1. What is Stormwater Capacity?

Stormwater capacity refers to the volume of water that needs to be managed during rainfall events. It's calculated based on the catchment area, rainfall intensity, and the runoff coefficient which represents the portion of rainfall that becomes surface runoff.

2. How Does the Calculator Work?

The calculator uses the stormwater capacity formula:

Where:

• \( V \) — Stormwater capacity (m³)
• \( A \) — Catchment area (m²)
• \( R \) — Rainfall depth (m)
• \( C \) — Runoff coefficient (dimensionless)

Explanation: The formula calculates the volume of stormwater runoff by multiplying the catchment area by the rainfall depth and the runoff coefficient.

3. Importance of Stormwater Capacity Calculation

Details: Accurate stormwater capacity calculation is crucial for designing effective drainage systems, preventing flooding, managing water resources, and meeting regulatory requirements for stormwater management.

4. Using the Calculator

Tips: Enter the catchment area in square meters, rainfall depth in meters, and the appropriate runoff coefficient. The runoff coefficient typically ranges from 0 (no runoff) to 1 (all rainfall becomes runoff), with common values around 0.3-0.9 depending on surface type.

5. Frequently Asked Questions (FAQ)

Q1: What is a runoff coefficient?
A: The runoff coefficient represents the fraction of rainfall that becomes surface runoff rather than being absorbed or evaporated. It varies based on surface type, slope, and soil conditions.

Q2: How do I determine the appropriate runoff coefficient?
A: Runoff coefficients are typically determined from engineering tables based on surface characteristics. For example: paved areas (0.8-0.95), lawns (0.05-0.35), forests (0.01-0.20).

Q3: Why is rainfall measured in meters?
A: Rainfall is typically measured in millimeters, but for volume calculations, we convert to meters (1 mm = 0.001 m) to maintain consistent units with area (m²) and volume (m³).

Q4: Can this calculator be used for different time periods?
A: Yes, but the rainfall value should correspond to the design storm duration you're analyzing (e.g., 24-hour rainfall, 1-hour rainfall).

Q5: What are typical applications of stormwater capacity calculations?
A: These calculations are used in designing drainage systems, sizing retention ponds, planning flood control measures, and meeting regulatory requirements for stormwater management.