2011 Klawock Lagoon, Alaska Imagery and Benthic Habitats

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 Coastal Services Center 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 did not have sufficient biomass 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 accuracy assessment was conducted.

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.

Digital Imagery

Not applicable

Users must assume responsibility to determine the usability of these data.

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Windows NT/2000 Systems, GPro/LPS, Leica ORIMA

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.

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.