1. What is Surface Runoff Calculation?

Surface Runoff refers to water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle. This calculator helps determine the surface runoff depth based on hydrograph analysis.

2. How Does the Calculator Work?

The calculator uses the surface runoff formula:

Where:

• \( Sr \) — Surface Runoff (m³/s)
• \( \Sigma O \) — Sum of Ordinates (m³/s)
• \( \Delta t \) — Time Interval (seconds)
• \( A_{HA} \) — Catchment Area for Hydrograph Analysis (m²)

Explanation: The formula calculates surface runoff by multiplying the sum of ordinates by the time interval, dividing by the catchment area, and applying a conversion factor of 0.36.

3. Importance of Surface Runoff Analysis

Details: Accurate surface runoff calculation is crucial for water resource management, flood prediction, urban planning, and environmental impact assessments.

4. Using the Calculator

Tips: Enter sum of ordinates in m³/s, time interval in seconds, and catchment area in m². All values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What are ordinates in hydrograph analysis?
A: Ordinates refer to the values of direct runoff at different time intervals in a hydrograph.

Q2: Why is the 0.36 factor used in the formula?
A: The 0.36 factor is a conversion constant that accounts for unit conversions and empirical relationships in runoff calculations.

Q3: What is a typical range for surface runoff values?
A: Surface runoff values vary widely depending on rainfall intensity, soil type, land use, and catchment characteristics.

Q4: How does catchment area affect surface runoff?
A: Larger catchment areas generally result in higher total runoff volumes but lower runoff intensity per unit area.

Q5: Can this calculator be used for urban areas?
A: Yes, but urban areas with impervious surfaces may require additional considerations for accurate runoff estimation.