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<br />3 <br /> <br />October 16 and September 28. In addition, the backwater data from this <br />study can be compared with backwater data from previous studies at similar <br />flows. <br /> <br />The airborne video was acquired at each site with an Ikigami video camera <br />which was attached to the front of a helicopter on a Tyler mount. The <br />camera was connected to a monitor viewed by a flight scientist in the <br />helicopter. This allowed the flight scientist and helicopter pilot to <br />maintain the river in the center of the video image. The flight scientist <br />also annotated the video tape with audio information about backwaters, side <br />channels, general water turbidity, and weather conditions as they appeared <br />visually from the helicopter. This function served as a "ground truthing" <br />effort which assisted the video interpreter in identifying river features on <br />the video monitor in the laboratory. <br /> <br />The video images were analyzed on a 386-microcomputer system which included <br />a video capture board, and a color monitor. Analysis was performed with <br />Map and Image Processing System (MIPS) software. Video images were viewed <br />on the color monitor and captured when backwater habitat was identified. <br />The video image was viewed repeatedly until the MIPS operator was confident <br />if backwaters were present and what their boundaries were. The audio <br />portion of the tape was listened to at this time to facilitate the process. <br />Scale was calculated with ground panels, constructed at specified distances <br />200 feet apart, from white, plastic paper which was visible on the video <br />image. Ground panels were placed at each site. <br /> <br />Backwaters outlines were traced on the video monitor using a cursor <br />controlled by a mouse and creating short line segments on the image. <br />Backwater area and number were calculated by MIPS software and recorded for <br />each flow for each site. <br /> <br />Results <br /> <br />Island Park <br /> <br />Data summarizations of backwater habitat for 1989 are presented in <br />tables 1-3. Total backwater area at the Island Park site on August 2 <br />(flow = 1,515 ft3/s) was 15,682 m2 or 2,614 m2/mile (table 1). There was a <br />total of 26 backwaters. Following fluctuation of flows between 1,600 and <br />2,900 ft3/s, backwater area decreased 30 percent to 10,993 m2, and backwater <br />numbers decreased by about 15 percent, to 22 on August 16. Stabilized flows <br />at about 1,000 ft3/s for 6 weeks had little effect on backwater habitat. <br />There were 25 backwaters with a total area of 10,946 m2 on September 28 <br />(flow = 1,420 ft3/s). <br /> <br />The higher flows on October 11 (approximately 1,900 ft3/s) produced the <br />fewest backwaters (20) and least backwater area (8,614 m2). It is not known <br />if the decrease in backwater habitat was related to the antecedent <br />fluctuating flows, or the substantially higher flows on this date. <br />