Causeway Flow
Commercial
Storm and foul water drainage design and 1D hydraulic modelling software for UK and Irish civil engineers.
4 tools · Topic
Rational Method Tools & Calculators
The Rational Method (Q = CiA) is still the default peak-flow estimate for small urban catchments, and most drainage authorities accept it. Listed here: the FHWA Hydraulic Toolbox, a free desktop program with a rational-method calculator; HydroCAD, a commercial package that runs the method alongside TR-55 and TR-20; and Delta Hydro Studio, which has a browser calculator for it.
Delta Hydro Studio
FreemiumVerified
Browser-based hydrology and hydraulics calculators for practising engineers — no install, report-ready output.
FHWA Hydraulic Toolbox
Gov-Public
A free bundle of FHWA drainage calculators: channels, weirs, curb & gutter, riprap, detention and more.
HydroCAD
Commercial
The US land-development standard for TR-55/TR-20 hydrographs and detention pond design.