Rational Method Runoff Basics

Wanneer dit van toepassing is

Use this guide for early drainage conversations when you must show assumptions for intensity, area, and coefficient transparently.

Te gebruiken tool

Browser-based preliminary check for Rational Method Runoff Calculator — fast estimates, not code or stamped design output.

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Stappen

  1. 1Define catchment boundary and contributing impervious vs pervious fractions.
  2. 2Pick a design storm intensity and duration appropriate to local guidance.
  3. 3Choose a runoff coefficient consistent with cover type and slope.
  4. 4Compute peak flow and sanity-check magnitude with experience and alternate methods.
  5. 5Move to hydrograph routing when storage and timing effects dominate.

Voorbeelden

  • Parking lot inlet sizing discussion.
  • Roof drain peak for a small building.

Vermijd dit

  • Using rational method for very large basins without checking validity limits.
  • Mixing intensities from different return periods without labeling.
  • Ignoring downstream constraints while only sizing a pipe segment.

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Veelgestelde vragen

Is this code-compliant?

It is a teaching-oriented screening tool; local codes may require approved hydrology methods.

Snowmelt?

Not included; extend model when winter hydrology matters.

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