Storm Water Drainage Calculator
Calculate storm water runoff and required pipe diameter for drainage systems
About this calculator
The Storm Water Drainage Calculator helps engineers, contractors, and property developers determine proper drainage system requirements for managing rainwater runoff. This essential tool calculates both the expected stormwater volume based on rainfall intensity and catchment area, and determines the appropriate pipe diameter needed to handle the flow efficiently. Accurate drainage calculations are crucial for preventing flooding, property damage, and ensuring compliance with local building codes and environmental regulations.
How to use
Enter your catchment area, rainfall intensity, and runoff coefficient based on surface type. Input the desired flow velocity and pipe material properties. The calculator will compute the peak runoff rate using the rational method and recommend the minimum pipe diameter required to handle the calculated flow volume safely.
Frequently asked questions
What is the runoff coefficient and how do I choose it?
The runoff coefficient represents how much rainfall becomes surface runoff. Use 0.1-0.3 for grass, 0.4-0.6 for gravel, and 0.7-0.95 for concrete or asphalt surfaces.
How do I determine the rainfall intensity for my area?
Use local meteorological data or building codes which specify design rainfall intensities. Common values range from 25-150 mm/hour depending on climate and design standards.
What pipe materials work best for stormwater drainage?
Concrete, PVC, and HDPE pipes are commonly used. Consider factors like soil conditions, load requirements, and local regulations when selecting pipe material and sizing.