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Calcimator

Watershed Area Calculator

Calculate drainage area and morphometric parameters of a watershed from perimeter, shape factor, and longest flow path.

Inputs

km
km

Results

Drainage Area

50 km²

Area (Hectares)

5,000 ha

Area (Acres)12,355.25 acres
Compactness Coefficient1.584
Form Factor0.347
Circularity Ratio0.393
Elongation Ratio0.665
Drainage Density0.24 km/km²
How to Use This Calculator
  1. Enter Watershed Perimeter, Shape Factor, and Longest Flow Path.
  2. Review Drainage Area (km²) and Area (Hectares) (ha).
  3. Use Area (Acres) (acres) and Compactness Coefficient to inform your decision.
  4. Use the chart to visualize the results and explore different scenarios by adjusting inputs.

How the result changes with Watershed Perimeter

Watershed PerimeterDrainage AreaArea (Hectares)
1,00031,250 km²3,125,000 ha
3,500382,812.5 km²38,281,250 ha
6,5001,320,312.5 km²132,031,250 ha
9,0002,531,250 km²253,125,000 ha

What each input means

Watershed Perimeter
Total perimeter length of the watershed boundary in kilometers
Shape Factor
Dimensionless factor (0-1) describing watershed shape; 1 = square, lower = elongated
Longest Flow Path
Length of the longest watercourse from divide to outlet in kilometers

How this is calculated

Formula

A = shapeFactor × (P/4)²; Kc = 0.28 × P / √A

Worked example, using the default values

  1. Identify Input Parameters
    Watershed Perimeter = 40, Shape Factor = 0.5, Longest Flow Path = 12 = 3 input(s) provided
  2. Calculate Drainage Area
    Drainage Area
    50 = 50
  3. Calculate Area
    Area
    5000 = 5000
  4. Calculate Area
    Area
    12355.25 = 12355.25
  5. Calculate Compactness Coefficient
    Compactness Coefficient
    1.584 = 1.584

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