How to use the peak runoff calculator
Estimate peak stormwater runoff from a catchment using the rational method. Enter runoff coefficient, rainfall intensity, catchment area in the fields above; the peak runoff flow are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “rational method runoff”, “peak flow stormwater”, “catchment runoff calculation”, “calculate peak runoff”, “find peak runoff flow”.
Formula
Variables
- C — Runoff coefficient
- i — Rainfall intensity (mm/h)
- A — Catchment area (ha)
Worked example
With runoff coefficient = 0.6, rainfall intensity = 50 mm/h, catchment area = 10 ha, the calculator gives peak runoff flow ≈ 0.8333333 m³/s; peak runoff flow ≈ 833.3333 L/s.
Frequently asked questions
What is the peak runoff calculator used for?
Estimate peak stormwater runoff from a catchment using the rational method. It helps with questions such as “rational method runoff”, “peak flow stormwater”, “catchment runoff calculation”.
What is the formula for the peak runoff calculation?
Peak runoff flow (m³/s) = C × i × A / 360. Peak runoff flow (L/s) = [Peak runoff flow] × 1000. Here C is runoff coefficient, i is rainfall intensity (mm/h), A is catchment area (ha).
What inputs do I need for the peak runoff (rational method) calculator?
You need runoff coefficient, rainfall intensity in mm/h, catchment area in ha. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the peak runoff calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the peak runoff result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.