Water: Monitoring & Assessment

# Figure 5.6

## Determining Average Cross-Sectional Area (A) |
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Transect #1 (upstream) |
Transect #2 (downstream) |
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... | Interal width (feet) |
... | Depth (feet) |
... | Interal width (feet) |
... | Depth (feet) |
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A to B | = | 2.0 | 1.0 | (at B) | A to B | = | 2.5 | 1.1 | (at B) | ||||

B to C | = | 2.0 | 0.8 | (at C) | B to C | = | 2.5 | 1.0 | (at C) | ||||

C to D | = | 2.0 | 0.5 | (at D) | C to D | = | 2.5 | 0.4 | (at D) | ||||

D to E | = | 2.0 ---- |
0.0 ---- |
(shoreline) | D to E | = | 2.5 ---- |
0.0 ---- |
(shoreline) | ||||

Totals |
8.0 | 2.3 | 10.0 | 2.5 | |||||||||

Average depth = 2.3/4 = 0.575 feet | Average depth = 2.5/4 = 0.625 feet | ||||||||||||

Cross-sectional area of Transect #1 |
Cross-sectional area of Transect #2 |
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= Total width X Average depth = 8.0 ft X 0.575 = 4.60 ft ^{2} |
= Total width X Average depth = 10.0 ft X 0.625 = 6.25 ft ^{2} |
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Average area = (Cross-sectional area of Transect #1 + Cross-sectional area of Transect #2)/2 |
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= (4.60 ft^{2} + 6.25 ft^{2})/2=5.42 ft ^{2} |
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Figure 5.6A sample calculation of average cross-sectional area |