New data on rising sea levels helps drive zoning decisions


New research about changes in sea levels along Washington’s coastline during the coming years now has probability estimates that will prompt discussions and land-use decisions sooner rather than later.

The Washington Coastal Resilience Project’s recent report not only provides policy makers with specific data about changes in the sea level for specific areas along the state’s 3,000 miles of coastline but how the land itself will either rise or fall over time and also the probability of the ranges of sea level changes through 2150. Sea levels are going up in Tacoma for example, while much of the land itself is lowering because of geological shifts.

Until now, sea level changes were based on global data about the melting ice caps and then estimated down for local areas. The new research estimates rising water levels but also changes of the land elevation for points only five to seven miles apart along the coastline.

“We basically zoomed in a lot more than previous studies were able to do,” said University of Washington Climate Impacts Group researcher Harriet Morgan. “This is the best available science for Washington State.”

The report provides ranges of sea level changes for 171 different sites along Washington’s coastlines. Several of those overlapping examination points provide information about Tacoma, specifically the Tideflats, which includes one of the region’s largest industrial centers. Based on results from the study, it is likely that Tacoma could see between seven and 14 inches of higher sea level by 2050 and 18 to 39 inches by the end of the century. The study then used the data to determine the statistical likelihood of each level of variations in those predictions.

“While there is an abundance of scientific evidence demonstrating the role that climate change has on (Sea Level Rise), localized data and projections are rare, according to the report. “This new, risk-based information will allow planners and developers to better assess the impacts of SLR on their projects along Tacoma’s waterfront.”

The three-year study was conducted by the Washington Department of Ecology and Washington Sea Grant through a grant from the National Oceanic and Atmospheric Administration.

Tacoma was one of two pilot communities that worked with researchers to examine potential impacts of both urban and rural communities. Tacoma, for example, has detailed data and risk probability that will allow for more advanced planning and maintenance of infrastructure like roads and bridge as well as the future siting of key community assets.

That is where the study’s probability research comes into the discussion, since things like hospitals and fire stations must remain open and operational during floods or disasters. Parks, on the other hand, can simply close for a few days or weeks if they are flooded without much impact to the surrounding community. Areas with a high likelihood of flooding caused by rising sea levels would need sea walls or other flood-control designs if a developer eyed them for medical centers that wouldn’t be required for recreational areas.

“The study gives them more information to develop those risk-benefit decisions,” Morgan said.

The City of Tacoma is now looking for ways to best share the information to the community, developers and decision makers.

“That will take us on that next step,” said the city’s Chief Sustainability Officer James Parvey.

The new research comes as the city is embarking on a subarea plan of the Tideflats, which will review all of the land-use, zoning and environmental issues of the working waterfront. That means the research will certainly come up in those discussions, most likely along with ways to mitigate the rising waters with regional developments rather than just flood control features specific only to any new development.

“These are some of the conversations we have to start having around the city,” Parvey said.

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