Rational Method Peak Flow Calculator

Calculate peak discharge Q = C·i·A/360 (metric). Intensity i from IDF curve at time of concentration T_c. Valid for small watersheds < 80-200 ha (200-500 acres). Urban and rural applications.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)
σy — Normal Stress Y (MPa)
τxy — Shear Stress (MPa)
⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.
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How It Works

Calculate peak discharge Q = C·i·A/360 (metric). Intensity i from IDF curve at time of concentration T_c. Valid for small watersheds < 80-200 ha (200-500 acres). Urban and rural applications

Each component has a specific meaning:

  • IDF curve at time of concentration T_c — The idf curve at time of concentration t_c recorded for the patient or scenario being assessed.

Note: Interpret the rational method result against the clinical thresholds and context described above.

How to Use

Enter the IDF curve at time of concentration T_c for the patient or scenario you are assessing. Calculate peak discharge Q = C·i·A/360 (metric). Intensity i from IDF curve at time of concentration T_c. Valid for small watersheds < 80-200 ha (200-500 acres). Urban and rural applications. Use the rational method result to inform your clinical assessment.

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Frequently Asked Questions