HERO E&C has launched H&H Tools, a set of free hydraulics calculators at heroenc.com/hh-tools. They run in a web browser with no account and no fee, next to the HERO E&C Texas screening maps in the Services menu under Engineering Tools.
They are calculation aids. Each one applies a published method to the inputs you enter. The results are not a sealed engineering document, and the engineer of record remains responsible for the design.
The five calculators
Channel Flow — Manning’s equation for open channels and partly full pipes: water depth, flow, slope, bottom width, or pipe diameter; critical depth, Froude number, bed shear, and a rating curve, for a trapezoid, rectangle, triangle, pipe, or surveyed section.
Pipe Flow — partly full gravity flow by Manning’s equation, and full-pipe pressure flow by Hazen-Williams or Darcy-Weisbach with minor losses.
Weir & Orifice — sharp-crested, V-notch, Cipolletti, and broad-crested weirs, the HEC-22 weir equation, orifices, risers, and sluice gates.
Channel Lining — the FHWA HEC-15 shear stress method for grass, riprap, or a lining you describe: permissible shear, stable stone size, and bends.
Manning’s n — n values by source (Chow (1959) via HEC-RAS Table 3-1 for channels, FHWA HDS-5 for culverts and pipes, HEC-22 for gutters) and a Cowan’s method calculator from USGS Water-Supply Paper 2339. “Use this n” carries the value and its source into the other calculators.
How to use them
Pick what you want to find — a water depth, a flow, a slope, or a size — and fill in the numbered steps. The answer appears with a dimensioned section drawing, the flow state in words, and the full results below. Switch between US and SI units at any time.
“Print calculation sheet” produces a sheet with the inputs, equations, results, warnings, references, and the source of every Manning’s n. The page address carries every input, so a colleague can open the same calculation from a shared link, and a project file or CSV keeps the numbers for later. Calculations run in your browser; HERO E&C does not receive or store your inputs or results.
Tested against reference cases
Every calculator has a Verification tab listing the cases it is tested against — worked examples from FHWA, TxDOT, and USGS publications and runs of FHWA’s public-domain Hydraulic Toolbox — with the number of values compared and the largest difference for each case. The table comes from the same tests that run whenever the code changes, so the page shows only results the tests produced. Limits and known gaps are listed on each page.
Who they are for
Drainage, floodplain, and roadway engineers, plan reviewers at cities and counties, and students who need a quick single-element calculation they can check — a channel capacity, a weir rating, a lining check — without opening a desktop program, and a printable record of how the number was found.
What comes next
A culvert calculator using the FHWA HDS-5 method is in testing. Hydrology calculators built on the NOAA Atlas 14 rainfall behind the Texas Atlas 14 Rainfall Map are planned after that.
Try them on your next project
HERO E&C is a San Antonio civil and water resources engineering firm founded in 2025 and led by Seoyoung Kim, Ph.D., P.E., CFM. When a project needs a drainage study, channel or culvert design, or HEC-HMS and HEC-RAS models, HERO E&C can help.