Groundwater Pushed Up By Sea Level Rise Poses a Threat To Coastal Real Estate

When we think of sea level rise flooding, we think of salt water spilling across beaches, wetlands or sea walls and onto the land, but that’s not the whole story.

In many coastal areas, salty seawater sits in porous soil layers beneath the fresh water aquifer. As sea level rises, the salty seawater, which is denser than fresh water is forced inland where it pushes the fresh water table up toward the surface. This type of groundwater flooding is already creating a challenge for many coastal communities battling classic sea level rise flooding.

In Miami, for instance, some neighborhoods far from the coast are flooding because soils saturated from higher groundwater can no longer absorb heavy rains. The saturated soils are also rendering septic systems inoperable as wastewater that’s carried out into leaching fields cannot be absorbed by already saturated soils.

According to an article by Kendra Pierre-Louis published in MIT Technology Review (“How rising groundwater caused by climate change could devastate coastal communities”) rising groundwater presents a “potentially catastrophic” threat to homes and infrastructure. “Roadways will be eroded from below,” she writes, “septic systems won’t drain, seawalls will keep the ocean out but trap the water seeping up, leading to more flooding. Home foundations will crack; sewers will backflow and potentially leak toxic gases into people’s homes.” Pierre-Louis explores the challenges in great detail in her excellent piece.

Experts say Miami (and all of South Florida, for that matter) isn’t alone in confronting this threat. Kristina Hill, an associate professor at the University of California, Berkeley, told the Pierre-Louis that flat coastal areas with a type of geology that allows water to move easily through the ground are at risk. The list also includes Oakland, California, Brooklyn, New York, Mountain View, California and Washington, DC.

Of great concern here is that cities might spend billions of dollars on seawalls, elevating streets and properties, and other efforts to combat classic sea level rise, but if they don’t consider the threat posed by the rising water table that can defeat those measures from below the investment could be a colossal waste of time and money.

Buyers of real estate in coastal communities that are vulnerable to this type of flooding need to understand that flooding from beneath poses as great a threat to their investment as flooding on the surface. They need to make sure that properties of interest — and nearby properties and roads — have not experienced groundwater flooding and are not at risk of experiencing it during the period they intend to own a property. They also need to know if the septic system (if they’re not hooked up to municipal service) is operational, if pipes providing water and sewer service are in good shape, what government officials are doing to address the problem, and how much any efforts to mitigate the problem will contribute to their water and sewer bills and taxes.

Ultimately, with the enormity of the land area at-risk, combatting groundwater rise will likely prove as — if not more — difficult than fighting classic sea level rise. The best choice, therefore, is to prevent the sea level/groundwater rise itself by adopting renewable energy sources that slow and stop the global warming that’s driving it.

Sea Level Rise Added Billions of Dollars to Hurricane Sandy’s Storm Surge Damage

When it comes to sea level rise, buyers, sellers, owners, and real estate agents need to be aware of both the increased occurrence of nuisance flooding — tidal floodwaters that inundate neighborhoods on sunny days — and storm surges that can strike quickly and inflict billions of dollars in damages in a very short time.

A study recently released by researchers at Climate Central, an independent organization of scientists and journalists dedicated to informing the public about climate change, demonstrated the threat sea-level-rise-fueled storm surges pose to coastal communities. The researchers gathered information about Hurricane Sandy and concluded that a few additional inches of sea level rise contributed over $8 billion dollars worth of damage to the $62.7 billion the super storm inflicted on New York, New Jersey and Connecticut.

To arrive at that astonishing figure, the researchers analyzed water levels during Hurricane Sandy and compared it with an estimate of how high the water would have risen without human-caused sea level rise. Based on a conservative estimate of just over four inches of sea level rise added between 1900 and 2012, the year Hurricane Sandy struck, they estimated that sea level rise added $8.1 billion to the total tab the states had to spend repairing storm damage, including power grids and transportation networks.

The researchers noted in their analysis that economic damages may have been much higher than stated in their report. “Our estimates do not account for potential long-term economic effects, such as losses and gains in broad economic activity associated with employment and production changes across industries in the aftermath of a damaging cyclone event,” they wrote.

Climate Central’s chief scientist and CEO Benjamin Strauss, Ph.D., put the report in perspective: “Just a hands-width of sea level rise from climate change caused more than 10 percent of the damage from Sandy’s towering floodwaters. The implications are enormous. For any lesser ocean flood, the percentage must be higher.”

Clearly buyers, sellers, owners, and real estate agents can’t afford to ignore the influence ever-rising seas have on damaging storm surges when they’re evaluating coastal properties.

Sea Level Rise Reality: No Roads, No Real Estate

Communities from Hawaii to the Florida Keys are already confronting a harsh reality of sea level rise flooding. When flood waters inundate or undermine roads, they have a choice: spend millions or even billions of dollars to save the roads, or abandon them and the real estate that relies on them.

According to a recent report by Mahealani Richardson for HawaiiNewsNow, sea level rise-driven erosion recently caused 1,500 feet of highway to collapse in Haaula, a town on O’ahu. The state is spending $600,000 on emergency repairs, but a permanent solution to save the coastal highway from rising seas could cost up to $1.5 billion for a dozen miles.

Ed Sniffen, a highways administrator, told NewsNow, “It’s a huge but complex situation that we have to consider. Not only are we affecting who can drive through that area in the future, but access to that area in the future.”

Monroe County officials in the Florida Keys are facing the same challenge. According to an article by Theresa Java posted on KeysNews.com, county commissioners there are considering whether to elevate a road in Stillwright Point that flooded 91 days between September and December or abandon it altogether. The road’s fate — and the property owners who rely on it to get around — will depend on how much it will cost to save the road and, considering that seas continue to rise, how much time the repair will buy.

The county’s resiliency officer said a billion dollars probably isn’t enough to save all of the county’s 314 miles of roads. Mayor Heather Carruthers said, “This is the very beginning of very difficult decisions that governments around the world will be forced to make.”

If you search “sea level rise road” on Google, you’ll find dozens of cities and town are confronting the same sea level rise problem. Finding a solution isn’t just a cost-benefit question. Officials also have to consider the decision’s impact on local residents. In some cases, residents have threatened to sue if the government abandons their lifeline roads.

Buyers taking a look at real estate in coastal areas need to consider not only whether or not a property of interest is experiencing sea level rise flooding, they also have to consider how sea level rise flooding is impacting critical infrastructure, such as roads and water and sewer service. The floodwaters could not only prevent them from getting around and receiving critical services, they could also result in a huge tax hike if a community has to initiate projects to save the infrastructure. In a worst case scenario, flooding could force them to move.

Infrastructure issues are discussed in detail in “7 Sea Level Rise Real Estate Questions.”

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