1. What is the Rainwater Flow Equation?

The rainwater flow equation calculates the flow rate of rainwater from a roof surface based on rainfall intensity and collection area. This is essential for proper sizing of drainage systems and gutters.

2. How Does the Calculator Work?

The calculator uses the rainwater flow equation:

Where:

• \( Q \) — Rainwater flow rate (L/s)
• \( i \) — Rainfall intensity (mm/h)
• \( A \) — Collection area (m²)

Explanation: The equation converts rainfall intensity and area into flow rate, with the divisor 360 converting units from mm/h·m² to L/s.

3. Importance of Rainwater Flow Calculation

Details: Accurate rainwater flow calculation is crucial for designing effective drainage systems, preventing water accumulation, and avoiding structural damage to buildings.

4. Using the Calculator

Tips: Enter rainfall intensity in mm/h and collection area in m². Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical rainfall intensity value?
A: Rainfall intensity varies by location and storm event. Common design values range from 50-150 mm/h, but local meteorological data should be consulted for accurate values.

Q2: How do I measure the collection area?
A: The collection area is the horizontal projection of the roof surface that drains to a particular outlet, measured in square meters.

Q3: Why is the result in liters per second?
A: Liters per second is a standard unit for flow rate in drainage engineering and allows for easy sizing of pipes and gutters.

Q4: Does roof slope affect the calculation?
A: The basic equation uses horizontal projection area. For steep slopes, some additional considerations might be needed for very accurate calculations.

Q5: Should I include a safety factor in my design?
A: Yes, it's common practice to include a safety factor of 1.2-1.5 in drainage system design to account for potential underestimation and climate change effects.