Dorchester County, Maryland, sits on the eastern edge of the Chesapeake Bay. It’s the fourth-largest of the 23 counties in the state. By century’s end, it could drop down to the 14th-largest, thanks to some of the fastest sea-level rise in the world.
High Tide in Dorchester is a lovely and frightening documentary on the impacts, current and potential, of sea-level rise in this salty, marshy, and deeply historic part of my state. Except where otherwise noted, the information in this post comes from that documentary, which I heartily recommend.
The What and the How of Local Sea-Level Rise
Most of us know the sea is rising, and we know the basics of why, but of course there is more to the story than the basics. I’ve discussed some of this in other posts (for example, here and here and here), but Dorchester is a good place to see all of it come together in a worst-case scenario already well underway.
Besides glacial melting and thermal expansion, which are more or less global in their impact, there are several other, more local or regional causes of sea-level change, and by a weird coincidence they all come together in Maryland. These are:
A redistribution of water formerly held near the poles by gravitational attraction to the masses of ice on Antarctica and Greenland. As the glaciers lighten, this water sloshes back away from the poles, raising sea levels in other places. Maryland is one of those places.
The Gulf Stream runs along the surface of the ocean, like a river in the sea, until it gets near northern Europe. By then it has gotten a lot salter through evaporation, and so it sinks and continues on as a deep-water current, part of a global cycle of moving water. But the fresh water melting off of Greenland’s glaciers is diluting that salty water, making it slower to sink, causing the entire Gulf Stream to back up a bit—and that backed-up water also raises the sea-level in Maryland and parts nearby.
At the same time that the water rises, the land in the Mid-Atlantic region is sinking. This one, for once, isn’t caused by humans. Instead, it’s North America slowly readjusting itself to the melting of our glaciers some 12,000 years ago. The weight of the glaciers pushed the northern part of the continent down, creating a bulge just to the south. So with that weight off, northern areas are gradually rebounding (partially offsetting sea-level rise) while we just as gradually subside (adding to sea-level rise).
Erosion isn’t sea-level rise, but the faster the sea rises, the more quickly the lands erode.
It all adds up. Near the beginning of the documentary, the host—a white-haired, though still spry, gentleman—stands on what was the baseball diamond where he played as a boy. He’s standing in three feet of water.
Three feet of water on what was dry land within living memory—and the average rise globally is only about eight or nine inches so far.
The speed of sea-level rise is increasing. Global average rise is likely to hit two feet within the next 30 years. Depending on how much greenhouse gas ends up being pumped into the sky, it could top five feet by century’s end. What is that going to mean for Dorchester?
And Dorchester County is so flat that every one foot of vertical rise translates into five horizontal miles of land lost to the sea.
The Human Side of Things
Holland Island was once a well-to-do community, but is now just marsh with scattered dead trees. Its last house washed away in 2010. On Hooper’s Island, graves are falling into the water—the eroding shoreline is scattered with pieces of coffins and human bone. Farm Creek Marsh, as the name implies, was once farmland and still has the visible remnants of a settlement. The families of people who owned businesses there still live nearby. These are radical changes happening quickly enough that worlds change noticeably in a generation—or less.
Islands that once supported thriving communities have been reduced to marsh dotted with ruins and old graves. Towns shrink. Farmland reverts to swamp. Schools open late or close early as high tides creep across roads, obstructing buses. Snowplows are called into service any month of the year to sweep flood debris off low-lying roads.
If you live in Dorchester County, especially if your family if from the area, you already know all of this. You cope with the tidal flooding, the salt-water intrusion, the public events rescheduled in deference to the tide. You, or someone you know, has lost land, lost familiar landmarks, lost property value, lost a community, to the incoming salt water.
You may or may not attribute all of the above to climate change.
Many people living in the area attribute the losses to erosion, which is indeed part of the problem. And it’s true that there would be erosion in at least in parts of Chesapeake Bay even if sea level were stable (I have just confirmed this with my mother, a retired geologist). And while sea-level rise unquestionably makes erosion worse, it’s difficult to say which erosion is climate-related and which is not.
But as the documentary points out, the flooding and the salt-water intrusion (which is basically flooding that comes up inside the soil, rather than flowing along on top of it) are distinct from erosion and are wholly climate-related.
In some contexts, such as the conversion of marsh to open water, it can indeed be difficult to disambiguate erosion from rising seas. Did the water come up, or did the land go away? But where the land has not gone away, where it has just become wetter or saltier or both, that is not erosion.
“Nuisance flooding,” or “sunny day flooding” refers to saltwater flooding not associated with storms—no rain, no storm surge, just water coming up where it shouldn’t. Tides naturally vary, both over the month and over the course of a year. Winds can push water towards or away from shore even in good weather, too, adding a few inches to tidal extremes on occasion. Even were sea level not changing, we might expect to see an abnormally high tide wet a waterfront property now and then.
But, ask yourself, is such flooding getting more common?
When the abnormal high tide that once happened every year or so becomes a monthly or a twice-monthly occurrence, that’s not erosion. Something is changing.
Dorchester County is not the only sea-level rise hot-spot in the region. To a lesser extent, it’s happening all through the Mid-Atlantic. I’ve seen water creeping up into the streets in St. Michaels. I’ve seen fishing piers entirely underwater near Berlin. Nobody builds roads or fishing piers where they’re likely to flood semi-regularly—these structures are older than the current sea level is. Sunny-day flooding is becoming common in parts of Virginia, due to rapid land subsidence caused by unsustainable groundwater removal, plus the regionally-intensified effects of climate change.
There are other regions with their own hot spots. For example, though much of coastal Florida, sea-level rise is complicated by the porous limestone bedrock; build a sea wall to keep the rising tide out, and the water just flows through the bedrock and rises up on the other side to the exact same level as that of the sea. Lots of places have their own issues. Lots of people are facing much faster sea-level rise than the global average.
The future is not going to look like the past.
Sea-level rise, and the other symptoms of climate change, are not politics. Politicians may argue and disagree about how to respond to climate change, but the water itself doesn’t care whom you vote for, it just flows across your lawn.
The question is, what to do about it?
The people in Dorchester, and in Delmarva more generally, have a long tradition of connection to place, of attachment to the waters, marshes and forests that make up their home, and to the people, the human communities rooted in these places. These are inter-generational connections, and they don’t just wash away. Nor do they need to.
If emissions can be lowered, sea-level rise can be slowed, perhaps enough to allow the communities of low-lying areas to adapt. Buildings can be raised. Shorelines can be stabilized against erosion. Infrastructure can be moved back away from the water so that marshland can expand inland even as its outer edges are drowned by rising water. We need marshes to protect us from hurricanes and nor’easters and to provide breeding grounds for marine life, including the animals that go into the region’s famous seafood. We have a lot of options.
But to save communities in sea-level rise hot-spots will require partnerships between these communities and the wider world. Climate change is a problem no one can solve alone.
But we can solve it together.