Hydraulics & drainage · Stormwater & WSUD
On-site detention storage (triangular hydrographs) calculator
Storage from post-development inflow and permissible site discharge using the triangular-hydrograph approximation V = Vin(1 − Qo/Qi).
Standard: Simplified triangular hydrograph method (Boyd / Basha)
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Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Post-development peak inflow | 180 | L/s |
| Inflow hydrograph base time (2 tc) | 30 | min |
| Permissible site discharge | 70 | L/s |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Inflow volume 0.5 Qi tb | 162.0 | m³ |
| Storage Vin(1 − Qo/Qi) | 99.00 | m³ |
- ✓ Outflow < inflow
Method, formulas and assumptions
- Inflow volume 0.5 Qi tb = 0.5*180/1000*30*60 = 162 m³
- Storage Vin(1 − Qo/Qi) = 162*(1-70/180) = 99 m³
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.