Klawock Lagoon, Alaska Benthic Habitats 2011 Geoform

The Klawock River on Alaska's Prince of Wales Island drains a 29,061 acre watershed with 132 miles of streambed habitat supporting seven salmon and trout species. Traditionally the river and lagoon supported salmon harvests exceeding 30,000 fish annually. The salmon fishery is an important economic factor and food source in the Klawock area. It is also an important cultural resource to local inhabitants. In 1964 a causeway was constructed blocking access to the lagoon from adjacent Klawock Bay. This has resulted in dramatic decreases in salmon harvests. The Nature Conservancy has lead a broad partnership to construct a culvert through the causeway thus re-establishing free passage between the river and Klawock Bay which is expected to help restore a full use of the river as spawning habitat by salmon and generally improve the quality of the lagoon. Benthic habitats in the lagoon and adjacent Klawock Bay and Klawock Harbor were mapped in spring 2011 to establish a baseline of benthic communities in the area with emphasis on eelgrass beds which are essential to the early survival of salmon fry. The habitat map will guide ongoing monitoring activities in the lagoon and form the basis of future change detection efforts.

Aerial multi-spectral imagery was collected over the lagoon, bay, and harbor during the week of April 19, 2011. The mission was timed to coincide with the breaching of the causeway. The environmental considerations important to successful benthic mapping were incorporated into the mission planning. These included, imagery to be collected within 1.5 hours of a zero or negative tide, clear water conditions (no algal blooms, or sediment plumes from runoff), low winds to avoid surface waves, and sufficient solar illumination to image submerged areas. These collection parameters were defined by the Office for Coastal Management prior to collection of the imagery. Despite weather and water conditions which were not ideal, imagery adequate to map most of the habitats in the lagoon was successfully collected on April 19, 2011.

Eelgrass habitats in the Lagoon did not have sufficient biomass or illumination through the water column at the time of the aerial mission to be mapped from that source so eelgrass habitats were determined by two field-digitizing processes, one in August 2010 and one in September 2011. The final hybrid map captures habitats 10m x 10m or larger and has the same positional accuracy as the source imagery.

Field data to guide the mapping was supplied by several project partners. A comparison between the field data and the map shows high levels of agreement, although no traditional quantitative accuracy assessment was conducted.

Original contact information:

Contact Org: NOAA Office for Coastal Management

Phone: 843-740-1202

Email: coastal.info@noaa.gov

The data was developed to establish a baseline of benthic habitats in the lagoon and support future change detection activities. These data contribute to assessing conditions prior to opening of a new culvert between the Klawock River, the lagoon, and Klawock Bay to re-establish salmon use of the Klawock River. 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 Klawock Lagoon, Klawock Harbor, and Klawock Bay, Borough of Juneau, Alaska.

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

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Polygon labels and boundaries were visually inspected for delineation precision and attribute accuracy. In August 2011 a draft habitat map was reviewed by OCM staff and project partners to identify areas of error or confusion. The users did not identify any significant errors in the map. In September, TNC staff visited 59 sites in the bay and lagoon and collected field photography to refine the map and further assess its quality. These field photos were collected at pre-selected sites to confirm conditions on the ground. A hand-held GPS unit was used to ensure that the photo was taken to obtain a coordinate for the photo to ensure successful comparison to the map. In this initial assessment, X of X photos were in agreement with the draft map.

An independent NSSDA spatial accuracy assessment was not performed on the imagery; however, imagery from the GeoScanner system typically produces ortho-rectified products with a spatial accuracy meeting or exceeding +/- 3m of position on the group CE95.

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Minimum mapping unit for habitat polygons was 100 square meters. The study area boundary for the project was defined by TNC. Benthic habitat features were captured and classified according to the rules, conventions, and descriptions in the Statement of Work.

Polygon topology present. Every polygon has a label, there are no multiple labels within polygons, there are no contiguous polygons.