Humboldt Bay, California Benthic Habitats 2009 Substrate

Humboldt Bay is the largest estuary in California north of San Francisco Bay and represents a significant resource for the

north coast region. Beginning in 2007 the Office for Coastal Management began collaborating with the California SeaGrant program and

other local partners to support an ecosystem-based management (EBM) project for Humboldt Bay. One element of this project was to

develop subtidal habitat goals for the long-term management of the bay and provide a framework for conservation and management across

the land-sea interface. The imagery collection and benthic habitat delineation for Humboldt Bay were essential to the development of

subtidal goals and implementation of EBM for the region. Together, these efforts will provide important and replicable data and an

information framework for ecosystem-based coastal and marine conservation planning and implementation. 12 Bit 4 Band imagery was

collected in June,2009 within 1 hour of either side of a minus one (-1) foot tide with low turbidity,low wind,low sun angle and no cloud cover. The horizontal spatial accuracy of the imagery is within +/- 3 meters CE95 of position on the ground and was captured at a spatial resolution (pixel size) of 0.54m x 0.54m. The imagery was tiled and named according to the existing USGS digital ortho quarter quad boundaries (ex. Arcata_South_NE.tif). A small buffer (~100 m) was produced with each tile to prevent gaps in coverage. Habitat features were interpreted and digitized on screen in an ARCGIS Geodatabase 9.3 resulting in accurate and efficient 3D extraction of the data. Habitats were delineated with a high level of detail with the minimum mapping unit (MMU) being 0.01 hectares(approx.10m x 10m).

Original contact information:

Contact Org: NOAA Office for Coastal Management

Phone: 843-740-1202

Email: coastal.info@noaa.gov

The data was developed to support ecosystem based management in the Humboldt Bay region. The focus of the mapping was on shallow water benthic habitats with particular concern for eelgrass meadows.

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The study area covers Arcata (North) Bay, Entrance Bay, South Bay and the Eel River Delta, Humboldt County, California.

NOAA provides no warranty, nor accepts any liability occurring from any incomplete, incorrect, or misleading data, or from any incorrect, incomplete, or misleading use of the data. It is the responsibility of the user to determine whether or not the data is suitable for the intended purpose.

Data is available upon request

None

Polygon labels and boundaries were visually inspected for delineation precision and attribute accuracy. Thematic accuracy assessment methods: The thematic accuracy of the benthic habitat data set was assessed in two phases. The first phase took place in between September 14 and 18 2009, in the same season as image acquisition but prior to any mapping having been completed. A total of 128 points were visited on this trip. The points were selected manually to ensure that both representative habitats visible in the imagery as well as areas of potential confusion. The second phase also involved field visits which took place in May 10 through 13 2010. A total of 24 points were manually selected and visited after reviewing the draft habitat map. Navigation to each field point is accomplished using the source imagery as a backdrop, a real time Wide Area Augmentation System (WAAS) enabled GPS (Garmin 76 unit), and a ruggedized field lap top PC . The PC displays the image of the area with each "target" point as well as a real time symbol display of the boat location via the GPS. This system allows navigation precisely to the "target" point. In shallow or extremely clear water or during low tides when the bottom was exposed direct observations were made from the boat. In deeper areas or areas of unclear water a towed underwater video camera with live feed to a monitor on the boat was deployed. The camera was towed long enough (~2-4 minutes) at each station to provide a complete assessment of the dominate habitat type. The "field" classes were recorded to at least the two digit SCHEME classification level and where possible to the three digit level. The field points were sorted by habitat subclass and additional points were selected through a stratified random sampling process to generate a total of 50 points per class which would support a statistically valid accuracy assessment. These points were visually interpreted by viewing the source imagery. A total of 132 points were analyzed in this way. All the points were assembled into an error matrix where the "field" classification is compared to the "map" classification of each point by category. The resulting accuracy for the Humboldt Bay benthic habitat data at the 2 digit SCHEME classification code level is 84% with a kappa coefficient of 0.793.

The positional accuracy of this data meets USGS NMAS for 1:12000 scale maps. Horizontal accuracy of the data corresponds to the positional accuracy of the aerotriangulated photography that was controlled by GPS survey control points.

Cloud Cover: 0

Minimum mapping unit for habitat polygons was 10 square meters. The study area boundaries for the project were defined by NOAA. Benthic habitat features were captured and classified according to the rules, conventions, and descriptions in the Statement of Work.

Polygon topology present. All polygons were tested for slivers. Every polygon has a label, there are no multiple labels within polygons, there are no contiguous polygons.