How Sea Level Changes Affect Coastal Planning

Rising global sea level is one of the most commonly cited consequences of climate change, but it is often unclear how it might affect people living on the coasts. From the federal government down to the local coastal homeowner, people are asking, “Where is sea level going to be in relation to my beach, my house, or my street?” 

What is the Difference Between Global and Local Sea-Level Rise?

Storm surge on a Louisiana highway.

Storm surge on a Louisiana highway shows the affects of rising sea levels.

High resolution (Credit: NOAA)

Global sea-level rise is a change in the global average sea level due to more water in the world’s oceans. Local sea level, known as relative sea-level change, includes both global sea-level rise and changes in the land elevation.

For example, the 2007 Intergovernmental Panel Report on Climate Change (IPCC) shows the global sea-level rise to be 1.7 to 1.8 millimeters per year (mm/yr) for the past century. But local NOAA measurements show the sea level is rising almost 10 mm/yr in Louisiana because the land is sinking (also known as subsidence). In other coastal areas, seal-level trends are falling. For example, in southeast Alaska, local sea-level trends are falling up to 17 mm/yr because the land is rising.

San Francisco tide station.

The NOAA San Francisco Tide Station, in operation for more than 150 years.

High resolution (Credit: NOAA)

How NOAA is Monitoring Sea Levels

Local communities are growing more concerned about the affects of sea-level rise with global warming. To assess local sea-level rise, the NOAA Center for Operational Oceanographic Products and Services maintains a National Water Level Observation Network of 200 stations throughout the United States. Using at least 30 years of data from 117 of these locations, NOAA analysts calculate relative sea-level trends. The relative sea-level trends for about half of these stations are above 2 mm/yr, which is above the IPCC current global sea-level rise estimates.

“Global sea level acceleration is important for understanding climate change. But it’s the local sea level changes, which will affect coastal structures and the natural environment, that drive local planning and response,” said Mike Szabados, Director of the NOAA Center for Operational Oceanographic Products and Services. 

Planning for the Future

Sea-level trends for regions in the United States.

Sea-level trends for regions in the United States.

High resolution (Credit: NOAA)

Coastal planners, building engineers, as well as the public can refer to their NOAA sea-level stations for information on the local sea level. In addition, NOAA is adding 11 new stations by the end of the year. Armed with this valuable information, communities can decide coastal protection measures and policies and plan accordingly. 

NOAA is increasing efforts to link sea-level measurements to land-measurement systems. This will enable community planners to consider projected sea-level rise estimates when determining the best location for such projects as highways, hospitals, and other public facilities. NOAA will continue to enhance it’s products and services to provide critical information on local and global sea-level trends as we monitor the effects of climate change on our planet. NOAA logo.