1. What is the Runoff Calculation?

The runoff calculation estimates the volume of stormwater runoff generated from a specific area during a rainfall event. This is essential for designing drainage systems, managing stormwater, and preventing flooding.

2. How Does the Calculator Work?

The calculator uses the runoff formula:

Where:

• \( Rainfall \) — Precipitation amount in millimeters
• \( Area \) — Surface area in square meters

Explanation: The formula converts rainfall depth to volume by multiplying by the area and dividing by 1000 to convert from liters to cubic meters.

3. Importance of Runoff Calculation

Details: Accurate runoff estimation is crucial for urban planning, designing drainage infrastructure, flood risk assessment, and environmental impact studies.

4. Using the Calculator

Tips: Enter rainfall in millimeters and area in square meters. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: Why divide by 1000 in the formula?
A: We divide by 1000 to convert from liters to cubic meters (1 m³ = 1000 liters).

Q2: Does this account for absorption or infiltration?
A: No, this is a simple calculation that assumes all rainfall becomes surface runoff without any absorption.

Q3: What factors affect actual runoff volume?
A: Surface type, slope, soil moisture, vegetation cover, and infiltration capacity all affect actual runoff volumes.

Q4: When is this calculation most accurate?
A: This calculation is most accurate for impervious surfaces like concrete or asphalt where little to no infiltration occurs.

Q5: Can this be used for large watershed areas?
A: For large areas, more complex hydrological models that account for varying land use and soil types are recommended.