About Ecosystem and Climate Operations (ECO)

NOAA's National Geodetic Survey (NGS) defines, maintains and provides access to the National Spatial Reference System (NSRS) to meet our nation's economic, social, and environmental needs. In fulfilling this mission, NGS has always supported a wide range of activities including mapping and charting, navigation, flood risk determination, and transportation.

However, it has become apparent that there is also an important role for NGS products and services in supporting coastal community resilience, ecosystem services, and ecological integrity, especially in responding to climate change. The NGS Ecosystem and Climate Operations (ECO) Program adapts geodetic survey technologies, instrumentation, and procedures to meet the needs of these new user communities.

Learn more about the collaborative research and projects, the importance of marsh elevation, and the application of surface elevation tables (SETs) below. You can also read the ECO fact sheet and Sentinel Site fact sheet.

Collaborative Research and Projects

Through the ECO team, NGS partners with other NOAA offices, Federal agencies, state and local governments, and nonprofit organizations to focus on non-navigational uses of geospatial data. One primary NOAA partner office is the Center for Oceanographic Products and Services (CO-OPS), whose Coastal Oceanographic Applications and Services of Tides And Lakes (COASTAL) Program focuses on non-navigation services supported by water-level and datum information.

ECO also has long-standing collaborative relationships with NOAA's Office of Coast Survey (OCS) and the National Estuarine Research Reserve System (NERRS). Additionally ECO partners regularly with other Federal agencies including the U.S. Fish and Wildlife Service, U.S. Geological Survey, and U.S. National Park Service.

Importance of Marsh Elevation

The lives of people in coastal communities are intimately linked with coastal salt marshes along the shorelines. These marshes provide nursery habitat for many commercial fishery species, help to buffer storm surges, and remove pollutants from the water, as well as draw tourists in for recreational hunting and fishing. For life in these marshes, elevation is everything. As the tides pulse up and down each day, elevation determines how often the marsh gets flooded and how long it stays wet. This differential wetting and drying drives biogeochemical processes in the soils and creates conditions favoring different vegetation communities in the high and low marsh zones (Earl, Zedler, Cahoon 2011).

As sea levels fluctuate and rise over time, marsh surface elevations also change, together regulating marsh plant species distributions and the vulnerability of the marsh to fragmentation and loss. In large flat coastal plains, small variations in elevations and water levels can alter inundation patterns and affect marsh vigor over vast areas. Marshes that sit higher up in the tidal frame, where the marsh plain is significantly above mean sea level are said to have more "elevation capital" than marshes where the marsh plain is at or just slightly above local mean sea level (Cahoon 2006). While marsh systems have an ability to build elevation and keep the marsh plain above rising seas by trapping sediment and accumulating plant biomass, those with more "elevation capital" are less vulnerable to rising seas or storm surge in the long run than those that sit low in the tidal frame.

The vulnerability of marsh systems to storm surges and accelerating sea level rise can threaten the services they provide coastal communities. As a result, better characterizing this vulnerability is worth billions of dollars and affects the lives of hundreds of millions of coastal residents around the world. It is this relevance to people's lives and livelihoods which makes measuring trends in marsh surface elevations an important topic for research.

Surface Elevation Tables (SETs)

To most accurately measure marsh elevations and how they are changing in relation to local sea levels over time, scientists have been using Surface Elevation Tables (SETs) in increasing numbers around the world for the past 20 years or more (Bouman, Cahoon 2002). SETs consist of a "stable" monument driven into the marsh upon which the SET instrument is placed. The monument and instrument fit together in only one way so that the position and orientation of the instrument is consistent each time measurements are taken and any changes in the readings can be attributed to changes of the marsh surface.

At first, rates of change were referenced to the monument itself, and each SET's trajectory was relative only to that monument. Over the past several years, researchers have begun in earnest to survey their SET monuments so that the measured trajectories can now be related to a common vertical datum, either a geodetic datum such as NAVD88 or to local tidal datums by surveying the SETs in to nearby tidal benchmarks. This ability to directly relate the elevation of the marsh plain to local tidal datums enables the calculation of elevation capital, which is helping give scientists and coastal managers an important spatial context for their study areas and a better understanding of the vulnerability of different marsh systems.

Recent advances in SET design have reduced some instrument error and enabled integration with GPS receivers; as a result precise ellipsoid heights can be established for the SET benchmarks and then consistently transferred to the marsh surface (Geoghagen). While SETs are able to provide elevation measurements accurate at the millimeter level, each deployment only samples approximately 1.5 square meters of the marsh surface at a time, requiring extensive SET networks to characterize changes across a marsh system. These SET networks are expensive, difficult to install, and require long term commitment of staff time to physically travel to the sites and manually take measurements.

Works Cited

Boumans, R.M.J. & Day, J.W. "High precision measurements of sediment elevation in shallow coastal areas using a sedimentation-erosion table." Estuaries and Coasts 16, 375-380 (1993).

Cahoon, D.R. et al. "Coastal wetland vulnerability to relative sea-level rise: wetland elevation trends and process controls." Wetlands and Natural Resource Management 271-292 (2006).

Cahoon, D.R., Lynch, J.C., Perez, B.C., Segura, B., Holland,R.D., Stelly, C., Stephenson, G., and Hensel, P. "High-precision measurements of wetland sediment elevation: II. The Rod Surface Elevation Table." Journal of Sedimentary Research 72(5): 734-739 (2002).

Cahoon, D.R., Perez, B.C., Segura, B.D. & Lynch, J.C. "Elevation trends and shrink-swell response of wetland soils to flooding and drying." Estuarine, Coastal and Shelf Science 91, 463-474 (2011).

Earle, J.C. & Kershaw, K.A. "Vegetation patterns in James Bay coastal marshes. III. Salinity and elevation as factors influencing plant zonations." Canadian Journal of Botany 67, 2967-2974 (1989).

Geoghagen, C.E., Breidenbach, S.E., Lokken, D.R., Fancher, K.L., Hensel, P.F., "Procedures for Connecting SET Bench Marks to the NSRS." NOAA Technical Report NOS NGS-61 (2010).

Zedler, J.B. et al. "Californian Salt-Marsh Vegetation: An Improved Model of Spatial Pattern. Ecosystems 2, 19-35 (1999).