PORTLAND — Property owners, city officials, architects and researchers will gather Friday to discuss ways to save Bayside from rising sea levels, such as erecting a hurricane barrier under Tukey’s Bridge to shield Back Cove from storm surges.

But despite dire predictions of flood waters swamping Marginal Way, there won’t be discussions about what is causing the world’s oceans to rise.

“We don’t want to talk about global warming,” said Sam Merrill, an associate research professor at the Muskie School of Public Service and a speaker at Friday’s community conversation, taking place from 8 a.m. to noon and sponsored by the city of Portland and the Portland Society of Architects.

Rather then get stuck in a political debate about whether nature or man is causing climate change, he said, it’s more productive to focus on how to prepare for the future if current patterns continue.

Mirroring a worldwide trend, sea levels measured in Portland Harbor have been rising at the rate of 1.7 millimeters a year over the last 100 years – about 7.5 inches in total, he said.

However, since 1990, the rate has been 4.1 millimeters a year.

“The rate has been speeding up,” Merrill said.

Scientists have yet to determine how much seas will rise.

In the meantime, the people of Portland need to figure out how to prepare for a future in which the kind of damage that now occurs during extreme high tides and massive storms becomes more prevalent, Merrill said.

He said Portland has four choices: fortify the city’s assets, require buildings to be high enough off the ground to accommodate flood waters, relocate buildings or “remain in denial.”

He said he doesn’t want to give the city any specific advice but rather facilitate a community conversation.

Last summer, the City Council passed a resolution supporting development of a Sea-level Rise Adaptation Plan.

As part of this planning process, Peter Slovinsky, a marine geologist at the Maine Geological Survey, last week provided a City Council panel with several scenarios the city could face over the next 100 years, from a 1-foot to a 6-foot rise in sea levels.

On Friday, Slovinsky will provide an overview of his study.

Merrill will focus on the Bayside neighborhood and the Preble Street area near Back Cove Park.

Merrill has completed an analysis that illustrates the impact that different flooding and mitigation scenarios would have on property values. For example, spending $100 million to build a hurricane barrier under Tukey’s and improve drainage in Bayside would avoid the loss of $400 million in property values, according to his analysis.

Portland has targeted Bayside as an area for major development, said Paul Stevens, president of the Portland Society of Architects.

But if it looks like that area is going to be under water decades from now, people are going to pull back on investment, Stevens said.

The city’s commercial waterfront also is considered at risk. In the past, debates about the waterfront, such as whether to develop the Maine State Pier, have all ignored the issue of rising sea levels, said Constance Bloomfield, who serves on the board of directors of the society of architects.

Bloomfield said she is pleased to see city officials are now willing to discuss the issue.

“It takes a bit of courage on the part of the people within city government, both the politicians and the staff, to begin thinking about things in the future beyond the next election cycle,” she said.

The free forum will take place in Room 102 of the Wishcamper Center at the Muskie School of Public Service, 34 Bedford St., on the University of Southern Maine’s Portland campus.

Registration begins at 7:30 a.m.

Staff Writer Tom Bell can be contacted at 791-6369 or at: tbell@mainetoday.com