Enter the runoff, drainage area, rainfall intensity, and runoff coefficient values into the calculator, leaving exactly one field empty, to compute the missing parameter.
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Storm Water Runoff Formula
The following equation is used to calculate the Storm Water Runoff.
Q = C * I * A
- Where Q is the Storm Water Runoff (cfs)
- C is the Runoff Coefficient (dimensionless)
- I is the Rainfall Intensity (in/hr)
- A is the Drainage Area (acres)
To calculate the storm water runoff, multiply the runoff coefficient, rainfall intensity, and drainage area.
What is a Storm Water Runoff?
Definition:
Storm water runoff typically refers to the volume of water that flows over a ground surface when rainfall exceeds the soil’s infiltration capacity, and it is critical for assessing flood risks and designing effective drainage systems.
How to Calculate Storm Water Runoff?
Example Problem:
The following example outlines the steps and information needed to calculate the Storm Water Runoff.
First, determine the drainage area. In this example, the drainage area is 50 acres.
Next, determine the rainfall intensity. Assume the rainfall intensity is 2 in/hr.
Then, select the runoff coefficient. For this example, we use a runoff coefficient of 0.45.
Finally, calculate the storm water runoff using the formula above:
Q = C * I * A
Q = 0.45 * 2 * 50
Q = 45 cfs
FAQ
What factors influence storm water runoff?
Several factors such as rainfall intensity, land slope, soil composition, and vegetation cover affect storm water runoff; urbanization and impervious surfaces also play a significant role.
How can storm water runoff be reduced?
Storm water runoff can be reduced by implementing green infrastructure solutions like permeable pavements, rain gardens, and retention basins, which help increase water infiltration and decrease peak flows.
Why is calculating storm water runoff important?
Calculating storm water runoff is crucial for designing efficient drainage systems, managing flood risks, and ensuring sustainable development in both urban and rural areas.