Thursday, September 29, 2022

High ground and the lack thereof

Another thread we've been hammering for a awhile. 

A common, perhaps even the standard framing of rising sea levels is that it's a existential threat for all coastal cities, and while I understand the desire not to downplay the crisis, this isn't true. For cities with relatively high elevations like Los Angeles (a few low-lying neighborhoods, but most of it hundreds and some of it thousands of feet above sea-level) or cities with at least moderate elevations and little danger from tropical cyclones (like almost all major cites on the West Coast), we are talking about a problem but not a catastrophe (The remnants of hurricanes we do see in California are generally more good news than bad. Kay broke our recent heat wave and gave some relief to firefighters). Some beaches will be lost and a few people will have to relocate, but compared to drought and triple-digit temperatures, that's a fairly manageable situation. 

 Of course, the real tragedy of this framing is not that it overstates the threat to the West Coast, but that it dangerously understates the immediate and genuinely existential threat to many cities on the East and Gulf Coasts. 

 From CNN:

• Storm surge: Some 12 to 18 feet of seawater pushed onto land is forecast Wednesday for the coastal Fort Myers area, from Englewood to Bonita Beach, forecasters said. Only slightly less is forecast for a stretch from Bonita Beach down to near the Everglades (8 to 12 feet), and from near Bradenton to Englewood (6 to 10 feet), forecasters said.

Lower – but still life-threatening – surge is possible elsewhere, including north of Tampa and along Florida’s northeast coast near Jacksonville.

 What's happening in in Fort Meyers is horrifying...

But imagine what an eighteen foot storm surge would do to the slightly higher but far more populous Jacksonville.

From Wikipedia:

Fort Meyers
    10 ft (3 m)
Population (2020)
 • Total    86,395

    16 ft (5 m)
Population (2020)
 • Total    949,611

And while we're at it...


    6 ft (1.8 m)
Population (2020)
 • Total    442,241 

These storms are going to get stronger and the seas will continue to rise for the foreseeable future. Look up the elevation for cities that are likely to be hit by hurricanes. Anything less than twenty-five or thirty feet is basically playing Russian Roulette.


  1. West Coast (selected major cities)
    Seattle 53 meters
    Tacoma 74 meters
    Portland 15 meters
    San Francisco 15 meters
    Los Angeles 93 meters
    San Diego 19 meters
    Vancouver 0 Meters (seriously:

    East Coast (selected major cities)
    New York City 10 meters
    Baltimore 10 meters
    Norfolk, VA 2 meters
    Charleston, SC 6 meters
    Boston 43 meters
    Miami 2 meters

    With the surprising exception of Boston, everything on the East Coast seems to be far more vulnerable to storm surge than the West Coast. But the West Coast has Vancouver (population 662K), so it is hard to be definitive On the East Coast is Halifax (440 K) is about 23 meters so it follows Boston, meaning Canada's risk profile is the exact reverse of the United States.

    As Mark notes, these elevations are not uniform, but they are also very, very different in terms of risk profile.

  2. As an improper Bostonian, allow me to point out that quite a bit of Boston and Cambridge are quite low: Much of MIT and the Back Bay (despite currently being adjacent to a large body of fresh water) are in the 10 to 15 meters above sea level range.

    The obvious point is that "average height" and "how much of that area is well below average" are different things. Here in Tokyo, there's a lot of filled/reclaimed land (in what had previously been Tokyo Bay) that will all be under water should the Greenland ice cap melt, which it's doing faster and faster every time someone takes new measurements, and even faster when new types of measurements are invented and it's actual behavior becomes more clear.