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irregular way as discharge increases over this range. At baseflow the water-surface width <br />averages 54 m (Fig. 22a), which is less than half the average bankfull width. At this flow the <br />wetted area of the channel is 40,000 m2 (Fig. 22b) and more than half of the channel perimeter <br />is dry. Flow stays within the baseflow channel until the discharge reaches approximately 140 <br />m3/s (5000 cfs), at which point, the flow begins to inundate bar surfaces, causing a rapid <br />increase in the water surface width and wetted area of the channel (Fig. 22a, b). The width and <br />wetted area increase slowly thereafter; most of the channel is inundated once the flow reaches <br />140 ° <br />E A e 9 8 ° <br />" 120 0 ® 0 0 0 0 <br />r <br />a <br />° <br />° <br />0 <br />3 100 e • 8 8 8 8 <br /> <br />m <br />• 0 <br />tl <br />80 <br />° 0 0 0 0 <br /> <br />rn 0 8 <br />e 0 <br />0 ° <br />0 <br />60 <br />® <br />0 <br />0 <br />W <br />3 <br /> <br />40 0 <br />° <br />0 100 200 300 400 5 00 <br /> Discharge (m3/ s ) <br />_ 100 <br />a? 90 B 4® <br />° 80 • <br />!6 • <br />` 70 <br />a <br />m 60 <br />w <br />3 50 <br />U) <br />m 40 <br />m <br />30 <br />0 100 200 300 400 500 <br />Discharge (m31 s ) <br />Figure 22. Changes in water surface width (a) and wetted area (b) with discharge, RM 176. <br />47