Ans) According to given figure,
Total Flow rate(Q) = Flow rate due to pasture(Q1) + Clean straight(Q2) + light brush(Q3) + trees region(Q4)
Using Manning's formula,
Q = A1/N1 R12/3 S1/2 + A2/N2 R22/3 S1/2 + A3/N3 R32/3 S1/2 + A4/N4 R42/3 S1/2
Slope = 0.9 / 1000 = 0.0009
According to given figure,
For y = 2 m
A1 = 2 x 27 = 54 m2
R1 = A1 / P1 = 54 / 29 = 1.862 m
A2 = 2.4 x (2.5 + 2) = 10.8 m2
R2 = A2/P2 = 10.8/(2.5 + 2.4 + 1) = 1.83 m
A3 = (2 +1.5) x 9 = 31.5 m2
R3 = A3/P3 = 31.5/10 = 3.15 m
A4 = 2.5 x 15 = 37.5 m2
R4 = A4/P4 = 37.5/15 = 2.5 m
Manning roughness coefficient for pasture N1 = 0.03 , clean straight = 0.018 , light brush = 0.05 and trees = 0.150
Putting all values,
Q = (54/0.03)(1.862)2/3(0.0009)1/2 + (10.8/0.018)(1.83)2/3(0.0009)1/2 + (31.5/0.05)(3.15)2/3(0.0009)1/2 + (37.5/0.150)(2.5)2/3(0.0009)1/2
Q = 81.74 + 26.93 + 40.62 + 13.82
Q = 163.11 m3/s
For y = 3 m
A1 = 3 x 27 = 81 m2
R1 = A1 / P1 = 81 / 29 = 2.79 m
A2 = 2.4 x (2.5 + 3) = 13.2 m2
R2 = A2/P2 = 13.2/(2.5 + 2.4 + 1) = 2.23 m
A3 = (3+1.5) x 9 = 40.50 m2
R3 = A3/P3 = 40.5/10 = 4.05 m
A4 = 3.5 x 15 = 52.5 m2
R4 = A4/P4 = 52.5/15 = 3.5 m
Q = (81/0.03)(2.79)2/3(0.0009)1/2 + (13.2/0.018)(2.23)2/3(0.0009)1/2 + (40.5/0.05)(4.05)2/3(0.0009)1/2 + (52.5/0.150)(3.5)2/3(0.0009)1/2
Q = 160.50 + 37.56 + 61.77 + 24.21
Q = 284.04 m3/s
1) (20 pts) The cross-section of a creek valley is shown in Figure. Find the flowrate for y-2m and y-3m. The slope...
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