AquaSWMM

Migration guide

Taking a Civil 3D pipe network into AquaSWMM

If you lay out storm drainage as a Civil 3D pipe network, you can analyse it in AquaSWMM without redrawing it. Export the network as LandXML, open that file in AquaSWMM, and you have both a Rational-method storm-sewer design and an EPA SWMM 5 model of the same pipes. When the design is done, AquaSWMM writes the network back out as LandXML for Civil 3D.

AquaSWMM is a standalone desktop app for Windows, macOS and Linux. It costs $490 a seat per year, or $1,200 for five seats.

1. Export the network from Civil 3D

Export the pipe network to a LandXML 1.2 file using Civil 3D’s LandXML export. AquaSWMM reads the LandXML that Civil 3D actually writes:

  • Per-pipe invert records.
  • Sump and rim elevations on structures.
  • Catchment data attached to pipes: area, runoff coefficient and inlet time.
  • The “null structure” at the end of a run, read as the outfall from the direction of flow.

If your network uses Hydraflow Storm Sewers instead, open its .stm file directly; that route carries more (see the Hydraflow guide).

2. Open the LandXML in AquaSWMM

Use File > Import > LandXML Pipe Network (.xml)… or File > Open, or drop the file on the window (manual §13.1). The source file is never overwritten: the converted model has no path until you save it as a .inp.

LandXML describes geometry, not hydraulics, so check three things after the import:

  • Manning’s n. LandXML carries a pipe material, not an n value, so AquaSWMM assigns one from the material: 0.013 for concrete and anything unrecognised, 0.012 for HDPE, PVC, ductile iron and steel, and 0.024 for corrugated metal. Change any that don’t match your design standard; the attribute table sets a whole column at once (manual chapter 6).
  • The design storm. LandXML has no IDF curve. Enter your IDF coefficients, return period and minimum Tc in the design panel. Or use File > Import > NOAA Atlas 14 IDF (.csv)…, which fits the curves from a NOAA precipitation-frequency table for you (manual §12.1).
  • Structure types. Civil 3D doesn’t label a structure as an inlet, junction or outfall, so AquaSWMM infers the type from its geometry, part description, name and the direction of flow in its pipes. Look over the outfalls and terminal inlets.

3. Design it: Analyze

Analyze (F6) runs AquaSWMM’s storm-sewer engine on the network: Rational method, Manning, standard-step HGL, HEC-22 inlets and access-hole losses, catalog sizing and a design review. Auto-size previews recommended sizes before writing them into the model as one undo step. The design report comes out as PDF or HTML (manual chapter 12). The equations are in chapter 15.

4. Check it in EPA SWMM 5

The same import writes a standard SWMM model. Each drainage area becomes a subcatchment, and the gage gets a 2-hour design storm built from your IDF curve by the alternating-block method (manual §13.1). Run it in dynamic wave to see timing, storage and backwater that a Rational-method run can’t show. AquaSWMM runs EPA’s runswmm.exe unmodified and records the engine version and the SHA-256 of the executable with every run. The .inp stays EPA’s format, so it also opens in the free EPA SWMM program.

The subcatchments’ impervious fraction, width and slope are derived from C and area, not measured. The importer lists its assumptions (manual §15.7). Review them before you rely on the SWMM run.

5. Send the design back to Civil 3D

Design Reports > Export Design Network (LandXML)… writes the analysed network as a LandXML pipe network, which Civil 3D imports as a pipe network (manual chapter 12). The model, its storm and the design report stay in AquaSWMM for the drainage report.

Help while you work, at any hour

AquaSWMM includes an AI support assistant that has read the whole manual. Ask it why a structure was read as an outfall, what a design-review finding means, or where a setting lives. It answers in seconds and names the section to check. It is on every plan and the free trial.

Try it on your own network

The 30-day trial is the full app. If your LandXML doesn’t come across cleanly, email support@aquaswmm.com. I’ll send a 90-day evaluation key and look at the file with you.

Autodesk, Civil 3D and Hydraflow are trademarks of Autodesk, Inc. AquaSWMM is independent software from HydroComplete LLC and is not affiliated with or endorsed by Autodesk or the U.S. EPA. LandXML is an open data standard. Behaviour described is AquaSWMM 0.12.7.