More than 230 homes on Vashon could end up underwater if sea levels rise as much as scientists predict in the next 80 years, according to a recent report from Seattle-based Zillow.

Such a loss would equate to more than 4 percent of current island households — a combined value of nearly $175 million. The same report predicts that the Seattle metro area may lose more than 5,000 homes to the rising waters by the end of the century. In Washington state, more than 27,000 homes are predicted to be taken over by the higher seas of climate change.

The report, based on Zillow’s real estate data and information from the National Oceanic and Atmospheric Administration (NOAA), stated that across the United States, 1.9 million homes will be underwater by 2100 if the seas rise by 6 feet. Sea level change is expected to be variable across the United States — and the globe — but the authors of the report said instead of accounting for those variations, they chose to use the midpoint of scientific predictions included in a recent government report. That report, issued in June and written by scores of scientists, including lead authors at NOAA, NASA and the National Science Foundation, stated that sea level rise of more than 4 feet by the century’s end is “very likely” and that a rise of 8 feet or more “cannot be excluded.”

King County’s Jim Simmonds, a water quantity and quality supervisor with the Department of Natural Resources and Parks, said he is familiar with the Zillow report, and while he did not study its data and methodology, he said the premise is accurate.

“The concept that there are houses all over Puget Sound that are at risk of flooding in sea-level rise scenarios, we know that. We agree with that,” he said. “The conclusion stands.”

As an island in Puget Sound, Vashon will certainly be affected.

“Our understanding is that there are hundreds of homes on Vashon that are within the current 100-year flood plain or at an elevation close to it along the shoreline,” he said.

The rising tides are already apparent — and experts believe they will be more so as time passes and water continues to rise.

In the past century, Simmonds said seas have risen by 8 inches in the Seattle area. This change is visible on Vashon during King Tides. During those, water from the sound washes over a portion of the seawall at Dockton Park and floods portions of Dockton Road and Quartermaster Drive. Historically, that has not always been the case, and more change is forecasted.

“The projections are it is going to keep getting higher,” Simmonds added.

While Zillow used a 6-foot estimate, Simmonds noted there is uncertainty about how much and how quickly seas will rise, but in this area, he believes a good prediction is 1 foot by mid-century and 3 feet by 2100. Six feet, he said, is expected after the turn of the century.

“There is uncertainty there because no one knows the future,” he added.

Also, the increasing tides will vary within the Northwest because it is a geologically active area, he noted. In the central basin and south sound, water is projected to rise by 3 feet by the century’s end. But on the coast, in places such as Neah Bay, it will be less because the land is rising due to the action of the tectonic plates.

Also, Simmonds said, the effects of the same amounts of sea level rise will affect areas differently, depending on their geography. In places like Miami, flat expanses of houses and businesses stretch on for miles. There, water that is even a little higher than normal can inundate an area. On Vashon and many other places in the Puget Sound area, strings of homes or businesses line the shore and are backed by steeps hills and bluffs — and the water stops there.

In King County, Simmonds said that the current land use code dictates that newly constructed houses and homes undergoing a major remodel be located 3 feet higher than the elevation of 100-year floods. This does not mean that homes would be built on 15-foot pilings, as they are in some places along the Gulf Coast, he said, but on shorter pilings or a concrete foundation.

“The idea is to raise the house so that when the tides are coming in, if they keep getting higher, they are not flooding the house. Minimize the damage, minimize the safety risk for the residents. Flooding is dangerous, and it causes damage that costs money to fix,” he said.

On Vashon in varying degrees, real estate agents say they and their clients are paying attention.

John L. Scott owner Ken Zaglin said he discusses rising sea levels with every waterfront home buyer he works with and has presented the topic at three all-agent meetings.

“I have had clients sell their waterfront home based on concerns they had, and I expect it to impact our market more and more as the impacts become more obvious,” he said in a recent email. “For now, the bulk of the market has not felt the impact I feel we will be seeing over the next decade.”

At Windermere, owner Beth de Groen said that business has been affected slightly by rising sea-level concerns, and broker Denise Katz said that she has had clients who preferred mid-bank homes, but has not seen much concern recently.

Emma Amiad said she too has had clients discuss the issue, including a few who own low-bank waterfront and have let her know they want to move farther up and find mid- or high-bank waterfront instead.

“I am just not a fan of waterfront unless it seems really safe,” she added.

The effects of rising seas will be felt far and wide, but the Zillow report indicates that close to home Tacoma and Burien could each see more than 220 homes become submerged. In nearby Gig Harbor, some 430 houses may succumb to the rising tide. And north of Seattle in Stanwood, 500 homes may be underwater by 2100.

The climate change report that Zillow based its projections on states that the global mean sea level has risen about 7 to 8 inches since 1900, and 3 of those inches occurred since 1993. Human-caused climate change is responsible for the rate of this rise, which is greater than any during the previous 2,800 years. The report also states that while future emissions will have little effect on the sea level rise by 2050, they would affect sea level rise in the second half of the century.

That may be helpful for Miami, which Zillow projects could have more than 441,000 homes — nearly one in four houses — underwater by the turn of the century at a loss of more than $217 billion. New York City is next on the list, with more than 180,000 homes projected to be underwater by that time at a loss of $123 billion. While no Washington cities appeared on Zillow’s list of the 10 hardest hit metro areas, Florida has the unlucky distinction of having four cities, in addition to Miami, appear there: Tampa, Fort Myers, Bradenton and Naples. Boston comes in at number five, with communities in New Jersey, Maryland and Virginia rounding out the list.

In Washington, Simmonds said that the county is required to update its shoreline management plan in 2019, and climate change and rising seas will figure in.

“This is one of the topics we will be addressing as part of the update,” he said. “Is there something different we should be doing?”