Sea Level Rise

Global sea level is rising because of climate change. Increasing temperatures cause sea level to rise due to 1) thermal expansion as the ocean water takes up more space as it becomes warmer and 2) the melting of ice sitting on land, such as mountain glaciers and polar ice sheets. The rate of global sea level rise is accelerating, and it will continue to increase as the climate continues to warm.

Relative, or local, sea level rise is an increase in mean sea level relative to a point on land. Maryland is experiencing higher rates of relative sea level rise than the global average due to several factors, including Maryland’s geographic position in relation to melting polar ice sheets and land subsidence. During the last ice age, glaciers covered the northeastern United States and the weight of the ice pushing down caused the Earth’s crust outside the ice sheet to bulge up. This ice sheet has now melted, but the crust is still returning to its original position, causing our region to slowly sink, or subside. This subsidence causes relative sea level in Maryland to rise at a higher rate than the global average, but most of the relative sea level rise we see is still due to climate-driven global processes.

Nuisance Tidal Flooding

Rising seas already cause recurrent high tide flooding, also known as nuisance flooding or sunny day flooding, in some low-lying coastal areas in Maryland. This problem is expected to worsen into the future as sea levels continue to rise. For example, the NOAA tide gauge in Baltimore experienced 11 days of high tide flooding in 2019, and is projected to experience 50-155 days of high tide flooding in 2050. You can assist with documenting nuisance flooding in your neighborhood by uploading photos to the MyCoast: Maryland platform.

Image of flooding in Annapolis Harbor
Annapolis Harbor
Image of flooding at Baltimore's Inner Harbor
Baltimore Inner Harbor
Image of nuisance flooding in Denton, MD
Denton, MD
Image of nuisance flooding in Ocean City, MD
Ocean City, MD

Sea Level Rise Projections

Scientific projections of sea level rise can inform projects and decisions to help increase resilience. In 2018, the University of Maryland Center for Environmental Science (UMCES) produced a report with updated sea level rise projections for the state of Maryland. For information on incorporating these sea level rise projections into projects, refer to Guidance for Using Maryland’s 2018 Sea Level Rise Projections. This guide was created by University of Maryland Sea Grant Extension and Maryland Department of Natural Resources staff and walks users through a step-by-step process for selecting sea level rise estimates to use in projects. This approach can be applied to any planning, regulatory, or site-specific project in Maryland at the private, local, state, or federal level that needs to consider sea level rise impacts.

image of 2023 Sea Level Rise report cover
Cover image of Sea Level Rise Guidance document

Visualizing Sea Level Rise

Online tools, such as the NOAA Sea Level Rise Viewer, can help visualize the impacts of future sea level rise. These tools allow users to adjust the water level 0-10 feet above the average high tide line and view a map showing areas that may be impacted by coastal flooding. In Maryland, sea level is expected to rise approximately 1-2 feet by 2050 (above Year 2000 levels) and may exceed 4 or more feet by 2100. Understanding which areas may be inundated due to sea level rise in the coming decades can help inform decisions made today about land use and coastal development.

 

Video tutorial on using the NOAA Sea Level Rise Viewer to visualize future flooding from rising seas.

Other Impacts of Sea Level Rise

In addition to chronic inundation, sea level rise can have have several other impacts on coastal resources and communities:

  • Erosion: Higher sea levels can cause coastal erosion to accelerate because waves are able to reach higher elevations. 
  • Storm surge: Storm surge is the water pushed onto land by wind from a coastal storm. As sea level rises, storm surges are becoming higher and can cause more damage.
  • Stormwater management: Higher sea levels can prevent stormwater management systems from functioning and cause increased flooding when there is precipitation.
  • Rising groundwater: Rising seas can also cause groundwater levels to rise, potentially leading to increased flooding and septic system failure in low-lying coastal areas.
  • Saltwater intrusion: As sea levels rise, saltwater can move onto land and infiltrate freshwater aquifers. Saltwater intrusion can affect coastal agriculture, forests, and water resources. 

Adapting to Sea Level Rise

Coastal communities in Maryland are adapting to rising seas by considering sea level rise in long range plans and infrastructure siting, preserving land to allow inland migration of marsh habitat, elevating roads and enhancing stormwater management systems, and many other activities. Sea level rise is a complex issue, and there is not a one-size-fits-all solution. Contact us to discuss potential sea level rise adaptation options for your community.

Tools and Resources

General

NOAA Sea Level Trends

NOAA Climate Change: Global Sea Level

Nuisance Tidal Flooding

NOAA State of High Tide Flooding and Annual Outlook -- High tide flooding trends and projections for NOAA tide stations

MyCoast: Maryland -- Online portal to collect photos of nuisance tidal flooding and precipitation-caused flooding in Maryland

Sea Level Rise Projections

Sea-Level Rise Projections for Maryland 2023

Visualizing Sea Level Rise

NOAA Sea Level Rise Viewer