Throughout history cities have been built along the water, and this tendency persists in the United States today: about 33 percent of Americans live in coastal regions and 10 percent of Americans live along the Great Lakes. Yet despite the many benefits of shoreline living, which can include access to fisheries, trade, transportation, and drinking water, changing water conditions under climate change are increasingly making shoreline life difficult.

We witnessed some of these difficulties firsthand growing up. Leah was raised on a barrier island on the east coast of Florida, feeling the effects of climate change in the form of sea level rise (SLR), saltwater intrusion, and flooding during strengthened storms. Gabi grew up in New York City, largely oblivious to local impacts of climate change until Superstorm Sandy flooded her apartment building. These experiences have strongly impacted our studies.

Here we lay out some of the challenges faced by San Francisco (West Coast), Chicago (Great Lakes), New Orleans (Gulf Coast), and Miami (East Coast). By threading together struggles that stretch from west to east, north to south, across the entire United States, we wish to give a glimpse of climate resilience plans that span the nation.

West Coast: San Francisco

The traditional homelands of the Muwekma Ohlone and Ramaytush Ohlone, San Francisco was bordered by extensive salt marshes until the 18th century. These marshes acted as natural flood control, able to absorb both water and storm energy to protect the land behind them. European settlers converted many of these marshes into farmland and real estate. Shoreline ecosystems, like Ocean Beach, are already experiencing erosion as the San Francisco Bay has risen eight inches since the mid-19th century. Nevertheless, buildings have been constructed right up to the high tide line.

San Francisco Public Works is planning for six percent of the city to be flooded by SLR by 2100; stronger storms, king tides, and El Niño events will temporarily push the flooding even further. If SLR reaches four feet, nearly 28,000 San Francisco residents who are ‘socially vulnerable,’ including those who are low-income, disabled, or without access to a car, would experience daily flooding. More than 104,000 jobs would be lost, as well as shoreline infrastructure, including highways.

The City and County of San Francisco’s Sea Level Rise Vulnerability and Consequences Assessment lays out the risks to new development, shoreline open space, and local and regional transportation. A key concern is liquefaction as filled-in marshes, inundated by SLR, are at risk of liquifying during earthquakes. Despite the risks, the report does not encourage retreat from the shoreline in the popular, lucrative, and growing city.

San Francisco is already working on and planning for extensive and expensive adaptation for SLR. For example, the city is fortifying the sea wall protecting the Embarcadero, a popular tourist destination with expensive real estate. As rising sea levels inhibit the flow of stormwater out into the Bay, a large tunnel will funnel stormwater away from the Mission neighborhood to prevent flooding. San Francisco International Airport is also being fortified with a heightened sea wall. A notable exception to this proactive stance is sewage treatment; when questioned by NBC reporters, officials at a low-lying San Francisco sewage treatment plant, vulnerable to flooding in the coming decades, were unable to provide a SLR survival plan.

Efforts to restore salt marshes, a potential buffer to storm surge and sea level rise, have often been successful here: the Bay is home to one of the world’s largest inter-agency habitat restorations. The San Francisco Bay Shoreline Adaptation Atlas, created by the San Francisco Estuary Institute and its Aquatic Science Center, provides a framework for coordinated, regional adaptation planning for SLR. Despite the premium value of San Francisco land as real estate, the Atlas promotes marsh restoration as a cheaper solution than sea walls and one that can be funded by $500 million earmarked in 2016 through Measure AA.

Great Lakes: Chicago

Chicago, the traditional homelands of Tribes that include the Potawatomi and Miami, borders the vast Lake Michigan. The lakefront downtown is built on former marshland, and this clay soil absorbs waste- or stormwater poorly. The sewer and stormwater system, technically above the original ground level, drains into the Chicago River after treatment. In order to prevent sewage from then draining into Lake Michigan, Chicago’s source of drinking water, the city reversed the flow of the Chicago River away from the Lake.

The Lake is experiencing both unprecedented lows and unprecedented highs due to climate change. Warm temperatures from 1999 to 2013 prevented the Lake from forming much ice and increased evaporation, which decreased water levels. Conversely, cold winters due to the destabilization of the Arctic polar vortex led to high water levels in the summer of 2020, with low evaporation coinciding with spring snowmelt and increased rainfall. Between both extremes, Lake Michigan has oscillated in height by more than six feet over the last seven years, while its historic yearly cycle measured in inches. Stronger storms create high waves which further exacerbate the problem by digging into the Lake bottom, deepening the water and increasing wave height.

Extreme highs and/or rain have already caused flooding. This has disproportionately impacted communities of color and low income residents. Nearly 75 percent of flood damage claims from 2007 to 2016 were made by zip codes in which 93 percent of residents are people of color, and over 25 percent are below the poverty line. This may not even be the whole story; those worried about devaluing their home may not file a claim. Flooding comes with sewage overflow, coupling property damage with a public health crisis. High water levels also increase erosion of both Chicago beaches and property foundations.

On the flip side, for the Chicago River to remain flowing away from Lake Michigan, the water in the Lake must be high enough to feed the river. If the Lake drops too low, perhaps just six inches below its low in 2013, the river will revert to its former flow, bringing treated sewage water into the Lake.

Chicago is working on several projects to combat flooding, although largely without specific reference to climate change. Together with the Army Corps of Engineers, the city has been reinforcing the shoreline, mostly in the wealthy downtown and just north of it, to prevent erosion. From the stormwater side, Chicago has been building a system of sewage storage tunnels and reservoirs to avoid overwhelming treatment plants during storms. However, increasing this capacity cannot increase the speed at which water enters the tunnels, leaving room for further flooding.

Gulf Coast: New Orleans

New Orleans, the traditional homelands of the Chitimacha, is one of the world’s most vulnerable cities to climate change impacts. Combined with the impacts of increasingly intense hurricanes and tropical storms, sea level rise will likely be devastating for the City of New Orleans. SLR threatens the shipping industry since New Orleans is a major shipping center for goods coming from abroad or down the Mississippi River. The threat from climate change impacts, like increased storm intensity, is illustrated by Hurricane Katrina, which flooded around 80 percent of the city.

Underground pumps installed in the late 19th century to prevent flooding from groundwater build-up ironically caused the city to sink below sea level. On top of that, storms have intensified, overwhelming the pump systems. Levees, the current adaptation measures against flooding, are not constructed to handle more than a Category 3 hurricane’s storm surge. John Lopez, director of the coastal and community program for the Lake Pontchartrain Basin Foundation (now called the Pontchartrain Conservancy), states that these kinds of adaptation measures are not a “static monolith” as much of the public has come to believe. If the sea level continues to rise, these levees are likely to be overtaken, leading to flooding in New Orleans especially during storms of increased intensity.

One major issue with addressing the inadequate levees is the cost. The federal government, through the Army Corps of Engineers, has already invested $14.5 billion in rebuilding the levees after Hurricane Katrina. It would likely take billions of dollars more to modify or reconstruct them. Gentrification caused an additional problem: flooding has a disproportionate impact on minority groups. Previously redlined areas were marked as “undesirable” and remain primarily low income neighborhoods or communities of color. With the city’s history of systemic institutional racism and segregation, these communities remain vulnerable and are likely to be the first to flood.

With such pressing issues in New Orleans’ future, having a comprehensive climate action plan is vital. According to the city’s green infrastructure implementation program, plans include additional green spaces, trees, and water storage to help manage water levels and reduce the urban heat island effect. New Orleans faces the question of how to ride the line between climate change mitigation and innovation. The city has already included a few features that help mitigate the effects of climate change on its residents: raised buildings, wide porches, high ceilings, and transoms. With future warmer temperatures on the horizon, these features are key to keeping houses cool by allowing for air flow.

While there have been attempts to become more sustainable, there have been clashes with city design guidelines. New Orleans tends to capitalize on its culture, much of which is shown through its architecture and the layout of the city and it will be important to find a balance between sustainability and the city’s culture.

East Coast: Miami

Miami, located on the traditional homelands of the Tequesta, Seminole, and Miccosukee, faces a number of climate change-related occurrences, including king tides, tropical storms and hurricanes, and sea level rise. King tides, the highest high tide, occur between September and November in Miami Beach, with the highest water levels usually experienced during October. Some current mitigation and adaptation strategies include dune restoration and seawall improvements. The City of Miami also plans to install pump stations to drain around 7.5 inches of water in 24 hours with the capacity of draining up to 30,000 gallons per minute. While king tides occur naturally multiple times a year, the addition of climate change makes their impact more disruptive for those affected. Combined with the effect of climate change, coastal inundation events have accelerated, occurring more often than just during a powerful storm. William Sweet from NOAA stated that “as sea levels continue to rise, the flooding will become less storm surge flooding and more tidal flooding.”

Miami’s location in south Florida puts it in the paths of countless tropical storms and hurricanes. Hurricane season falls from June to November and Miami is one of the most hurricane-prone cities in Florida. It is also not uncommon for Miami residents to be forced to wade through knee-deep water or witness US Army Corps of Engineers trucks dump fresh sand onto the beaches to act as a buffer from the rising sea. This is an important adaptation strategy because if seas rise two feet, residential septic systems (owned by around 108,000 Miami properties) will become inoperable if the groundwater table increases with SLR.

Making problems worse, the Floridian peninsula primarily sits on top of limestone and its porosity allows seawater to rise from below. Miami residents say that flooded roads and parking garages are common, even on sunny days, as water seeps out from drains. While Miami residents have grown all too used to natural hazards and warnings of climate change, they say that this incident feels different and sparks a sense of panic, especially for the real estate industry and those living in older buildings.

Going Forward Across the US

The August 2021 United Nations’ Intergovernmental Panel on Climate Change report emphasized that the problems we discuss here are only going to increase as ice melt, sea-level rise, storms, and heatwaves become worse and more frequent. Yet, as a positive counterpoint, the proposed bipartisan infrastructure bill this year includes $47 billion for climate resilience. While more funds will be needed as shoreline cities adapt to climate change, it is a start.