Detention Storage Calculator
Estimate planning-level detention storage from peak inflow, allowable release rate, and storm duration.
Detention Storage Calculator
Estimate screening-level detention storage based on inflow, allowable release, and duration.
Important limitation
This is a simplified volume estimate based on the difference between inflow and outflow over a selected duration. Real detention design should use local hydrology, routed hydrographs, outlet structure hydraulics, stage-storage, freeboard, emergency overflow, and agency criteria.
Use for early planning only. Do not use as a final detention basin design.
What this calculator does
This tool estimates storage by multiplying the difference between inflow and allowable outflow by a selected duration, then applying a safety factor.
Inputs explained
- Peak inflow: Estimated incoming flow to the basin.
- Allowable outflow: Target release rate or mitigation threshold.
- Critical duration: Time period used for a quick storage estimate.
- Safety factor: Added volume for planning uncertainty.
Limitations
This is not a routed detention basin design. Final design should use hydrology, stage-storage, outlet hydraulics, emergency overflow, freeboard, drawdown, and agency criteria.
FAQ
Does this replace hydrograph routing?
No. It is a simple screening estimate only.
What is allowable outflow?
It is the controlled release rate allowed by the design objective, permit, or local agency.
What if outflow is larger than inflow?
The required storage from this simple method becomes zero, but the site may still require treatment volume or routing checks.
Should I use a safety factor?
For early planning, a safety factor helps account for uncertainty before detailed routing is completed.
Related tools
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.