Tragedies that ring the continents

kw: book reviews, nonfiction, climate change, sea level, flooding

I approached Rising: Dispatches from the New American Shore, by Elizabeth Rush, with a skeptical attitude. The book, though filled with stories of people facing tragedy, was actually a pleasant surprise. Ms Rush is a thoughtful, energetic, and compassionate writer. She is definitely not pushing the über-leftist anti-everybody-who-doesn't-agree-with-hyped-climate-propaganda agenda. She visited a lot of people who live along the coasts of the Unites States, particularly those who had recurring flooding problems before "climate change" was "a thing"; she did her best to winkle out the factors that are increasing their suffering; and she tells their stories.

She introduces her subject by describing her first visit to Jacob's Point, Rhode Island, soon after she moved nearby a few years ago. She spoke to long-term residents and others who had know the area and described for her the impact of rising sea level on the marshes. A marsh by the seaside has a way to grow vertically as sediment is brought in by natural processes. Many marsh plants send roots uphill and upwards also, moving away from encroaching salt water. Building a road alongside a marsh blocks this inflow, and gives the migrating root structure nowhere to go. Even without filling a marsh, we can kill it this way.

I knew already, though, that the biggest factor causing "rising sea level" along much of the American coastline, particularly the East Coast, is that the land is sinking. The dissected appearance of the coastline, particularly in New England, is diagnostic of sinking land. Why is it sinking? The technical term is isostasy, or recovery from a past distortion. In this case, the cause is glacial rebound of the northern North American continent because a few miles of ice that were there during the most recent ice age are no longer there. In mid-continent, centered roughly on western Ontario and northern Minnesota, land is rising. How fast? Something less than a centimeter per year, or about 3/4 meter (2.5 ft) per century. Then, why is the land sinking along the East Coast? The ice was a lot thinner there. The ice pushing down the center of the continent caused the edges to rise. Now, as the center rises, the edges are going down.

This doesn't mean that rising global temperatures caused by the the greenhouse effect aren't making the ocean get a little deeper. It just means that this is a minor effect, but it is troublesome because it adds to an existing problem. So let's look at the subject of the first chapter, Isle de Jean Charles, Louisiana. First, images of the area southeast of Houma, including this island community:

These were taken from Google Earth. The panel on the left is from 1990; on the right, from 2015. One must look closely to see that many of the scattered bits of land in the various lagoons that line the southern coast, seen in the 1990 panel, are missing in the 2015 panel. A more prominent feature of both panels is a dark green area...except it has moved over the 25 year span. In 1990, the area north of Isle de Jean Charles was a salt marsh, and looks very dark green. Further to the northwest, west of Chauvin, is what looks like an ordinary piece of coastal land. It was marshy, but upland and more of a fresh water marsh. By 2015, the salt marsh north of Jean Charles is all under water, and the land west of Chauvin is now salt marsh. The difference in water level from one picture to the next is just a couple of feet. That is all it takes.

This picture shows Jean Charles and some surrounding territory, in the same time periods:

In this case, the 1990 imagery at this resolution is grayscale only. But it shows what we need to see: the longish island was significantly larger, and there were more bits of land scattered throughout the bays 25+ years ago. Take note of the small roadway that crossed from left to right in 1990, that had mostly vanished by 2015, and the larger one to its north, that appears impassible now. Prior to 1970 or so, the island had 4-5 times the land area compared to today. I wish I could have located a satellite image from late 2018, after the exceptional hurricane season. In Rising I read that Isle de Jean Charles now hardly exists outside the narrow strip bounded by the levee system. Most of the residents have already moved inland. The residents are native Americans, and have been enabled, financially, to move due to persistent activism by tribal leaders to obtain Federal aid. Prior to the early 2000's, they were ignored by both state and Federal aid agencies.

This is not all passive changes in water level. Higher water means that hurricanes and other storms can wash away more soil, and the channelization of the Mississippi River over the past century has resulted in very little replenishment. This area is part of the river's delta system. It is worth noting just a few things. The major problem in the area, climate or not, is the channelization of the Mississippi River, that cut off sediment replenishment; secondarily, there is subsidence that every delta system experiences as soil slowly compacts due to gravity pressing out water that it contained when it was first deposited.

All around the US, the author tells of her visits to places in Maine, Staten Island, both northern and southern Florida, and the San Francisco Bay. In some places, the land is subsiding due to compaction, as in Louisiana and S.F. Bay; in others such as Maine, glacial rebound is dragging the land underwater, a few inches per decade. In all these areas, however, governmental inaction coupled with over-development has been the greatest and most tragic force behind the destruction of coastal wetlands and the coastal landscape in general. Two stories of human blindness and greed known to me come to mind:

1) The Rapid City Flood of 1972.

When South Dakota was first settled, by people came in wagon trains up the flood plain in the valley of Rapid Creek. They took note of debris in the trees partway up the valley walls. When they were ready to stop for the night, they would carry everything of value, particularly food, and drive the animals, up to terraces and ledges above this flood line. When they settled Rapid City, they settled on those terraces, which are geomorphological remnants of earlier levels of the flood plain in the distant past. I lived in a house on such a terrace from 1982-86. It is 50 feet above the flood plain.

Later residents with less wisdom built homes and businesses further down, some even right on the flood plain. They installed a "flood control basin", Canyon Lake, upstream. It was designed inadequately, and a big rainstorm that dropped 11 inches of rain in 12 hours caused the flood control dam to burst. Water coursed through the town, destroying hundreds of homes and businesses, killing more than 270 people, and stacking up automobiles from a few car lots like clams on a shelly beach, downstream of town.

When we moved to Rapid City in 1978, areas on the flood plain outside town (now the town had laws against building on the flood plain within city limits) had already been rebuilt with mobile home developments. They are sitting in the crosshairs of the next flood.

2) Newport Beach "view homes", throughout the Twentieth Century.

I was taking an Engineering Geology course in 1971, and we learned about landslides and other earth-engineering matters. The professor, Dr. Martin Stout, is a person I greatly admire. He showed us the sand hills of Newport Beach, and described this scenario:

• An early developer noticed that these hillsides had a great view of the ocean.
• The development company persuaded the city or county government to issue permits to build ocean view homes.
• To get the best view, on each rather steep lot, a cut was made to flatten the land, and the sandy dirt so removed was dumped and leveled so as to extend the flat area beach-ward.
• Each home was built mostly out on this fill dirt, sometimes with pillars installed into the soil to "stabilize" it.
• On such a hillside (there were several), a few dozen such houses were built, sold, and occupied by people who love an ocean view and will pay for the privilege.
• Things rock along fine for a few years.
• An extra-rainy season occurs. The sandy soil gets soft and the houses start falling down, each into the back yard of the one below.
• The homeowners below sue the owners of the homes now in their back yard, for trespass or whatever their lawyer suggests.
• The city or county steps in, condemns all the dwellings involved, and has the homes bulldozed. 
• The land is graded back to an even hillside. Ground cover plants are planted.
• Five to ten years pass. Everyone on the city council or county council that currently has jurisdiction has been replaced with "new faces."
• A development company persuades them to issue permits to build ocean view homes.

On some of these hills, this had happened three times by 1971. When people are this shortsighted, how much hand-holding can we do? And there weren't even any hurricanes!

Genuine sea level change is real, but it is not happening nearly as rapidly as the natural cycles I've mentioned, such as glacial rebound and subsoil compaction. Governmental regulations of the past actually made things worse for people who received aid to deal with a flooded house: They were required to use the money to rebuild the house exactly where it stood before. Only recently have rules in some places been changed to allow people to take their payout and move further uphill or inland to rebuild there.

Here is the actual magnitude of climatic sea level change: 

• Sea water has a moderate coefficient of volumetric thermal expansion, approximately 0.00025 for temperatures between 0°C and 5°C, the temperature of the oceans deeper than a few tens of meters.
• Unlike fresh water, sea water does not get less dense in the lower degree or two before it freezes. It keeps getting more dense.
• The average depth of the oceans is about 3,700 m.
• Multiply this by 0.00025, to get 0.925. That means, if the entire ocean becomes one degree warmer (Celsius), it will get nearly one meter deeper.
• The best figure I can find is that the average ocean temperature has risen 0.2°C in the past century. That means the oceans are 0.185 m (about 7 inches) deeper due to thermal expansion.

The wild card is melting of ice caps. Contrary to what many vocal critics worry about, melting of the the Arctic ice cap cannot contribute to sea level rise because that ice is floating already. The major ice cap that can cause trouble is Antarctica. If it all melts, the seas will get roughly 60m deeper, or 200 feet. That would be catastrophic. The secondary ice cap is Greenland. It has about a tenth as much ice, so melting it entirely would mean a 6m, or 20 ft, rise in the oceans. Less catastrophic, but still catastrophic. I cannot find a good estimate of how many people would be displaced by a 6m rise; the reports are all over the place. It is somewhere between 1/20 and 1/5 of the human race, between 400 million and 1.5 billion.

I have no way to know how likely this is. There was a report just this week that the deep ocean is actually cooling, due to delayed effects of the "Little Ice Age" of the 1700's and early 1800's. Some portions of the Antarctic ice cap are also being strengthened rather than weakened, as this cold pulse works its way down through the miles of ice. But other portions of both Antarctica and Greenland are softening.

What is Ms Rush's conclusion? Humans are to blame for the human tragedies, it is true. But local matters are bigger and more damaging than global effects. It is hard for people to think in terms of centuries, or to plan for the ages. She writes of a "five generation window": most of us knew our grandparents and we may know their stories, and we expect to know our grandchildren and tell them our stories, and maybe some of our own grandparents' stories also. For most of us, that is about a one-century window. But we see evidence everywhere that most decision makers do not plan beyond their next promotion, or the next election, or sometimes the next paycheck. At least 1/3 of Americans have less than $5,000 in any kind of retirement savings account, and 1/5 of them have nothing...zero. zip, nada. I can understand for the 12% that live below the "poverty line", saving isn't feasible. But for the rest, who could save but don't, their "golden years"...not so golden.

We need a national consciousness like the wisdom of the people in those wagon trains, looking for signs of old floods to inform them of safe places to spend the night or locate their new homes.