From NH Fish and Game: The staff at the Great Bay National Estuarine Research Reserve in Greenland, NH, working in partnership with the National Oceanographic and Atmospheric Administration Office for Coastal Management are mapping the Great Bay in a new way. Experts flew drones over the marsh recently to obtain high-resolution elevation data of the landscape. The information gathered will be used to assess areas for restoration, to serve as a baseline for changes over time, and can be easily entered into models that predict the marshes’ future. GBNERR was designated to be a place to study long-term trends in the estuary including both physical trends, such as water chemistry, and biological fluctuations.
Elevation data were traditionally collected manually with hundreds of individual points using a survey-grade GPS unit. This spring’s survey involved a miniaturized lidar (which stands for light detection and ranging) system to scan the marshes and adjacent forests. Lidar is a remote sensing technology that employs laser pulses to determine precise elevations of target features, such as the ground, trees, and buildings. The lidar-equipped drone remotely acquires precise elevation data in a fraction of the time with minimal impact on the environment. Improved data collection will allow scientists to develop highly detailed, very accurate digital elevation models using millions of points.
“Utilizing drones equipped with lidar, we’re able to create high-accuracy elevation maps based off of millions of data points for four of our key marshes in Great Bay, which we combine with data on the vegetation, water level, and sedimentation on the marsh to allow us to better understand if these valued habitats are able to keep pace with rising sea levels or if they will ‘drown’,” said Christopher Peter, Research Coordinator at Great Bay.
Saltmarshes provide a critical habitat for coastal birds and fish, mitigate flooding, and filter nutrients. Elevation is crucial to a saltmarsh’s survival. If an area is too low and wet, the marsh will drown. If the land is too high and dry, the unique marsh vegetation cannot grow there. Having accurate elevation values on a broad scale supports a variety of mapping and modeling applications to support saltmarsh protection and restoration. Improved data will help Great Bay staff identify key places to focus research and monitoring efforts and recommend management actions that are scientifically more likely to succeed. GBNERR scientists are currently studying the relationship between flooding and specific plant tolerances both at Great Bay and at the other three New England NERRs to regionally understand the impact of rising water levels due to climate change.