It’s become fashionable in progressive coastal cities to start planning for the reality of climate change, particularly sea level rise. Locally, Sound Transit says “the Supplemental Environmental Impact Statement (SEIS) for the Long-Range Plan update will consider the potential rise in sea level and localized flooding that may occur as a result of climate change based on GIS data currently available.” Although maps of the Seattle Archipelago are an interesting thought exercise, in the foreseeable future rising seas are likely to be much less dramatic. Nevertheless, plausible sea level predictions do have implications for Sound Transit’s long range plan.
Sound Transit 1 and 2 rail lines will suffer little in the next hundred years or so, although the elevated Boeing Access Road section may become a causeway over water or frequent flooding. Although Seattle is fortunate to find most of itself at elevation, Sound Transit 3 and beyond face serious constraints. Hopefully, Seattle will allow thriving, dense neighborhoods to grow around those stations; if those station areas are under immediate threat, the value of the entire alignment is doubtful.
A wildly optimistic estimate as to when light rail might open to Ballard and/or West Seattle is 2030. A map I found that projects what the coastline might look like 50 years after that is at right.
A few immediate observations from this map:
- An approach to West Seattle on or west of 1st Ave S is a little dicey.
- Interbay is a terrible place to create a new neighborhood, suggesting an eastern approach to Ballard is more responsible.
- The idea of a “Rainier Valley Bypass” via E. Marginal Way to speed up South Link trips seems bankrupt, in particular because it would likely come after Sound Transit 3.
- South Sounder looks to be in pretty good shape; coastal North Sounder, not so much.
- The Deep Bore Tunnel is not well-positioned, but its lack of futureproofing extends well beyond the sea level.
Link to Tacoma via Fife is also problematic:
Predictions about the future are hard, and there’s no way to know if these will come to pass. The world could get serious about greenhouse gases. An earthquake or volcano could fundamentally alter our topology. More prosaically, Seattle could invest heavily in dikes, like New Orleans or the Netherlands. Regardless, the significant possibility of severe sea-level rise should be a consideration for the region’s long-term infrastructure investments.
* “Over 1 in 6 chance sea level rise + storm surge + tide will overtop” in 2080.