Time of Concentration Calculator
Estimate how long runoff takes to travel from the hydraulically most distant point to the outlet or design point.
Time of concentration is the travel time through the controlling drainage path.
Time of Concentration Calculator
Estimate travel time using a simple length and velocity method.
This is a screening tool. Local drainage manuals may require specific methods.
What this calculator does
This tool provides a simple travel time estimate using flow path length, average velocity, and optional initial sheet flow time.
Inputs explained
- Flow path length: Length of the runoff travel path.
- Average velocity: Estimated runoff velocity along the selected path segment.
- Initial sheet flow time: Optional starting time for sheet flow before concentrated flow begins.
Limitations
Local drainage manuals may require a specific time of concentration method. This calculator is intended for screening and concept checks.
FAQ
Why does time of concentration matter?
Time of concentration helps select the design rainfall intensity used in peak runoff calculations.
Can this replace local drainage manual methods?
No. Use the method required by the reviewing agency for final drainage design.
Can I use this with the Rational Method?
Yes. Time of concentration is commonly used to select rainfall intensity for Rational Method calculations.
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Need help reviewing this result?
Use this calculator for planning-level checks, then request help if you need a second look at assumptions, units, stormwater criteria, pump sizing, storage volume, or report-ready calculations.