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Rising sea levels could alter life on Vashon

One morning last month, an extreme high tide collided with a blustery winter storm to create a surge of seawater the likes of which some Vashon residents said they had never seen.

Around the island, crashing waves damaged bulkheads, swept away docks and boats and came dangerously close to beachfront homes.

Experts say these types of high tide events, and even worse ones, could become frequent as sea levels rise due to profound changes in the climate that are slowing causing glaciers and icefields to melt. The issue is particularly germane on Vashon, some say, an island with 51 miles of shoreline and countless houses built close to the water’s edge.

“We’re already vulnerable to these types of situations,” said Laura Whitely Binder, a researcher with the University of Washington’s Climate Impacts Group. “You add high sea levels, and that can add to the damage potential,”

The City of Seattle, which also experienced a high-tide storm surge that day and recorded a record high tide, recently used forecasts by the Climate Impacts Group (CIG) to create a map of how rising sea levels will affect its shorelines.

The map, which was released by Seattle Public Utilities (SPU) last week along with an updated climate change action plan for the city, showed a sobering scenario: coastline areas that will be inundated daily within 40 years as well as neighborhoods that will be under water during storms and high tides.

No such sea level rise map has been made for Vashon, Binder said, but islanders can expect to see the same gradual increase in sea level as Seattle, a phenomenon scientists expect will occur as a result of rising ocean temperatures and the melting of land-based ice. The region has already seen sea levels rise about eight inches since 1870, according to King County statistics.

“There’s a robust signal,” Binder said. “The details of the individual numbers and individual projections will change over time, but the signal that sea levels will rise is a very clear signal.”

The group’s projections show that the Puget Sound will most likely see a 6-inch rise in sea level by 2050 and a 13-inch rise by 2100, an increase that could send water into low-bank waterfront homes and submerge low-lying roads during high tides.

A more recent study has confirmed the CIG’s numbers, which were released in 2008, Binder said, but a number of factors play into sea level rise, making it somewhat hard to predict. For instance, some parts of the state are projected to see either no change or a loss in sea level because shifting earth plates are causing the land to rise as well.

For Vashon, a less likely but possible scenario, according to the study, is that the Puget Sound could see as much as a 22-inch rise by 2050 and a 50-inch rise by 2100.

“It’s fairly wide, which is often frustrating,” Binder said of the projections. “People want the number, but it’s not always possible to give a definitive number.”

Binder said that while there were certainly homes on Vashon that would one day have sea water in them, islanders who live along the shoreline should be more concerned about the storm damage that will precede any dramatic sea level rise.

Climatologists predict that in the Northwest, storms will become stronger due to climate change. Combine that with increasingly high tides, Binder said, and homes on the beach will be battered by high waves more and more often. Heavy rains could also trigger landslides.

“People get very fixated on inundation maps, but it’s easy to forget about storm surges, which we’ll see more impact from,” she said.

To that end, King County recently did a study on what a sea level rise will mean for flooding on Vashon. As part of a project last year to draw more detailed flood zones on the island, the county’s River and Floodplain Management section created a map that shows which parts of the island will flood worst during a storm surge should sea levels rise.

Kyle Comanor, a county engineer who worked on the map, said that a two-foot sea level rise in Puget Sound could mean serious flooding in some parts of Vashon. Comanor explained that because of underwater topography and how waves travel, a 2-foot increase in sea level could cause a 5-foot wave during high ties storm surges. The county’s color-coded map shows that the most at-risk shorelines are on the north end of Vashon and the northern bank of Maury.

“Some parts of the island are better suited for a rise in sea level,” he said.

While the flood zone mapping was done to meet Federal Emergency Management Agency (FEMA) requirements, Comanor said, the county created the sea level rise map to give the public an idea of what the future may hold.

“FEMA does not require this work for their flood maps. … We decided to do this map to serve the citizens,” he said.

Waterfront homeowners reached by The Beachcomber said they knew climate change may one day send water into their homes, but they were trying not to worry about it yet.

“I try to not to think about things that I personally don’t have control over,” said LeeAnn Brown, who recently moved into a low-bank home on Luana Beach.

Brown said that she’s making efforts to reduce her own carbon footprint and simply hopes for the best when it comes to the future of her beach house. But beyond that, she said, she doesn’t know what to do.

“Every waterfront house here is definitely potentially at risk, I believe,” she said.

Real estate agent Emma Amiad, however, said the threat of rising sea levels is making some families rethink where they live. She said she knows of a few homeowners with low-bank waterfront properties who are considering selling their homes, especially in light of the recent extreme high tides.

“For the first time since they owned the house, the water is maybe up on their porch,” she said.

“Some figure it won’t make that much difference to them, but it might to their children or grandchildren,” she added.

But Ken Zaglin, another longtime Vashon real estate agent, said there’s as much interest in waterfront property on Vashon as there has ever been. Climate change rarely comes up when he shows clients a beach house, he said. More people, he added, ask about tsunami risks.

“I just don’t think there’s a great deal of awareness,” he said. “I haven’t seen any effect yet with buyers, but as it becomes more and more prevalent in the news and the effects of climate change begin to become more pronounced, … it will become an issue that will impact lenders and buyers very directly.”

Some who don’t live on the water have already found themselves inconvenienced by high water levels. During recent extreme high tides, or king tides, flooding has completely closed Quartermaster Drive and at times partially closed Vashon Highway along Quartermaster Harbor. On New Year’s Day, a large group of Islanders convened at Portage to clean debris that a king tide left around the road.

The county’s flood zone map shows that with a two-foot sea level rise, almost all of Portage would be overcome by waves during high tides and storms.

“We’re already very aware of the condition of those roads and how close they are to the water,” said Rick Brater, a manager in the county’s Roads Services Division.

Brater said the county pays close attention to what roads could be at risk to climate change, including low waterfront roads on Vashon. Also at risk are riverside roads in other parts of the county that are expected to see record flooding if climate change causes heavier rainfalls.

However, the roads division’s funding situation is bleak, Brater said, and it’s currently putting off some road repairs, focusing on only the most pressing needs.

For instance, in 2009 the county began design work for a project to replace the seawall along Dockton Road at Tramp Harbor, a project that Brater said likely would have taken rising sea levels into consideration. But funding got tight, he said, and the seawall replacement was postponed indefinitely.

“We know what we need to do, but we don’t have the funding to do it,” Brater said of the roads that are at risk. “The climate change issue is additive to all the other issues we’re dealing with.”

 

To see King County’s map of flood zones on Vashon in a two-foot sea level rise scenario, see http://your.kingcounty.gov/dnrp/library/natural-resources/climate/Vashon_Maury_SeaLevelRise_2011.pdf

 

 

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