required to buy flood insurance if flood maps published this month by the Federal Emergency Management Agency take effect.

The vast majority of those properties are on the city’s inhabited islands: Peaks, Cushing, Cliff, Great Diamond and Little Diamond.

City officials are reviewing the federal data because they have developed models that more accurately measure the potential risks posed by big storms, said Director of Planning and Urban Development Penny St. Louis Littell.

“We are expending a great deal of time and effort to make sure the map is accurate for the entire city, as we did on the waterfront,” she said.

FEMA published the maps on Sept. 2, beginning a 90-day appeal period that ends on Dec. 2.

Residents affected by the FEMA maps need to review the data and file an appeal through the city. The application for appeal is available online.

FEMA officials have said they will seriously consider new data submitted by property owners or municipalities, and will revise the maps to correct any mistakes.

The maps are scheduled to take effect in June. They are the basis for federal flood insurance, which is required on mortgages for property in flood zones. Development is restricted on properties in high-hazard flood zones, so the owners cannot replace buildings that are more than half damaged by storms.

The federal government began a program to map floodplains in 1969. In 2003, Congress authorized updating the maps and putting them into digital format, using aircraft with laser technology. FEMA is now creating new floodplain maps for most coastal communities in York and Cumberland counties.

The agency is using topography, water depths and historical data for winds speeds and waves to calculate how high waves could get at the peak of a storm that, statistically, happens only once in a century.

In Portland Harbor, the initial calculations led FEMA last year to put much of the waterfront in a high-hazard zone. That would have stopped construction on Portland’s piers.

To challenge the designation, Portland hired Robert Gerber, an engineer for Sebago Technics in Westbrook who specializes in computer modeling of environmental systems.

Gerber used sophisticated modeling, and data from the Portland International Jetport and a weather buoy, to recalculate the effect of waves and wind on Portland Harbor. He determined that the peak, sustained wind speed in a 100-year storm would be 52 mph, not 71 mph, as FEMA had assumed.

The effort proved successful. The agency’s new maps removed much of Portland Harbor from the high-hazard zone. FEMA also removed the area around Mill Cove in South Portland.

Portland officials have now hired Gerber to apply the same analysis to the city’s islands.

Gerber said his analysis shows that the federal maps are accurate for areas that are exposed to the open ocean, such as the back shore of Peaks Island. However, they overstate the risks to areas that are sheltered or face the mainland, he said.

The pattern holds for all coastal areas he has studied, from Harpswell to Kennebunkport, he said.

Geber is working for individual property owners and for Kennebunk, Kennebunkport, Biddeford, Cape Elizabeth, South Portland and Harpswell. The Old Orchard Beach Town Council next will consider hiring him.

The new maps would not add any restrictions in Falmouth. FEMA did not update its maps for Brunswick, Freeport, Cumberland or Yarmouth.

Other than Old Orchard Beach, Gerber is not accepting any more clients because he’s so busy preparing appeals for the clients he has.

“I have never had to tell people, ‘I can’t do anything for you,”‘ he said. “But this 90-day deadline is kind of absolute here.”

Staff Writer Tom Bell can be contacted at 791-6369 or at:

[email protected]