Calculadora de Escoamento de Bacia — Formula

How to Calculate Watershed Runoff

The rational method estimates stormwater runoff based on rainfall, area, and land cover.

Formula

Runoff = Area * Rainfall * Runoff Coefficient

Typical Runoff Coefficients (C)

  • Forest: 0.10-0.20
  • Grass/park: 0.20-0.35
  • Suburban: 0.40-0.60
  • Urban/commercial: 0.70-0.95
  • Parking lot: 0.85-0.95

    • Exemplo Resolvido

    A 50-acre suburban watershed with 2 inches of rainfall and runoff coefficient of 0.5.

    1. Runoff acre-inches: 50 * 2 * 0.5 = 50 acre-inches
    2. Runoff gallons: 50 * 27,154 = 1,357,700 gallons
    3. Runoff acre-feet: 1,357,700 / 325,851 = 4.17 acre-feet
    4. Retained: 50 * 2 * 0.5 * 27,154 = 1,357,700 gallons