1. What is the Peak Runoff Rate Formula?

The formula calculates the peak rate of runoff from a bridge catchment area during a rainstorm. It considers the runoff coefficient, rainfall intensity, and catchment area to estimate the maximum discharge rate.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( q_p \) — Peak rate of runoff (m³/s)
• \( C_r \) — Runoff coefficient (dimensionless)
• \( I \) — Intensity of rainfall (m/s)
• \( A_{\text{catchment}} \) — Catchment area for rainstorm (m²)

Explanation: The formula accounts for the relationship between rainfall intensity, catchment characteristics, and the resulting peak runoff rate.

3. Importance of Runoff Rate Calculation

Details: Accurate runoff rate estimation is crucial for bridge design, drainage system planning, flood risk assessment, and infrastructure protection during rainstorms.

4. Using the Calculator

Tips: Enter runoff coefficient (0-1), rainfall intensity in m/s, and catchment area in m². All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical runoff coefficient value?
A: Runoff coefficients typically range from 0.3-0.95, depending on surface type, slope, and soil conditions.

Q2: How is rainfall intensity measured?
A: Rainfall intensity is usually measured in mm/hour but can be converted to m/s for calculations (1 mm/h = 2.77778×10⁻⁷ m/s).

Q3: What factors affect the runoff coefficient?
A: Surface permeability, slope, vegetation cover, and soil type all influence the runoff coefficient value.

Q4: Why is the constant 1.00083 used?
A: This constant accounts for unit conversions and empirical adjustments in the formula derivation.

Q5: When is this calculation most important?
A: This calculation is critical during bridge design, stormwater management planning, and flood risk assessment for infrastructure projects.