HydraLink Integration

HydraStorm's companion application HydraLink provides stormwater hydrology modeling including rainfall-runoff analysis, detention pond design, and culvert analysis. Import HydraLink results directly into HydraStorm to drive your storm drain hydraulic design.

Supported File Types

Extension	Description	Contents
.hyd	HydraLink native project file	Basins, junctions, ponds, storm events, full model definition
.hlresults	Pre-computed results export	Peak flows, outflows, volumes, stages

Setup

1. Set the hydrology mode to HydraLink in Project Settings > Hydrology.
2. Browse to the .hyd or .hlresults file using the file picker.
3. Select a Plan if the .hyd file contains multiple plans.
4. Select the Primary Storm (design storm) and optionally a Secondary Storm (check storm).
5. Click Import to match basins to structures and compute flows.

Flow Matching Pipeline

HydraStorm uses a multi-step pipeline to match HydraLink elements (basins, junctions, ponds) to Civil 3D pipe network structures. The matcher tries each strategy in order and stops at the first successful match:

1. Exact name match — the HydraLink element name matches the structure name exactly.
2. Normalized name match — both names are normalized by stripping common prefixes (e.g., "Basin-", "Jct-") before comparison.
3. Substring match — one name is contained within the other.
4. Levenshtein distance — fuzzy matching with a minimum 60% similarity threshold.
5. Spatial proximity — coordinate-based matching within a configurable radius (default 5 ft).
6. Manual assignment — unmatched elements can be assigned manually via the Hydrology Table.

Basin vs Junction Intelligence

HydraLink models often include both basins (drainage areas) and junctions (confluence points that accumulate basin flows). HydraStorm handles this intelligently:

• If a HydraLink junction is located near a pipe network inlet, its accumulated parameters are used (total area, weighted C, composite Tc from all contributing basins).
• Contributing basins upstream of that junction are marked as consumed to prevent double-counting.
• This lets you match at the junction level without worrying about also matching the individual basins.

Flow Sources

Different HydraLink element types provide flow data from different result fields:

Element Type	Flow Field	Description
Basin	peak_flow_cfs	Peak runoff from the drainage area
Pond	peak_outflow_cfs	Routed outflow after detention
Culvert	peak_outflow_cfs	Outflow from the culvert analysis

File Watcher

HydraStorm monitors the linked HydraLink file for external changes. When HydraLink saves an update to the file, HydraStorm displays a notification in the status bar prompting you to reload the updated data.

This enables a live workflow: make changes in HydraLink, save, then reload in HydraStorm without manually re-importing.

Rational Method from HydraLink

In rational-method modes (HydraLink, Parcels, Manual), HydraLink can provide basin parameters — drainage area, runoff coefficient C, and time of concentration Tc — rather than just peak flows. This allows HydraStorm to perform its own Tc accumulation through the pipe network and interpolate rainfall intensity from local IDF data.

This is particularly useful when the pipe network layout differs from the HydraLink junction network, since HydraStorm will recompute travel times based on actual pipe lengths and velocities.