Stormwater Detention Routing Calculator
Route an entered inflow hydrograph through constant-area storage with a square-root level-dependent outlet.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Use endpoint-averaged inflow and backward-Euler outlet discharge; solve a positive quadratic in square root of the next level.
Area(hnext−hprevious)=Δt(mean interval inflow−k√hnext)
Worked example
With no inflow and zero initial depth every level stays zero. Each numerical interval balances stored volume change against input minus output volume.
Assumptions and input details
Constant plan area, no outlet submergence, infiltration, weir/spill or storage limit. End-of-step outlet is a backward-Euler approximation; halve the observation interval with appropriate inflow data to check resolution. Not a drainage facility design or flood prediction.
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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