Abstract:
The dataset shows the locations where eelgrass was observed within the following waterbodies: Great Bay, the mouth of the Squamscott River, the tidal portion of the Lamprey River, the tidal portion of the Oyster River, the tidal portion of the Bellamy River, the Piscataqua River and Portsmouth Harbor and its associated creeks, and the coastal shore of Odiorne Point. Photointerpretation was completed on unoccupied aerial vehicle (UAV) collected orthophotography, Sentinel satellite imagery, and non-geo-rectified aerial digital photos taken with a downward pointing GoPro camera mounted to the underside of a light airplane. Vertical 2-6 cm spatial resolution UAV imagery was collected between late May through October 2023 over the study area inclusive of RGB, Red-Edge, and Near Infrared bands. Sentinel satellite imagery was collected for the dates of August 22nd, September 4th, and October 4th, 2023, over the study area at a 10 m spatial resolution. The eelgrass habitat mapped from the above listed imagery was verified using the ground truthing data from preselected locations and ad hoc locations chosen during the course of the field work. Ground truthing was done from a small boat during the same season as the photographs were taken. Ground truth observations were made on all tides using a drop camera with video recording capabilities and at low tide when visual observations were recorded. Database file attributes for the 2023 survey are as follows: “id,” a unique consecutive number; “Hectares,” the area of the polygon in hectares; “Acres,” the area of the polygon in acres; “Year,” equal to 2023, the year of the imagery used, “Label” for the assessment zone, and “type” to distinguish between polygons mapped as eelgrass, widgeon grass, or both, “Confidence,” a measure of cartographer confidence (H = Higher, M = Medium, L = Lower) of the existence and/or cover type of vegetation per polygon. “Notes,” a text field listing the types of imagery used and/or mapping limitations per polygon as observed by the cartographer. The items “Confidence” and “Notes” were added to help record varying vegetation mapping confidence levels caused by high turbidity and/or depth clarity issues with this year’s imagery.
Purpose:
The dataset was developed to monitor the distribution of eelgrass within the Great Bay Estuary over time. With the exception of 2018 and 2020, surveys have been completed yearly since 1986 to track trends over time.
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: biota
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: Eelgrass
Theme_Keyword: Estuary
Theme_Keyword: Estuarine
Theme_Keyword: Biology
Theme_Keyword: Ecology
Place:
Place_Keyword_Thesaurus: ISO 19115 Topic Category
Place_Keyword: Oceans
Place_Keyword: Northeast
Place_Keyword: New England
Place_Keyword: New Hampshire
Place_Keyword: Great Bay
Place_Keyword: Little Harbor
Place_Keyword: Piscataqua River
Place_Keyword: Lamprey River
Place_Keyword: Oyster River
Place_Keyword: Bellamy River
Place_Keyword: Portsmouth Harbor
Place_Keyword: Squamscott River
Place_Keyword: New Castle
Place_Keyword: Rye
Place_Keyword: Portsmouth
Place_Keyword: Newington
Place_Keyword: Greenland
Place_Keyword: Stratham
Place_Keyword: Newfields
Place_Keyword: Newmarket
Place_Keyword: Durham
Place_Keyword: Dover
Place_Keyword: Madbury
Place_Keyword: Eliot
Place_Keyword: Kittery
Place_Keyword: Maine
User is required to read metadata completely before using the data. The information provided in this dataset was developed by an independent contractor and used by the NH Department of Environmental Services (NHDES). Development of these databases is an ongoing project; they may not contain all existing and potential sites, stations, or threats. The NHDES is not responsible for the use or interpretation of this information, or for any inaccuracies in the site names or locations. All information is subject to verification. These data are to be used for planning purposes only; distribution is discouraged.