Rational Method Runoff Calculator

Estimate peak runoff flow from catchment area, rainfall intensity and runoff coefficient.

How it works

Estimate peak runoff flow from catchment area, rainfall intensity and runoff coefficient.

Formula:
Q = 0.00278 × C × i(mm/h) × A(ha).
Before you use the result: Local rainfall data, drainage criteria, soil behavior and excavation safety requirements can govern the design.

Practical use

Use project-specific rainfall, catchment, soil and excavation information. Drainage and excavation safety can be governed by local regulations and site conditions.

  • Keep units consistent with the source information.
  • Use project-specific densities, pack sizes and coverage rates where provided.
  • Round purchasing quantities to supplier packaging and delivery rules.

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