Flowpath Engineering Portal
Stormwater Detention Tank Routing — NZ Design Calculator
Design and verify stormwater detention tanks with full hydrograph routing. Calculate storage volumes, outlet sizing, and peak flow attenuation for Auckland Council and NZ-wide compliance.
What this tool does
Hydrograph Routing
Route stormwater inflow hydrographs through detention storage using the Modified Puls method to verify peak flow attenuation meets council requirements.
TP108 Methodology
Generate design storms and catchment runoff calculations based on Auckland Council's TP108 technical publication for stormwater management.
Outlet & Orifice Sizing
Size tank outlets, orifice plates, and overflow weirs to achieve the required post-development discharge rate for your site.
Storage Volume Optimisation
Iteratively size detention tanks to find the minimum volume that satisfies pre-development peak flow matching across multiple storm durations and return periods.
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Open Detention Routing CalculatorPart of the Flowpath Engineering suite of free civil engineering tools for New Zealand.