Average Rainfall Intensity Given Runoff Rate Of Rainwater From Bridge During Rainstorm Calculator

Formula Used:

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

Intensity of Rainfall (I):

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1. What is the Rainfall Intensity Formula?

The formula calculates rainfall intensity based on peak runoff rate, runoff coefficient, and catchment area. It's particularly useful for bridge drainage design during rainstorms to ensure proper water management.

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

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

Explanation: The formula calculates rainfall intensity by dividing the peak runoff rate by the product of the runoff coefficient and catchment area, with a constant adjustment factor of 1.00083.

3. Importance of Rainfall Intensity Calculation

Details: Accurate rainfall intensity calculation is crucial for bridge drainage design, flood prediction, and stormwater management systems to prevent water accumulation and structural damage.

4. Using the Calculator

Tips: Enter peak runoff rate in m³/s, runoff coefficient (between 0-1), 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. Paved surfaces have higher coefficients (0.8-0.95) while vegetated areas have lower coefficients (0.3-0.5).

Q2: Why is the constant 1.00083 used in the formula?
A: This constant provides a conversion factor to ensure proper units and account for specific hydrological conditions in bridge drainage calculations.

Q3: How is peak runoff rate determined?
A: Peak runoff rate is typically calculated using hydrological models that consider rainfall patterns, catchment characteristics, and drainage system capacity.

Q4: What factors affect runoff coefficient?
A: Surface type, slope, soil composition, vegetation cover, and antecedent moisture conditions all influence the runoff coefficient value.

Q5: How accurate is this calculation for bridge design?
A: This provides a good estimate for preliminary design, but final bridge drainage systems should consider local rainfall data, safety factors, and engineering standards.