Civil 3D Integration

Overview

HydraLink ships a companion add-in for Autodesk Civil 3D that lets you run drainage calculations directly on Civil 3D parcels and hand the completed model to HydraLink desktop with a single save. Your parcel data stays in the drawing throughout design; when you’re ready to solve, HydraLink desktop builds a project from it, and once you solve, the results flow back into the drawing automatically.

Setup

Run the HLSETUP command once per drawing to add HydraLink parcel properties to your Civil 3D parcels. If you skip this step, the properties are added automatically the first time you use the calculator. These properties hold the hydrologic parameters the calculator needs on each parcel: runoff coefficient (C), curve number, time of concentration, land use, soil group, and basin assignment (drains-to).

The Calculator Palette (HLCALC)

HLCALC opens a dockable palette with three tabs for building and reviewing your drainage model without leaving Civil 3D.

Basins Tab

One row per basin, showing area, C, Tc, Drains To, and computed peak flow (Q) for each return period, updated live as you edit parcels. Selecting a row highlights the corresponding parcel in the drawing. A bulk-apply bar lets you edit a parameter across many selected basins at once.

• The Weighted C worksheet builds an area-weighted composite runoff coefficient from a land-use breakdown, using reusable C tables.
• The Tc worksheet is a TR-55 style sheet flow / shallow concentrated flow / channel segment builder that can link to a feature line profile for channel segments.

Junctions Tab

Define what drains where, from basins to junctions and from junctions to downstream junctions, and place junction markers directly in the drawing. Each junction shows total accumulated flow per return period. Network overlays and a zoom-to-network command help you keep track of the drainage layout as it grows.

Storms Tab

Pick your design return periods, then supply rainfall data by fetching NOAA Atlas 14 precipitation for a location (or by picking a point on the drawing), importing a CSV, or entering values manually. An IDF curve chart and b/d/e coefficient entry are available (TxDOT convention i = b/(Tc+d)^e), and you choose which intensity method the calculator should use.

One-Step Handoff to Desktop

When your basin and junction network is ready, click Save .hyd on the palette. This writes a complete HydraLink project file: one plan per Civil 3D site, with basins and junctions positioned geographically and parcel boundaries shown on the desktop map. Open the file in HydraLink desktop and run the solver as usual.

Results Back to CAD

After solving and saving in the desktop app, the results are picked up back in the drawing:

• HLIMPORT writes the computed flows and intensities to the parcel properties.
• HLTABLE places a junction summary table (local and total Q) in the drawing.

The palette watches for updated results while it’s open and prompts you when a new solve is available to import.

Staying in Sync

If the drawing changes after handoff, whether areas are adjusted, parameters edited, or new parcels added, the desktop app shows a sync preview of exactly what changed and lets you accept or skip each change individually. It never silently overwrites your design data. Advisory drift warnings also let you know if drawing values have diverged from the last computed results, so nothing is out of sync without your knowledge.

Command Reference

Command	Description
HLSETUP	Adds HydraLink parcel properties to the current drawing.
HLCALC	Opens the dockable calculator palette (Basins, Junctions, Storms).
HLIMPORT	Writes computed results from a solved HydraLink project back to parcel properties.
HLTABLE	Places a junction summary table (local + total Q) in the drawing.
HLEXPORT	Exports parcel data manually; normally not needed, since Save .hyd handles this.