Sea Level Rise-driven Saltwater Intrusion Could Impact Coastal Real Estate Values

As sea level rises, coastal cities and towns are growing increasingly concerned that fresh water sources used for drinking water, wastewater treatment, agricultural irrigation, and industry could be fouled by saltwater intrusion. Saltwater intrusion occurs when higher sea level forces saltwater inland at the surface or underground through porous rock and sand. When the salt water reaches fresh water intakes on rivers or underground wells, the fresh water become unfit for human consumption and most other uses.

According to a study published in the Journal Nature, millions of Americans live in coastal communities at risk of losing access to fresh water due to saltwater intrusion. KCRA in San Francisco aired a report last week that examined the threat saltwater intrusion poses to the state’s Central Delta waterways.

As sea level rises, it threatens to push salty ocean water up into delta rivers and estuaries that provide drinking water to 27 million California residents as far away as Southern California. The water is also used to irrigate the Central Valley’s farmland.

Sea level rise isn’t the only contributor to the saltwater intrusion problem. The West’s ongoing mega-drought is also drawing down river levels, which could potentially hasten the inland movement of saltwater from the sea. The only way to prevent this is by releasing more water from reservoirs or the construction of a barrier to block the saltwater, which California is trying on the West False River.

The threat to real estate owners and buyers in all of this is that any community that loses access to fresh water is a community in distress. This could cause real estate values to plummet. Clearly everyone involved in coastal real estate needs to be aware of where their fresh water comes from and how safe it is from saltwater intrusion.

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.

Buyers Need to Consider Fresh Water Sources When Purchasing Real Estate in Communities at Risk from Sea Level Rise

As sea levels rise, many coastal communities are concerned that salty ocean water will contaminate water wells that provide fresh water to millions of residents. The loss of a fresh water source would be devastating to a city or town. Trying to find new sources, if it’s even possible, could be expensive. This issue should be of concern to real estate buyers in coastal communities.

The saltwater intrusion problem isn’t theoretical. For example, in 2007 researchers at Florida State University surveyed water planners to predict what would happen if seas rose 6-to-18 inches by 2057. Half the planners were concerned that their wells would be threatened by tidal salt water traveling up coastal rivers where water intakes and wells were located.

Kenneth Miller, an earth scientist at Rutgers University, told YaleEnvironment360 this week that the combination of heavy development on barrier islands with low elevations and broad exposure to ocean water puts New Jersey and other locations around the world at risk of saltwater intrusion.

South Florida residents could get a taste of the future this summer. The densely populated region is experiencing a deepening drought that’s forcing water managers to enforce watering restrictions and move water around in canals to prevent wildfires in the Everglades. As fresh water supplies are drawn down, there’s the risk that saltwater will try to fill the void, which could put wells at risk.

Whether salt water intrusion becomes a problem remains to be seen, but the situation certainly exposes a situation that many real estate buyers in coastal areas are not aware of that’s only going to get worse in the years to come. Clearly, knowing how secure a community’s supply of fresh water, or even a private well, is from saltwater intrusion is an important point to consider when buying property in areas near the sea.

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