The Hudson River Estuary is home to many aquatic plant species. Those that grow underwater are called submerged aquatic vegetation, shortened to SAV. Beds of SAV create shallow water habitats, which offer refuge and nursery areas for fish, foraging grounds for waterfowl, improve water quality from oxygen production and nutrient uptake, and provide many other ecosystem benefits. Paddlers can enjoy viewing these underwater meadows in shallow areas and within tidal creeks along the Hudson River.
The Hudson River SAV Project is part of a larger effort to research, monitor, and collaborate with volunteers to better our understanding of aquatic habitats in the Hudson River Estuary. The program has three main parts: Aerial Mapping, Long-Term SAV Monitoring, and Volunteer Observations.
The Hudson River SAV Project
Aerial Mapping
The Hudson River National Estuarine Research Reserve, in partnership with the Cornell Institute for Resource Information Sciences (IRIS), has been mapping SAV in the Hudson River and its tributaries since 1997.
The Reserve coordinates periodic aerial mapping to better understand how SAV beds are changing over time. On a clear day at low tide, a plane flies along the river corridor and collects high-resolution photographs from Troy to Hastings-on-Hudson. Specialists from Cornell IRIS carefully interpret the aerial photos and identify areas with native SAV and invasive water chestnut (Trapa natans). These areas are digitized, creating online maps that display important data about SAV acreage and location within the Hudson River Estuary.
Maps generated through the aerial survey are publicly available for anyone to explore via the NYS GIS Clearinghouse. Reserve staff also prepare detailed reports for each survey.
Hudson River SAV Reports
Reserve scientists synthesize findings from each SAV mapping effort and produce a report detailing survey methods, interpretation of aerial photography, and changes in mapped SAV over time.
NYS GIS Clearinghouse MAPS
Two maps are created from each aerial survey. The next aerial mapping survey is expected in 2026.
- SAV Inventory – shows the extent of SAV and water chestnut in a particular mapping year.
- Documented SAV Habitat Map – shows all areas where SAV has been mapped since 1997.
Black and white outline of New York State depicting the survey locations for periodic aerial surveys of SAV in the Hudson River Estuary watershed.
Bed of Water Celery (Vallisneria americana) at Stockport Creek.
Long-Term SAV Monitoring
Since 2011, the Hudson River National Estuarine Research Reserve has conducted annual monitoring of SAV beds at each of the four Reserve component sites.
Data from these in-depth, long-term efforts are publicly available at the NERRS Centralized Data Management Office (CDMO) website via the Vegetation Monitoring App. Data files include both SAV and emergent tidal wetland vegetation data for the Reserve component sites. Data from other participating Research Reserves throughout the country are also available on the CDMO Vegetation Monitoring App. These datasets are publicly accessible for researchers, educators, students, and anyone who may be interested in estuarine vegetation.
For questions about the Reserve’s SAV data, contact the Habitat Researcher at Christina.Pacella@nulldec.ny.gov.
National Estuarine Vegetation Data
The National Estuarine Research Reserve System has developed a consistent protocol for monitoring vegetation across the nation’s estuaries. To date, 18 Reserves have implemented this vegetation monitoring protocol. Available data types include SAV, marsh vegetation, and mangroves.
Volunteer Observations
Volunteer paddlers and aquatic habitat enthusiasts have collected observational data on Hudson River SAV since the early 2000s. Volunteers record information on species presence/absence, plant cover, water depth, and other environmental conditions. Historically managed by the Cary Institute of Ecosystem Studies, the volunteer program is now part of the Hudson River National Estuarine Research Reserve.
Two volunteer meetings are held annually. The spring meeting digs into findings from the previous season’s data and briefs volunteers on other SAV updates. A summer on-the-water training introduces newcomers to the program and teaches data collection protocols.
All are welcome to contribute SAV observations while in/around the Hudson River and its tributaries. Contact HudsonRiverSAV@nulldec.ny.gov to get started.
Resources for Volunteer Monitors
Volunteer Handbook
Field Guide to Aquatic Plants of the Northeast
Have You Seen SAV? Submit Your Observations
The volunteer monitoring program accepts observations from the entire tidal portion of the Hudson River (from the federal dam in Troy to New York Harbor) and in tidal creeks and streams along the Hudson River. If you aren’t sure where to look, check out the Research Reserve’s SAV maps.
Submit your SAV sightings through the digital form below, or open the submission form in a new window.
