What are the Impacts of Sea Level Rise?
Flooding during high tides and storms will worsen in many locations in the U.S. due to sea level rise.
Key takeaways
- Impacts from sea level rise will differ across the U.S.’s diverse coastlines.
- Many places in the U.S., particularly along the East and Gulf coasts, will experience more frequent and widespread flooding from high tides and storms as sea levels rise over the next 30 years and beyond.
- High tide flooding is already happening at twice the rate it was 20 years ago along U.S. coastlines.
- Additional impacts, including erosion, property damage, and habitat loss will reshape coastal landscapes creating structural, environmental, and economic challenges for many communities.
Sea Level Rise is Making Flooding Worse
Sea level rise varies from place to place and so does its impact on the diverse coastlines of the United States. As sea levels rise, many coastal places will experience more frequent and widespread flooding during high tides and storms over the next 30 years and beyond. This is because sea level rise adds height on top of already existing sea levels. For example, given 4 inches of sea level rise, a water level that used to reach 12 inches high during high tide or a storm would now reach 16 inches or more during the same event. Moreso, that extra height can push a flooding event further inland, causing greater damage.
This will only get worse as sea levels rise further in the coming decades and longer. For example, moderate high tide flooding which causes damage to buildings and infrastructure currently happens less than once per year on average in East and Gulf coasts communities. However, by 2050 these same flooding events are projected to occur 3-10 times per year.
What does it mean when the 2022 Interagency Technical Report says there will be a “flood regime shift” by 2050?
The 2022 technical report provides information on extreme water levels, ranging from rare to common flooding events, to assess current and future flood exposure considering sea level rise. By 2050, there is expected to be a "flood regime shift," where the frequency of moderate high tide flooding will exceed today's frequency of minor flooding due to rising sea levels. This means that tides and storm surges currently causing minor floods will lead to more severe flooding events, impacting infrastructure and requiring emergency responses more frequently.
The impact of sea level rise has already been felt by many coastal communities in the U.S. Due to sea level rise, in 2024 the U.S. now experiences five more days where flooding occurs compared to 2000. These impacts are being experienced most prominently along the low-lying East and Gulf coasts of the U.S. where sea levels are rising the fastest.
To find out more about changes in flooding related to sea level rise in your area, go to the Coastal Sea Level Explorer.
Sea Level Rise Also Impacts Coastal Communities’ Land, Infrastructure, Economies, and People
In addition to flooding, there are a variety of other impacts from sea level rise that coastal communities are already experiencing. Many of these impacts are happening at the same time, leading to extra stress on communities. Communities that lack resources to protect themselves or to adapt are at even higher risk of harm.
At the shoreline, the added height from sea level rise can speed up erosion. Erosion can impact natural habitats and lead to the loss of land and property. When combined with flooding, erosion can damage roads, bridges, sewage systems, power plants, and other key infrastructure for the community. This can lead to health risks through the spread of waterborne diseases.
Below ground, sea level rise can cause saltwater to seep into freshwater aquifers, known as saltwater intrusion. When saltwater mixes with the fresh groundwater, the water becomes unusable for drinking and agriculture. Furthermore, coastal and marine ecosystems that support industries and provide natural storm protection, resources and ways of life are all at risk of changing or degrading due to sea level rise.
Sea level rise impacts can lead to economic hardships for a community. In particular, communities that rely on coastal tourism, fisheries, and shipping may feel the impacts most deeply. Plus, many coastal communities also have a rich history that ties their culture to the water. These changes could lead to a loss of heritage sites or cultural practices.
However, actions are being taken in many coastal communities to help plan for and address these impacts.
Broad Impacts of Sea Level Rise
There are many factors that influence the impacts of sea level rise on coastal communities. Diversity in coastal landscapes and environments, social and economic factors, and coastal development all play a role. Together, these factors shape how sea level rise impacts are felt in different locations and by different communities.
Direct impacts from sea level rise include increases in flooding, coastal erosion, saltwater intrusion, elevated groundwater, and landscape changes. Building on these are what’s known as cascading impacts. These happen because of the direct impacts and include infrastructure and property damage, health risks, economic challenges, social and cultural changes, and habitat loss.
An introduction to each impact is provided below, but more information can be found in the Coasts, Energy, Transportation, Economics, Health, and Regional chapters of the Fifth National Climate Assessment report.
Flooding: Flooding, especially during high tides and storms, is one of the most immediate impacts of sea level rise for many communities. Flooding can damage homes, businesses, and infrastructure, and potentially displace people or result in health risks.
Erosion: A naturally occurring process, erosion results in the breaking down of the land over time. Rising sea levels can exacerbate coastal erosion as the water reaches higher or further inland. This can impact natural habitats and lead to the loss of land and undermine property and infrastructure.
Saltwater Intrusion: Below ground, saltwater can seep into freshwater aquifers as sea levels rise, a process known as saltwater intrusion. If the saltwater mixes with the fresh groundwater, it makes it unusable for drinking and agriculture leading to potential health risks and economic impacts. Above ground, overland flooding and saltwater inundation can result in loss of cropland and forestland along America's coasts, due to soil salinization (reducing crop and tree growth) and marsh migration (frequently or permanently flooded cropland).
Elevated Groundwater: Tied to saltwater intrusion, rising sea levels also cause groundwater to rise. The elevation of groundwater can lead to increased rainfall runoff and compromised underground infrastructure, such as public utilities, septic systems, and structural foundations. Higher groundwater levels can also lead to water during storms being unable to drain away from homes and businesses.
Landscape Change: Elevated groundwater, along with increased flooding and erosion, will drive a reshaping of U.S. coasts. Beaches and tidal wetlands, some of the environments at greatest risk, may move inland if space is available or they will disappear underwater. Flexibility of the landscape is tied to human development along the coastline. This development can limit where environments can move, or they can provide restoration opportunities expanding coastal environments.
Infrastructure Damage: Sea level rise threatens vital infrastructure that moves people and goods, powers homes and businesses, and delivers public services. Infrastructure along the coast such as roads, bridges, sewage systems, and power plants may be damaged due to flooding, coastal erosion, and saltwater intrusion, leading to significant economic costs, disruptions to daily life, and health risks.
Health Risks: Flooding and infrastructure damage can lead to public health risks, including exposure to contaminated water and the spread of waterborne diseases. Flooding can also increase risk for mold in homes. Water and electricity outages due to infrastructure damage or failure can also delay or deprive residents’ access to refrigerated medication, medical devices, clean drinking water, air conditioning or heat, and delay or prevent medical treatments.
Economic Impacts: Impacts from worsening coastal hazards can ripple across many economic sectors. Local economies, particularly those that rely on coastal and marine activities such as tourism, fishing, and shipping, may suffer from a change in the availability of resources and potential damage to port infrastructure. Additionally, more frequent or worse coastal hazards can alter the insurance market, impacting home and business owners.
Social and Cultural Impacts: The impacts of sea level rise are not the same for everyone. Differences in economic and educational opportunities, infrastructure quality, and investments in flood protection all contribute to varied experiences of impacts for coastal residents, with some communities, often those at a lower income level, at higher risk. Additionally, for cultures that have deep ties to the ocean, mounting changes could result in the loss of cultural practices and heritage sites.
Loss of Habitats: Coastal and marine ecosystems, which provide vital services such as storm protection, biodiversity, and fisheries, can be degraded or lost entirely. Saltwater reaching further inland can expose coastal plants to high amounts of salt, which can damage or kill non-salt tolerant plants. This causes a ripple effect, influencing the entire ecosystem. Some ecosystems have an ability to adapt and migrate inland, but are limited by human development and how quickly changes in sea level are happening.
Adapted from Sea Level 101 on earth.gov (U.S. Sea Level Change, a coordinated effort of NASA, NOAA and partner agencies). Figures and videos are credited in their captions.