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Measuring Cross-Sectional Area

The simplest approach to measuring cross-sectional area is to locate a number of points on the stream bottom by measuring down from the tagline (or yardstick) at regular intervals (see ``$d_i$'' in Fig. 3.2. Then draw these locations (and the water surface) to scale on graph paper, and count the squares to determine the area. A second method is to approximate the area by a series of rectangles, as shown in Fig. 3.2 and Table 3.2, Sanders (1998). If you measure depth at regular intervals (e.g. 2 cm), then the width $b_i$ of each rectangle is constant.

Figure 3.2: Measurement of stream cross-sectional area (after Fig. 3.21, Sanders, 1998).
Image ./sanders-1998_fig3-21.jpg

Figure 3.3: Students gauging Cottonwood Creek, UTD. When creek is ``bankfull'' taglines will be used (as shown), when creek is low, yardsticks will replace the taglines and centimeter rulers will be used to measure depths.
Image ./streamGauging_spring99.jpg

GEOS 3110 Professor's Notes, Summer 2003
Dr. T. Brikowski, UTD