8239

• UCREFRP Catalog Number: 8239
• Author: McAda, C. and K. Fenton.
• Title: Relationship of Fish Habitat to River Flow in the Gunnison River.
• USFW Year: 1998.
• USFW - Doc Type: Project number 47,
• Copyright Material: NO

study sites was broken into 11 habitat categories -fast run, slow run, rapid, riffle,
eddy, pool, slack water, backwater, flooded vegetation, sheet flow, and flooded
bottomland (Table A-1; modified slightly from Osmundson et al. 1995). All available.
habitats were sketched on video prints from earlier flights at similar flows. Mapping
was usually done from a boat moving through the study area, but occasionally was
done from a prominent point on the shoreline with a good view of the river.
Complete maps of the main river channel were made on all occasions. However, the
extensive floodplain at Escalante SWA was impossible to map completely at high
discharges because the water covered a large area that could not be covered in the
boat or on foot and could not be seen from a prominent point on the bank. General
outlines of the flooded area were sketched in the field and then filled in more
completely using the video from that day. The more general habitat types such as
sheet flow and flooded bottomland were used in those cases.
After the flight was completed, videotapes were sent to the laboratory where
overlapping frames of each study reach were digitized (`grabbed') using PC-based
image processing software (TNT Mips version 5.3; Microimages, Inc, Lincoln, NE).
High resolution color prints were made of the digitized frames and sent to the senior
author. Field maps were transferred to the color prints taken on the day (t 1) of
mapping. Habitat boundaries were drawn on the final maps as they were sketched
in the field. Adjustments to habitat boundaries were made when those boundaries
were clearly evident on the new prints. Boundaries of flooded areas outside the
main channel were further delineated with the help of the current video print.
Completed maps were then sent to the junior author for further analysis.
In the laboratory, the individual frames for each site were tied together into one
large mosaic of the reach. The mosaics for each site were set to a common scale by
scanning a 1:12,000 scale color infrared (cir) photograph into the computer using a
Howtek Scanmaster three-color scanner (300 dpi). Once in digital form, the scale of
the scanned photo was set at 1:12,000. Each video mosaic was then displayed on
the computer screen beside the scanned cir photo and common landmarks (e.g.,
prominent trees, rocks, bridges, etc) between the two images were tagged and
saved. A minimum of 20 points distributed throughout the image were selected in
this process. Each control point was then given an exact georeference position
which equalized the scale for the different video flights. After all the video mosaics
were transformed to the same scale, habitat- boundaries from the field maps were
digitized as a vector overlay to the transformed video mosaic. Digitized habitat maps
were carefully reproduced and compared with field maps and live videotape for
accuracy. Surface area for each habitat type was calculated by summing area within
the polygons delineating the 11 habitat categories.
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