Eelgrass Extent - Coastal British Columbia

This dataset represents polygons of eelgrass on the BC coast predicted from existing geospatial datasets of seagrass extent (ShoreZone) and bathymetry.

The extent of eelgrass in British Columbia was estimated using a novel tool created for ArcGIS (the Gregrator).This tool requires 2 inputs: (1) the coastline data from Shorezone (including line shapefiles that represent the extent of eelgrass) and (2) bathymetry data. Briefly, each line segment of coast in ShoreZone is converted to points along its vertices. These points are used to generate Thiessen polygons, where each Thiessen polygon “defines an area of influence around its sample point, so that any location inside the polygons is closer to that point than any of the other sample points” (Esri, 2016). Thiessen polygons were then clipped to the extent of polygons which spanned the area from the coastline to maximum depth based on the results of the bathymetry analysis. These methods are based on those described in Gregr et al 2013.

Gregr, E. J., Lessard, J., & Harper, J. (2013). Progress in Oceanography A spatial framework for representing nearshore ecosystems. Progress in Oceanography, 115, 189–201. http://doi.org/10.1016/j.pocean.2013.05.028

Datasets:

  1. Shorezone “ShoreZone” is a habitat classification and mapping method that represents the most complete geographical dataset of geomorphological and biological characteristics of the coastline of the Pacific Northwest including British Columbia (BC), Canada, as well as the states of Washington and Oregon in the USA. The current BC ShoreZone dataset was created from georeferenced video and photographs collected at low tide between the late 1980s and 2004 . These georeferenced images were used to map the linear distribution of biological communities (including eelgrass) along geomorphologically consistent sections of coastline (aka “units”). The data exist in a GIS where presence and absence of eelgrass is recorded as a line along units of shoreline. The ShoreZone dataset used in this analysis was provided by the province of British Columbia and can be requested from DataBC. It can be viewed online at http://maps.gov.bc.ca/ess/sv/crims/ (Internet Explorer required).

  2. Bathymetry Two bathymetry datasets were used to estimate eelgrass extent in coastal BC. Bathymetry data were used to generate a depth contour representing the average maximum depth extent of eelgrass in a given region. (1) The Canadian Hydrographic Service (CHS) digital vector chart data contains bathymetry in a GIS for most of mainland BC and Vancouver Island, excluding Haida Gwaii. The resolution of bathymetry varies regionally along the coast, with higher resolution data available at a 20k - 50k scale and lower resolution available at a 50k - 150k scale. Quality of depth contours within the same data layer also appeared to vary. For example, the Strait of Georgia has higher resolution bathymetric data than the North Coast region despite being from the same data layer, likely a consequence of increased mapping efforts in the Strait of Georgia region due to higher population and shipping traffic. This data was paid for by the Hakai Institute and is not available for distribution. (2) Bathymetry data for Haida Gwaii was provided by Patrick Bartier, Geomatics Coordinator at Parks Canada Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve and Haida Heritage Site. It was provided in a 5 m raster cell format extending 5 km offshore.

Attribute Data:

FID Internal feature number

Feature geometry Coordinates defining the features.

PHYIDENT Unique identifier for each shoreline segment within the ShoreZone dataset.

Coast_ID A 2 letter code describing the geographical region of each ShoreZone segment where: CC = Central Coast, HG = Haida Gwaii, JS = Johnstone Strait, NC = North Coast, SG = Strait of Georgia, VI = Vancouver Island

ZOS This attribute describes each shoreunit where eelgrass is present as either "continuous" (C) or "patchy" (P) where: C = a distribution of "continous" where eelgrass was visible in more than half (50-100%) of the unit's alongshore length. P = a distribution of "patchy" where eelgrass was visible in less than half (approximately 25 - 50%) of the alongshore unit length. Alaska ShoreZone Protocol

Shape_Leng Perimeter of feature in meters. Positive real numbers that are automatically generated.

Shape_Area Area of feature in internal units squared (meters). Positive real numbers that are automatically generated.

Luba Reshitnyk (Hakai Institute), Will McInnes (Hakai Institute), Taylor Denouden (Hakai Institute), Margot Hessing-Lewis (Hakai Institute)

Access and Use

Licence: Appropriate credit must be given to Hakai Institute and the authors of the dataset.

Data and Resources

Dates

Metadata Created October 26, 2018, 22:48 (UTC)
Metadata Updated October 26, 2018, 22:48 (UTC)
Reference Date(s) 2016-09-09 (Creation)
2016-09-09 (Publication)
Frequency of Update
Metadata Date October 17, 2018, 21:44 (UTC)

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Dataset extent

Map data © OpenStreetMap contributors

Additional Info

Field Value
Contact Email data@hakai.org
encoding utf8
metadata-language eng
progress completed
resource-type dataset
Responsible Party Hakai Institute (Point of Contact, Processor)
spatial-reference-system 3005