Rising sea levels and fluctuating lakes are threatening coastal communities

Dec 25, 2023

by Lotus Abrams

Coastal cities have long attracted homebuyers seeking waterfront properties with scenic views and beach access. Climate change, however, is causing the seas to rise and fluctuating lake levels on the Great Lakes to become more pronounced, posing a serious threat to communities by the water.

On the coast, the National Oceanic and Atmospheric Administration (NOAA) projects a rise in sea level of 1 foot in the next 30 years, and the rate is increasing, especially along the East and Gulf coasts, according to Dr. William Sweet, an oceanographer at NOAA. Sweet is the lead author for the U.S. Interagency Sea Level Rise Task Force's 2017 and 2022 reports. "Currently, we’re rising about an inch every eight years globally, and that rate is rising at an accelerating clip," Sweet says.

Sweet explains that about two-thirds of the sea-level rise is from melting ice in Antarctica, Greenland and mountain glaciers, while the other third is due to thermal expansion — the warming of the waters themselves, which causes water to occupy more space. "That accelerating piece is due to the ice melt growing," he says. "That's the wild card, and that's the concern — how much and how fast."

Coupled with the effects of storms, tides and changes in prevailing winds and currents, sea-level rise is spurring an increase in flooding events. The problem is exacerbated in some areas of the country by vertical land motion, frequently caused by human-induced groundwater removal. Norfolk, Virginia, for example, is subsiding by 2 to 3 millimeters a year, or about 1 inch every 10 years, according to Sweet.

An increase in coastal flooding is prompting several cities in the U.S. to undertake major infrastructure upgrades. "In Charleston and Miami, the stormwater systems of yesterday aren't working," Sweet says. "The increased frequency of these more disruptive types of floods are really becoming a concern in communities that now recognize they’re under threat from sea-level rise and are starting to spend money."

Communities on the shores of the Great Lakes, including the greater Chicago area, also face watery threats from climate change. Andrew Gronewold, a professor at the University of Michigan's school for environment and sustainability, explains that historically, Lake Michigan's water level has naturally oscillated between high and low extremes, but that those events were driven namely by changes in precipitation, and evaporation rates tended to remain stable. The balance is changing, however, with wetter and warmer weather, in addition to more severe storms, due to climate change.

"What we’ve seen over the past 20 years is increases in both precipitation and evaporation," Gronewold says. "In the future, we expect the swings in water levels to become even more dramatic."

For real estate professionals, it's important to understand and communicate to clients the risks associated with owning a home on the coast. Here's a closer look at how rising seas and fluctuating lake levels are affecting coastal communities in four key markets around the country, and the efforts being made to mitigate the impact.

In South Florida, where Sweet indicates sea levels are expected to rise by about a foot in the next 30 years and flooding events will increase in frequency and severity, the city of Miami drafted a comprehensive plan in 2019 to address the effects of climate change. At an estimated cost of $3.8 billion, the Stormwater Master Plan (SWMP) lays out how the city will reduce the threat of flooding, improve water quality in Biscayne Bay and protect the coastline against storm surges.

The plan's shorter-term proposals include updates to water management systems and the preservation, restoration and creation of wetland ecosystems that protect against storm surges. Long-term solutions under discussion include elevated roadways and requirements for homes to be built off the ground.

In 2021, Miami-Dade County also released the Sea Level Rise Strategy report, which recommends building on fill to raise homes, roads and sea walls to stay above sea levels; elevating homes with pilings; focusing new development on higher ground; expanding greenways; and increasing living shorelines. Some climate experts, though, say that the plan doesn't adequately warn residents and developers about the severity of the threat.

Many developers and architects already take sea-level rise into consideration when designing residential and commercial buildings near the coast. For example, architect Kobi Karp, principal-in-charge at Miami-based Kobi Karp Architecture and Interior Design, consults FEMA maps to understand wave crest heights and flood criteria when designing all high-rise residential, hospitality and retail buildings along the South Florida coast.

"We design our buildings so that the first residential floor is high enough to allow for the wave crest, and the buildings are designed to take the wind load on the building and withstand flooding," Karp says. "We also have flood panels that raise automatically on the ramps to the garages when there's a hurricane warning."

Boston is also expected to experience about a foot of sea-level rising in the next 30 years, according to Sweet, with the risk for moderate and severe flooding increasing, as well. In the past, severe flooding has typically been associated with major storms in Boston, but NOAA predicts these conditions may occur in the future simply due to tidal events.

The city of Boston is working to mitigate the impact of climate change, including sea-level rise and coastal flooding, with the Climate Ready Boston initiative. Plans include protecting shorelines with nature-based and hard-engineered flood defenses; creating new, resilient infrastructure systems; and instituting regulations for new and existing buildings that are climate resilient.

One solution proposed by the Boston Harbor Regional Storm Surge Working Group, an association of public and private sector members, is to build a sea wall and storm surge gate to protect Boston and the surrounding communities on the harbor from severe storm surges.

Storm surge gates have been proposed elsewhere, as well, like the $29 billion plan proposed to protect Galveston and the Texas Gulf Coast. The drawback to this solution, Sweet points out, on top of the steep price tag, is that storm surge gates are only designed to protect against major storm events.

"These gates aren't protecting against the sea-level rise-related flooding that's causing stormwater and wastewater systems to fail, roads to flood and property to get damaged," he says.

The situation is different in Seattle, where sea levels are predicted to rise about a half-foot in the next 30 years — half as much as in Miami and Boston, Sweet affirms. The slower rate of sea-level rise is due to the colder waters in the Northwest, as well as the region's deep, narrow continental shelf, which prevents winds from stacking up water and generating flooding. "Tides are really the dominating factor here," Sweet says.

While the region's rate of sea-level rise is slower than for the East and Gulf coasts, it is already affecting some areas, including eroding shorelines. For example, at Cape Shoalwater, located 140 miles southwest of Seattle, the beach is eroding at 100 feet per year.

According to Eric Shull, managing broker and Puget Sound Realtor at John L. Scott Real Estate, many clients in the Seattle area are aware of and concerned about the risks associated with coastal living.

"For people who are looking at waterfront property, it's definitely something that they talk about, whether it's the post and pier [foundations] or even concerns about erosion, landslides or mudslides," Shull says. "One of my brokers recently had a client who asked how climate change was going to impact their waterfront property. That's a tough thing for a broker to answer. We would definitely point them to NOAA or the University of Washington for more information."

Sea-level rise is concerning to state and local officials, as well. In 2017, Seattle released a climate preparedness report that outlined a strategic approach to tackling climate change, including rising sea levels, in the areas of transportation, land use and built environment, city buildings, parks, drainage and water supply systems, the electricity system and community preparedness.

In Chicago, the extreme fluctuation of Lake Michigan's water levels during the past couple of decades has caused lakefront erosion, beach loss, flooding and damage to homes and businesses — and the risk is increasing, according to Gronewold.

"There are enormous risks involved," Gronewold says. "We want to make sure people unequivocally have the information in front of them that says the shoreline is eroding, that water levels fluctuate and that they’re likely to become more extreme."

In 2013, water levels hit record lows due to ongoing drought and high evaporation rates, which hurts the shipping industry and jeopardizes drinking water supply. Seven years later, in 2020, lake levels rose to near-record highs. Severe rainfall that year sent waves crashing up to the third floor of some North Side residential buildings and caused the Chicago River to overflow into downtown when the city's backup system — a series of locks that reverses the river back into the lake when the river level gets too high — failed.

It's not just longer-term fluctuations in water level extremes that are cause for concern along Lake Michigan, warns Gronewold. Intense storm events can generate waves as high as 10 to 20 feet. Factor in reduced ice cover at the shoreline during warmer winters, which usually dampens waves before they make landfall, and you’ve got extremely risky conditions. "If we experience a couple of these intermittent very high water levels every two to five years along with the increasing severity of storms, it does paint a picture where there should be an assessment of risk."

While Chicago has spent and allocated millions of dollars for projects to fortify the Lake Michigan shoreline and repair eroded beaches, many environmental leaders and city officials recognize the need for a more comprehensive approach to address climate-related risks along the lakefront.

The threat has prompted some experts, including Gronewold, to advocate backing away from the coastline altogether with future development. "My colleagues and I have been thinking about this problem for a long time," he says. "I’m a big fan of retreating development from the shoreline to mitigate infrastructure damage. We’ve just seen too many homes fall into the lake."

Such sentiments may be alarming, but real estate professionals and environmental experts alike hope that, equipped with the knowledge of the risks involved with coastal living, communities will take a proactive approach to mitigating the threat of climate change. And for architects like Karp, that knowledge pushes forward the opportunity for innovation and adaptation.

"I think that technology will continue to improve," Karp says, "and give us the ability to compensate for the damage that we have done to the natural environment over the past years and decades."

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