Detention Basin Sizing Calculator
Size a stormwater detention basin: paste an inflow hydrograph (or give a peak flow and storm duration for a triangular one), set the allowable release rate, and get the required storage volume, peak reduction, and time of peak storage from a level-pool storage routing.
Input
Time and flow pairs in the units below. Leave empty to use a triangular hydrograph from the peak flow and base time.
Total duration of the storm hydrograph; the peak occurs at 40% of it.
Constant outflow while the basin holds water, e.g. the pre-development peak.
Extra storage added on top of the routed volume.
Output
| Property | Value |
|---|---|
| No data yet | |
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/detention-basin-sizing-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"hydrograph": "",
"peakInflow": "30",
"baseTime": "120",
"allowableRelease": "8",
"flowUnit": "cfs",
"timeUnit": "min",
"freeboard": "20"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `detention-basin-sizing-calculator` tool (Detention Basin Sizing Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/detention-basin-sizing-calculator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="Detention Basin Sizing Calculator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
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Guides
Estimate how much storage a stormwater detention basin needs. Paste an inflow hydrograph, or give a peak flow and storm duration for a triangular one, set the allowable release rate, and the calculator routes the storm through the basin to find the maximum stored volume, the time it peaks, and how much the peak flow is reduced.
How to use it
- Paste your inflow hydrograph as
time, flowpairs, one per line. Leave it empty to use a triangular hydrograph instead. - For a triangular storm, enter the peak inflow and base time. The peak occurs at 40% of the base time.
- Enter the allowable release rate, often the pre-development peak flow.
- Choose the flow unit (cfs, L/s, m³/s) and time unit (minutes or hours).
- Add a freeboard / safety margin percentage on top of the routed volume.
The method
The tool does a level-pool mass balance, dS/dt = I − O. Outflow is the smaller of the allowable release rate and the water available (inflow plus what is already stored). Whenever inflow exceeds the release rate the surplus is stored, and the basin drains at the release rate afterwards. The required storage is the maximum stored volume.
Limits
This is a planning-level estimate with a constant outflow. It does not model an outlet structure's stage-discharge curve, infiltration, evaporation or tailwater. Final design should follow your local stormwater manual and be checked by a qualified engineer.