Delta Hydro Studio
FreemiumVerified
Browser-based hydrology and hydraulics calculators for practising engineers — no install, report-ready output.
Urban Stormwater & InfrastructureActiveRational MethodCulvert Sizing
6 tools · Topic
Detention & Retention Pond Design Tools
Detention sizing is an iteration loop: inflow hydrograph, stage-storage, outlet rating, route, repeat. The tools below close that loop — pond routing calculators, outlet structure designers and full model workflows for quantity control compliance.
EPA National Stormwater Calculator
Gov-Public
EPA's free tool for estimating site runoff reduction from green infrastructure, with climate scenarios.
Urban Stormwater & InfrastructureStableSuDS & LID DesignStormwater Design
EPA SWMM
Gov-PublicVerified
The public-domain engine of urban drainage: dynamic-wave pipe networks, runoff, LID and water quality.
Urban Stormwater & InfrastructureActiveSWMMSewer Modelling
HydroCAD
Commercial
The US land-development standard for TR-55/TR-20 hydrographs and detention pond design.
Urban Stormwater & InfrastructureActiveDetention DesignTR-55
NetSTORM
Free
CDM Smith's free rainfall statistics and STORM-method screening model — IDF analysis, disaggregation, CSO planning.
Urban Stormwater & InfrastructureActiveIDF CurvesRainfall Data
WinTR-55
Gov-Public
NRCS's official implementation of TR-55 small-watershed hydrology: peaks, hydrographs and storage.
Hydrology & Catchment AnalysisStableTR-55SCS Curve Number