Integrating Spatial Infrastructure Components for Measuring “True” Local Sea Level Rise

Deciphering natural and anthropogenic factors contributing to land subsidence in coastal lowlands requires a consistent, accurate, and reliable spatial reference frame upon which observations may be compared over time. Within the National Oceanic and Atmospheric Administration (NOAA), National Geodetic Survey (NGS) has the responsibility to define, maintain and provide access to the U.S. National Spatial Reference System (NSRS) to meet the nation's economic, social and environmental needs. The NSRS and NOAA observing systems provide a foundation upon which localized studies of subsidence can take place and give a more accurate measure of “true” local relative sea level rise that is required for climate change adaptation and mitigation strategies.

The critical aspect of the NSRS for subsidence monitoring is the vertical datum by which heights are defined and related to local water levels. Height Modernization is a NOAA program that combines recent advances in Global Navigation Satellite System (GNSS) technology, with traditional surveying techniques to update the vertical component of the NSRS. NOAA conducts Height Modernization efforts throughout the country to improve coastal and inland elevations and provide essential infrastructure that supports commerce and enhances community resilience. One of the important uses of Height Modernization in coastal areas is to measure rates of subsidence which influence local rates of relative sea level rise.

NGS works with other NOAA offices to tie long-term tide stations and Surface Elevation Tables (SETs) to geodetic infrastructure and provide integrated data on the changing land-water interface. This data is being applied to coastal issues such as sea level rise, habitat restoration, storm surge modeling, and hazard preparedness and response. Understanding the magnitude of local land movement and water level changes can inform development policy, permitting processes, and coastal restoration activities, which in turn can increase the resilience of coastal communities in the face of coastal hazards.