How rising groundwater due to climate change could devastate coastal communities (2023)

Fae Saulenas doesn't want your sympathy.

Saulenas spent last winter, her desirous winter, with her 46-year-old daughter Lauren in Saugus, Massachusetts, in a house without a working stove. Saulenas is 70 years old. Lauren is paraplegic from brain injuries sustained in utero, blind, and suffers from a seizure disorder among other disabilities. In winter it is not uncommon for nighttime temperatures in Saugus to fall into the late teens. The two could not survive long without heat, so they relied on space heating without a stove. But the electricity bill to run it was $750 in February alone, and only one room was heated.

Saulenas does not tell this story to generate sympathy, but as a wake-up call. Water tables, he says, are rising, seeping into gas lines and eating out furnaces from the inside out. This happened to her. And he wants you to know that if you live near the shore, even a mile, two, or three miles away, the water could reach you too.

Chances are you've never heard that rising groundwater poses a real and potentially catastrophic threat to our infrastructure. The roads will erode from below; septic tanks do not drain; The walls keep the sea out, but catch water that seeps in, causing further flooding. The foundations of the house will break; Sewers will back up, potentially allowing toxic gases to leak into people's homes.

Saugus is a small town about 10 miles northeast of Boston. On the maps, water is one of the defining features, as the River Saugus and its tributaries meander through the city and through the swamp to the Atlantic. Saulenas bought his house in 1975 in the middle of these salt pans, cut off from the Atlantic by the Revere Beach peninsula.

Given the proximity to the ocean, the source of recent problems seems obvious: rising sea levels. Sea levels in the region have risen 20 centimeters since 1950, and this change has not been linear. Sea level is rising faster today than it was a generation ago: about one centimeter every eight years. But the water that kept Saulenas cold didn't come from the sea, at least not directly.

Its problems began in 2018 when it lost gas, and therefore heat, due to water seeping into an underground pipe. It was a problem that would last for several years. The water would enter the gas grid and your utility, National Grid, would be forced to shut off the gas. Then National Grid tried to figure out where the water was coming from, repaired the leak, and pumped out the water.

Officially, National Grid has not identified the cause of the problem. But Saulenas thinks the groundwater is to blame.

Even under normal circumstances, the cast iron pipes that make up about a third of Massachusetts' National Grid infrastructure are susceptible to rust and corrosion. She believes these pipes, which once sat comfortably above the water table, are now subject to intermittent flooding during seasonal floods that push up the water table. And it's this rising groundwater that she believes got into the gas line, flooded her gas meter, and eventually corroded her furnace.

How rising groundwater due to climate change could devastate coastal communities (1)

“The problem is huge. We underestimated the flood problem.”

Kristina Hill, an associate professor at the University of California, Berkeley, to whom Saulenas reached out for answers, agrees. "She wondered, is this something that's coming from sea level rise? And obviously the answer is yes,” says Hill.

Hill is one of several researchers trying to get the public and lawmakers to take the risks of rising groundwater seriously. Unlike sea-level rise, where the dangers are obvious, groundwater rise has largely gone unnoticed. Hydrologists are aware of the problem and it's academic research, but it hasn't materialized in any significant way outside of these bubbles. Groundwater rise is only briefly mentioned in the latest edition of the National Climate Balance Sheet, published in 2018; it is absent from many state and regional climate adaptation plans and even flood maps.

A 2021 study in the journal Cities found that coastal cities rarely consider groundwater rise when conducting a climate vulnerability assessment. "They're mostly talking about sea level rise and storm surges," says Daniel Rozell, an engineer and scientist at Stony Brook University who wrote the 2021 paper. "But there weren't many questions about what will happen to groundwater."

The effects on existing infrastructure and planned climate adaptations can be catastrophic. Unplanned remedial measures with rising groundwater are in vain. Billions of dollars in infrastructure need to be upgraded. And it will likely affect a much larger area than most flood maps show. A 2012 study by researchers at the University of Hawaii that found groundwater at risk from flooding found that the area at risk nationwide was more than twice the area at risk from rising water levels alone.

Any coastal area where "the land is really flat and the geology is [the kind of] loose material that water moves through very easily," says Hill, "where this is really going to be a problem." This includes places like Miami, but also Oakland, California, and Brooklyn, New York. Silicon Valley communities like Mountain View are vulnerable to rising groundwater, as is Washington, DC. Globally, the endangered area includes parts of north-west Europe and coastal areas in the UK, Africa, South America and south-east Asia.

"The problem is huge," says Hill. "We underestimated the flood problem."

And because of the way groundwater moves, vulnerable people may not know until it's too late. "One of the most important things about groundwater is that the rise in groundwater levels precedes any surface flooding," says Rozell. In other words, we will experience groundwater flooding long before the ocean knocks on our door.

The water under our feet

It may seem intriguing that rising sea levels could lead to a rise in groundwater. At first glance, the two don't seem related, but the connection is really simple. The fact that it has been ignored for so long reflects our tendency to dwell on problems that we can easily spot.

To understand the connection, it is good to first understand something about groundwater. The water embedded in the subterranean sediments started out as surface water, like rain or snow, and eventually seeped out. A layer of saturated earth lies beneath a layer of unsaturated earth; The boundary between the two is the so-called groundwater table. And in many coastal areas, this meter-thick layer of saturated soil rests on salty seawater. When sea level rises, groundwater rises because salt water is denser than fresh water.

And that's not the only connection between the ocean and groundwater.

"Groundwater normally flows into the sea," says Rozell. “Along the coast there is what they call a submarine outflow of groundwater. You might even notice it when you go to the beach at low tide. When you stand in the water, you can feel the cold water right at the edge, on the sand. And that's groundwater that's constantly flowing into the ocean."

Therefore, any protection designed to prevent sea level rise from encroaching on land must also consider how groundwater can be drained.

How rising groundwater due to climate change could devastate coastal communities (2)

"It has the ability to affect millions and nobody pays attention to it."

What is arguably the first major study in a leading scientific journal examining what sea-level rise might mean for water tables was published in the journal Nature in 2012 by University of Hawaii researchers Kolja Rotzoll and Chip Fletcher. The study follows a report by researchers from the US Geological Survey and Yale University who were studying what would happen to groundwater off the coast of New Haven, Connecticut, if sea levels rise. In both cases, the researchers found that the two would ascend together.

"We looked at well logs and found that the water table in the coastal zone rises and falls with the tide," says Fletcher. “And then we realized that there is a direct connection between the ocean and the water table. And when the ocean rises due to climate change, the water table will rise, eventually flooding the land. So we're going to have all these swamps in built-up areas and around roads where we really don't want them. And it turns out that's a form of sea level rise that's more damaging in many areas than people classically think, as the ocean overflows the coast and becomes inundated.

And we're already seeing the effects.

danger to human health

When you talk to experts about groundwater rise, it often turns out that it is more complicated and difficult to adapt to than sea-level rise. Any solution to one aspect of the problem can create a cascade of others. Take something as simple as hygiene, for example. Typically in most United States, when you flush, one of three things happens, depending on where you live: The toilet flushes into a sump, septic tank, or sewer. But rising groundwater poses increasing challenges for all three.

The pits are essentially concrete cylinders with an open bottom and perforated sides. Especially in coastal areas, cesspools that should be dry are constantly being flooded, says Josh Stanbro, senior director of policy for the Honolulu City Council, who was primarily responsible for the city's resilience until last January. "Now they're always wet," he says. Microbes stay alive because they're wet, and with so much more water around, they can escape.

And Honolulu isn't the only city with this problem. Miami-Dade County has similar problems with septic tanks, which theoretically provide a filter layer that septic tanks do not. But for this filtering, the systems need a layer of soil half a meter deep, and this layer shrinks as the water table rises. Already, 56% of the county's systems are regularly affected by storms. By 2040, that number is estimated to rise to 64%. Faulty sewage systems can contaminate local aquifers that a community depends on for drinking water.

An alternative solution is to move houses and businesses that are currently in septic tanks or wells to sewer lines. In Miami-Dade County, the estimated cost of this change is $2.3 billion.

Sewage systems aren't a panacea either, warns Berkeley's Kristina Hill. “Most American sewer pipes, both plumbing and plumbing, usually break because we poorly maintain them. We're like an international joke," he says. "People start civil engineering conferences in Europe with slides about how bad American systems are to relax the audience." These cracked sewage pipes allow groundwater to seep in. And in places like New York and Boston that have so-called combined sewer systems, rainwater and raw sewage mix, leaving less space in the pipes. As a result, as the water table rises, places like the community of Jamaica Bay, New York, tend to see liquid spurting out of gullies at high tide.

Newer cities tend to have systems where rainwater flows through one pipe and sewage flows through another. But when the pipes fill up with groundwater when it rains, the rainwater still has nowhere to go. In both cases, according to Hill, there will be further flooding.

There's also another way that rising groundwater could turn our sanitation systems into killers.

"The Bay Area has so much underground pollution from military use and from the tech boom in Silicon Valley that it left a lot of nasty stuff in its wake," says Kris May, a coastal engineer and climate scientist who founded the Pathways Climate Institute. . "And what often happens is that we put low-income houses in those areas after they've been rehabilitated. But they still leave a certain amount of contamination in the soil, and these regulations were based on not raising the water table."

Now the water table is rising. In doing so, it saturates the soil and releases pollutants such as benzene. These chemicals are very volatile and, like gases, can easily find their way down drains and into homes.

This is the impact of rising groundwater on a single system: wastewater. But it can involve much more. Buried power lines that are not properly sealed will short out; the foundations will begin to rise under the pressure. Some fear earthquake faults could even come under pressure.

How the water finds its way

To protect themselves from sea level rise, cities are resorting to the same means they have used for centuries: dams and dikes. Boston has proposed a 175-mile seawall called the Sea Gates Project. Miami has a $6 billion proposal for a 20-foot boardwalk. New York has proposed its own $119 billion, 10-kilometer project called the New York Harbor Storm-Surge Barrier. Homeowners from Florida to California are putting up barriers to keep the ocean out. But the basic problem of all these interventions is the same: A wooden walkway holds back the sea, not the groundwater.

In some areas, where the ground is relatively impermeable, it is possible to build a breakwater or dike to slow the rise in groundwater levels. But then you have other problems. Remember that water flows into the ocean. A barrier that prevents groundwater from rising with sea level also prevents rainwater, e.g. B. recent rains, flows into the sea.

"If you don't let the water run into the sea, you kind of have to pump it over the wall. And that's basically what the Netherlands has been doing for several centuries,” says Rozell of Stony Brook. But that can also cause problems because many of the places these levees are working so hard to save, much of Lower Manhattan, much of San Francisco and Boston, were built on swamps or landfills or both. "When they pump, the floor sinks," says Hill.

And even if cities were willing to go that route, not all places can. "There are many conditions where you can pump all day without lowering the water table," says Fletcher of the University of Hawaii.

Remember that groundwater is water that seeps into the interstices, or pores, of sediments. In some places, like Miami, "the pores are so big you just pull water out of the ocean estuary," says Fletcher. “You can pump as much as you want, and it keeps coming out of an endless body of water”: the sea.

Planners are often unaware of the problem. In 2009, the Maldives, a low-lying island nation, held the world's first underwater cabinet meeting to draw attention to the damage done by inaction on climate change by big polluters like the United States. The message was clear: they are drowning us. Currently, the country is already dealing with the consequences of rising sea levels and is consolidating its outer island communities on a new island called Hulhumalé. It was designed to withstand rising sea levels. However, the project did not take into account the rising water table.

"They didn't understand that groundwater levels will rise as sea levels rise," says Fletcher. When the sea rises just two feet, which is estimated to be the case by 2040, most of this new island will be an uninhabitable swamp.

When she explained this to the project's lead designer, "he just looked at me, he was speechless. It's like he couldn't understand what he was saying," says Fletcher. "All the billions of dollars they spent on this thing and they didn't build it high enough.

eroding history

There's at least one place where you can see people measuring groundwater rise in near real time. The Strawbery Banke Museum is located in Portsmouth, New Hampshire near the banks of the Piscataqua River, just a few miles from the Atlantic Ocean. The buildings have been preserved to provide a glimpse of three centuries into the past, but also to provide a glimpse into the future. Some of the structures, including the city's second oldest house, are flooded from below.

“We receive these super tides, royal tides, which raise the water by more than half a meter above normal. And so we're starting to see water seeping into our basements," said Rodney D. Rowland, director of facilities and environmental sustainability at Strawbery Banke, during a visit to the museum in late September. Crouching in basements whose ceilings are too low for most adults to stand on, it's easy to see the watermarks of past forays into the water table.

The museum took a two-pronged approach. The first element is public education. "One of the cool things we're going to add is a kiosk that connects to sensors that have been placed in the ground around the museum," Rowland said. “And they will track the movement of the groundwater, [plus] the salinity, the temperature, the height of the water. And so visitors will see that there is water under their feet.

But the museum must also preserve the buildings. And that goal must now be weighed against fighting the rising waters. In one of the houses, "we made the decision to do away with the so-called summer kitchen," Rowland said. “There was a fireplace downstairs where they cooked in the summer. We removed and placed a block of granite.” They had to do this because the old chimney acted like a candle wick, drawing water from the basement into the rest of the building.

"So now the remaining chimneys are preserved," he added. "No water can get through here. But we missed that piece of history. And that's going to be a constant struggle with how much we're losing to salvage what we can."

In a way, Rowland is lucky. His state of New Hampshire is at least aware of the danger of rising groundwater and includes it in its plans. But New Hampshire is an exception. Many other countries with longer coastlines will have to deal with the problem in the next few years, since not only buildings but also human lives are threatened by this invisible risk.

Less than 50 miles offshore in Saugus, Fae Saulenas plans to move to higher ground, but not without making a fuss. She has written to lawmakers, the National Grid and the press to try to draw attention to the issue. “Ground water is very important to me. And it's important to me not just because it's profoundly impacted my life, but because I believe it has the ability to impact millions of people," he says. "And no one is prepared and no one is paying attention."

Kendra Pierre-Louis ist Senior Climate Reporter im Gimlet/Spotify-Podcast „How to Save a Planet“.

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