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Configuration principals

The Configuration Setup will enable calculations of Peak Runoffs from Watersheds according to the Rational Method:

Q = C * i * A

Q: Peak Runoff discharge from a Watershed measured in liters/second
C: Runoff Coefficients from the Watershed (see detailed explanation below)
i: Rainfall Intensity for a given Duration and Frequency measured in mm/hour
A: Watershed Area measured in hectare (ha) where 1ha = 10.000m2

The Runoff Coefficient

The Runoff Coefficient (C) is a dimensionless number between 0 and 1 that represents the portion of rainfall that becomes surface runoff - or in short - it tells you how absorbent a surface is.

What the number means

• A value of 0.90: Means 90% of the rain runs off the surface

• A value of 0.10: Means only 10% of the rain runs off, while 90% soaks into the ground or is trapped

Factors that influence C

• Surface Type: Impermeable surfaces (roads, roofs) have high coefficients; permeable surfaces (gardens, forests) have low coefficients.

• Slope: Steeper terrain gives water less time to soak in, increasing the coefficient.

• Soil Type: Clay soils (which don't absorb water well) have higher coefficients than sandy soils.

• Saturation: If the ground is already soaked from a previous storm, the coefficient increases because the "sponge" is full.