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Runoff Volume Formula:
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Runoff volume calculation estimates the amount of water that will flow off a surface during a rainfall event. This is important for stormwater management, drainage design, and environmental planning.
The calculator uses the runoff volume formula:
Where:
Explanation: The equation calculates the volume of water that runs off a surface rather than being absorbed, converted to gallons for practical applications.
Details: Accurate runoff volume estimation is crucial for designing effective drainage systems, preventing flooding, managing stormwater, and complying with environmental regulations.
Tips: Enter rainfall depth in feet, surface area in square feet, and the appropriate runoff coefficient (typically 0.05-0.95). All values must be positive numbers.
Q1: What is a runoff coefficient?
A: A decimal value between 0 and 1 that represents the fraction of rainfall that becomes surface runoff. It varies by surface type (e.g., pavement: 0.8-0.95, grass: 0.05-0.35).
Q2: Why convert to gallons?
A: Gallons are a common unit for water volume measurement in many practical applications, especially in the United States.
Q3: How accurate is this calculation?
A: It provides a reasonable estimate for planning purposes but actual runoff may vary based on soil saturation, rainfall intensity, and other factors.
Q4: Can I use inches for rainfall and still get gallons?
A: Yes, but you would need to convert inches to feet (divide by 12) before entering the value, or modify the formula accordingly.
Q5: What are typical runoff coefficients for different surfaces?
A: Asphalt/concrete: 0.8-0.95, gravel: 0.3-0.7, lawn (sandy soil): 0.05-0.2, lawn (clay soil): 0.2-0.35, forest: 0.01-0.2.