Runoff Coefficient Given Runoff Rate Of Rainwater From Bridge During Rainstorm Calculator

Runoff Coefficient Formula:

\[ C_r = \frac{q_p}{1.00083 \times I \times A_{catchment}} \]

Runoff Coefficient (Cᵣ):

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1. What is the Runoff Coefficient?

The Runoff Coefficient is a dimensionless coefficient that relates the amount of runoff to the amount of precipitation received. It represents the fraction of rainfall that becomes surface runoff rather than being absorbed or evaporated.

2. How Does the Calculator Work?

The calculator uses the Runoff Coefficient formula:

\[ C_r = \frac{q_p}{1.00083 \times I \times A_{catchment}} \]

Where:

\( C_r \) — Runoff Coefficient (dimensionless)
\( q_p \) — Peak Rate of Runoff (m³/s)
\( I \) — Intensity of Rainfall (m/s)
\( A_{catchment} \) — Catchment Area for Rainstorm (m²)
1.00083 — Conversion factor

Explanation: The equation calculates the proportion of rainfall that becomes surface runoff based on peak runoff rate, rainfall intensity, and catchment area.

3. Importance of Runoff Coefficient Calculation

Details: Accurate runoff coefficient calculation is crucial for hydrological modeling, stormwater management, flood prediction, and urban drainage system design. It helps engineers design appropriate drainage infrastructure to handle stormwater runoff.

4. Using the Calculator

Tips: Enter peak rate of runoff in m³/s, rainfall intensity in m/s, and catchment area in m². All values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What factors affect the runoff coefficient?
A: Surface type, slope, soil type, vegetation cover, and antecedent moisture conditions all influence the runoff coefficient value.

Q2: What are typical runoff coefficient values?
A: Values range from 0.05-0.10 for forested areas, 0.10-0.25 for grassy areas, 0.30-0.50 for agricultural land, and 0.70-0.95 for paved urban areas.

Q3: Why is the conversion factor 1.00083 used?
A: The conversion factor accounts for unit consistency and ensures dimensional homogeneity in the equation.

Q4: How does rainfall intensity affect runoff coefficient?
A: Higher rainfall intensity typically results in higher runoff coefficients as the ground becomes saturated more quickly, reducing infiltration capacity.

Q5: Can this calculator be used for both urban and rural areas?
A: Yes, the formula applies to both urban and rural catchments, though the resulting coefficient values will differ based on surface characteristics.