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A landscaped garden with irregular profile and minor undulations, measuring 35,000 sqm, has a total surface area covered with 20% brick paving, 15% cement concrete paving, and rest with grass. The peak intensity of rainfall in that region is 70 mm/hr. The coefficient of runoff for brick paving, cement concrete paving and grass is 0.8, 0.9 and 0.5 respectively. The estimated quantity of runoff in cubic meter/hr for the entire garden area is _____________
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- 1110 to 1430
- 1510 to 1530
- 510 to 530
- None of the above
Correct Option: B
Brick paving area = 20% of 35000 = 7000 m2
Concrete paving area = 15% of 35000 = 5250 m2
Grass cover area = 65% of 35000 = 22750 m2
Water runoff by brick paving = 0.8 × 7000 m2 area × 0.07 m of rain fall = 392.0 m3
Water runoff by concrete paving = 0.9 ×5250 m2 area x 0.07 m of rain fall = 330.75 m3
Water runoff by grass cover = 0.5 × 22750 m2 area × 0.07 m of rain fall = 796.25 m3
