When it comes to flooding in the U.S. mid-Atlantic region, hurricanes barely rate

When I was a kid, the most exciting weather event I encountered was Hurricane Bob. If memory serves, we went inland when it came, and I think we were staying with a family friend. I remember seeing the dramatic footage of floating cars along the Massachusetts coast. I remember intense winds, and the surreal calm of the eye passing overhead. It cemented hurricanes in my mind as Serious Business, and nothing I’ve seen since then has dissuaded me of that view.

I also remember Nor’easters, with their cutting cold and violent winds, but we never left town to avoid one of those. To me, they were exciting events, that often knocked out the power for a while, which meant we got to light everything with candles. It turns out that for all the attention paid to hurricanes, in the mid-Atlantic region of the United States, almost all coastal flooding events come from non-tropical storms.

The most recent paper was published in the Journal of Applied Meteorology and Climatology and compared extreme coastal flooding events from tropical cyclones and mid-latitude weather systems in the Delaware and Chesapeake Bays from 1980-2019.

Callahan looked at the past 40 years of measurements from several National Oceanic and Atmospheric Administration (NOAA) tide gauges in the Delaware and Chesapeake Bays. This helped him to quantify the storm surge — the rising sea as the result of atmospheric pressure and winds associated with a storm — from these large weather events.

While coastal flooding from tropical weather events tend to get a lot of media attention — and actually have a higher average surge level — Callahan said that midlatitude weather events can produce flood levels just as severe and occur much more frequently in the Mid-Atlantic.

“About 85 to 90% of our coastal flooding events here in the Mid-Atlantic come from the midlatitude events; they don’t come from the tropical cyclones and the hurricanes,” said Callahan. “You can get strong nor’easters that have just as high coastal inundation levels and cause just as much — if not more — damage than tropical cyclones.”

One of the reasons that the midlatitude events can cause so much damage is that, unlike the tropical systems that commonly impact coastal areas in the southeastern United States before hitting the Mid-Atlantic, the intensity and size of midlatitude events are most difficult to forecast and can strengthen quickly without much warning. Also, while tropical systems usually peak and are well-formed storms before reaching the Mid-Atlantic, a nor’easter can strengthen quickly right on or just off-shore of the region. Additionally, mid-latitude systems are often bigger in size, move slower, and remain over our region for longer periods of time.

That makes a lot of sense to me. Hurricanes are huge, easily visible, move over the planet almost like some kind of entity. They make for great television, in part because you can spend weeks tracking them from formation – usually off the coast of western Africa – until they dissipate. The disparity in coverage and perception seems to be from a combination of the incentives of our news entities, and the nature of the storms.

Because they happen frequently in the cold season — from November to March — not much attention is paid to how nor’easters cause coastal flooding. Instead, more attention is paid to the amount of ice and snow and wind that the nor’easters bring and not as much focus is on the coast.

“Our attention is diverted between these other impacts or factors of these storms in the winter and spring, but this is where most of our coastal flooding comes into play,” said Callahan.

I also have to imagine that flooding is more dangerous. It’s possible that the colder water means fewer chemical reactions, so less of that danger, but the risk of hypothermia is astronomical in those conditions, and all that ice in the floodwater can also do direct kinetic damage to things. I’d be inclined to think the increased frequency is responsible for the higher numbers from mid-latitude storms, but the authors also point out that even if we’re just looking at the biggest disasters, hurricanes don’t even make the halfway mark.

Of the top 10 largest coastal flooding events in the Mid-Atlantic, tropical weather systems account for only 30-45% in the Delaware and upper Chesapeake Bays and 40-45% in the lower Chesapeake Bay. If you expand out further, tropical systems make up approximately 10-15% of all coastal flooding events.

The authors go on to make the shocking prediction that as sea levels rise, coastal flooding will get worse.

I think this is a valuable lesson in how to think about climate change. We’re still living in the society that created this problem, and that is trying to avoid solving it. The things we’re shown aren’t always the things at which we need to be looking. That’s true in all areas of life, of course, but I think it’s particularly true with climate change. A lot of what’s happening is invisible to us until it’s too late to do anything but fight for survival. Science lets us see that stuff, but we’re actively discouraged from looking closely. There’s a miasma of propaganda that makes it hard to tell what’s going on, and I’m worried that that’s going to lead us to overlook some pretty important things

It’s good to have this information, and I hope more people become aware of it. In terms of overlooking things, all we can really do is pay attention and, as always, organize.

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  1. Katydid says

    A thought: for the most part, coastal land on the East Coast is either highly commercial so it will be rebuilt, heavily-polluted and a place where poor people live (so nobody in charge cares), or belongs to rich people, who will be paid to build and rebuild and re-rebuild, etc.

  2. says

    Last I heard they were in the process of elevating the town of Norfolk, VA, as well as the naval base there.

    At some point, I feel like people are going to realize that it’s not worth the expense of rebuilding.

    But yeah – we’re stuck with a system designed perpetuate all of our most destructive behaviors. It worries me.

  3. Katydid says

    Oh, right, I remember reading about Norfolk, that’s reliably underwater a distressing amount of time. Charleston, SC, too. And the Outer Banks of NC, which are regularly destroyed by hurricane and/or flooded. And of course Miami…

    Yeah. 🙁

    Related topic: I seem to be the only only in the world who remembers this, but around 2008-ish, there was an animated program on (I believe?) The Science or the Nat Geo channel–whichever one it was that showed the series A World Without People. It was a mock documentary that told the life of a woman born in California in the year 2000, whose family fled the droughts and dust storms. She moves to New York as an adult (so…2025?) and meets a man who becomes her husband, who is on the engineering team that’s building a flood wall around NYC, and she builds rooftop gardens. They have a daughter who moves to Canada as an adult because south is unlivable, and the original woman dies in 2100, age 100, on a planet no longer inhabitable by humans.

    Do you know what I’m talking about?

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