🌩️ StormNET · Quick Tutorial 1 of 3

StormNET Synthetic Model

Step-by-step walkthrough of building a basic stormwater network: subcatchments, conduits, junctions, outfalls, rain gages, and running a simulation.

StormNET Tutorial 1 Prereq: MAGNET4WATER account 7 sections · detailed step navigation

1Getting Started

Step 1 — Launch the Platform

Browse to https://www.magnet4water.org/stormnet/

This site hosts the complete, integrated platform for storm water network modeling, analysis, and visualization. The default interface includes: menu bar (top), network objects and options (left panel), map display (working environment), and object edit tools (toolbar).

Figure 1 — StormNET interface: menu bar, network objects panel, map display, and toolbar
Figure 1 — StormNET interface: menu bar, network objects panel, map display, and toolbar

Step 2 — Create an Account or Log In

To create an account or log in, click Credentials in the menu bar.

  • New users: Click My Account to create a new account. Complete the registration form. The email you provide is used for resetting your password.
  • Existing users: Click Login to sign in with your existing credentials.

Once logged in, use Credentials → My Account to change your password, update your email or user type, or view and download previously executed models.

Figure 2 — StormNET login: click Credentials in the menu bar, then My Account (new users) or Login (existing users)
Figure 2 — StormNET login: click Credentials in the menu bar, then My Account (new users) or Login (existing users)

2Add & Edit Subcatchments

💡 What Makes a Subcatchment?

Every subcatchment is defined by four key properties: Area (how much land collects rain), Imperviousness (the fraction that's paved — the single biggest driver of urban flooding), Slope (how fast water moves), and Width (which controls sheet-flow travel time). At 50% imperviousness, half the subcatchment generates rapid, unfiltered runoff while the other half absorbs and slows it. Changing this one parameter from 20% to 80% can double peak flows — which is exactly what urbanization does to watersheds.

Step 3 — Draw Subcatchments

Navigate to Hydrology → Subcatchments → Start Drawing.

The cursor turns into a blue circle, indicating Drawing Mode is active. Use single-clicks to add corner vertices of the subcatchment polygon. A double-click closes the subcatchment. Repeat to draw the 2nd and 3rd subcatchments.

Figure 3 — Hydrology → Subcatchments → Start Drawing: click vertices, double-click to close
Figure 3 — Hydrology → Subcatchments → Start Drawing: click vertices, double-click to close
Figure 4 — Three subcatchments drawn on the map
Figure 4 — Three subcatchments drawn on the map

Step 4 — Edit Subcatchment Properties

Navigate to Hydrology → Subcatchments → Edit Subcatchments. Select each subcatchment by its ID and set: Area = 4, Width = 400, % Impervious = 50, Subarea Routing = OUTLET, Percent Routed = 100.

Figure 5 — Subcatchment Editor: select subcatchment by ID
Figure 5 — Subcatchment Editor: select subcatchment by ID
Figure 6 — Set Area, Width, % Impervious, Subarea Routing, and Percent Routed
Figure 6 — Set Area, Width, % Impervious, Subarea Routing, and Percent Routed

Step 5 — Set Infiltration Parameters

In the Subcatchment Editor, navigate to Infiltration/Pollutants/Land Uses tab. Select MODIFIED_GREEN_AMPT as the Infiltration Method. Set Suction Head = 3.5, Conductivity = 0.5, Initial Deficit = 0.26. Click Save.

Figure 7 — Modified Green-Ampt infiltration parameters: suction head, conductivity, initial deficit
Figure 7 — Modified Green-Ampt infiltration parameters: suction head, conductivity, initial deficit
Why Modified Green-Ampt? This method models infiltration as a wetting front advancing into soil — physically intuitive for event-based simulations. Sandy soils have high conductivity (fast infiltration, less runoff); clay soils have low conductivity (more runoff). These parameters directly control how much rainfall becomes surface flow vs. groundwater recharge.

3Build the Hydraulic Network

💡 How the Network Carries Water

Subcatchments generate runoff. The hydraulic network carries it. Junctions are connection points — manholes where pipes meet. Conduits are the pipes, sized by diameter and slope. The outfall is where water exits the system. Drawing direction matters: always draw conduits in the direction of flow — the start node is upstream, the end node is downstream. This defines the flow direction in the model. While it's good practice to design pipes going downhill (and reverse slopes should be avoided), a reverse slope isn't "illegal" — but drawing a pipe against the flow direction will produce wrong results. In this tutorial, junctions descend from 120 ft to 100 ft, so flow direction and slope direction align naturally.

Step 6 — Add Junctions

Navigate to Hydraulics → Nodes → Junctions → Start Drawing. Click to add four junctions. Then edit each via Edit Junctions with the invert elevations shown below. Set Max Depth = 4 for all.

JunctionInvert El (ft)
J496
J590
J693
J788
Figure 8 — Hydraulics → Nodes → Junctions → Start Drawing
Figure 8 — Hydraulics → Nodes → Junctions → Start Drawing
Figure 9 — Junction Data Editor: set invert elevations and max depth for each junction
Figure 9 — Junction Data Editor: set invert elevations and max depth for each junction

Step 7 — Add Conduits

Navigate to Hydraulics → Links → Conduits → Start Drawing. Click once on the upstream junction to snap the start; double-click the downstream junction to snap the end. Draw: J4→J5, J5→J7, and J6→J7.

Important: Always draw conduits in the direction of flow — start node is upstream, end node is downstream. The drawing direction defines the flow direction. A reverse slope is possible but drawing against the flow direction will give wrong results. Every link must have both a starting and ending node.
Troubleshooting tip: If you see unexpected flooding at a junction — and adjusting pipe slopes, diameters, or invert elevations doesn't fix it — the most likely cause is a conduit drawn against the flow direction. The model interprets the drawing direction as the flow path, so a backwards conduit acts like a dead end, trapping water at the junction. Delete the conduit and redraw it in the correct direction (upstream → downstream). This is one of the most common and hardest-to-diagnose modeling errors.
Figure 10 — Drawing a conduit: click upstream junction, double-click downstream junction
Figure 10 — Drawing a conduit: click upstream junction, double-click downstream junction
Figure 11 — Three conduits connecting junctions in the network
Figure 11 — Three conduits connecting junctions in the network

Step 8 — Add Outfall

Navigate to Hydraulics → Nodes → Outfalls → Start Drawing. Click to place the outfall. Edit via Edit Outfalls and set Invert Elevation = 85 ft.

Figure 12 — Adding an outfall to the map
Figure 12 — Adding an outfall to the map
Figure 13 — Outfall editor: set invert elevation to 85 ft
Figure 13 — Outfall editor: set invert elevation to 85 ft

Step 9 — Connect Outfall & Edit Conduits

Add a fourth conduit: J7 → Outfall. Then edit all conduits: Length = 400, Shape = Circular, Max Depth = 1.0 for C1–C3, Max Depth = 1.5 for C4.

Figure 14 — Fourth conduit connecting Junction 7 to the Outfall
Figure 14 — Fourth conduit connecting Junction 7 to the Outfall
Figure 15 — Edit conduit properties: length, max depth, and shape for each conduit
Figure 15 — Edit conduit properties: length, max depth, and shape for each conduit

4Assign Outlets & Rain Gage

💡 Connecting Land to Pipes

A subcatchment doesn't "know" where to send its runoff until you assign an outlet node. A rain gage doesn't affect a subcatchment until you link them. These connections are the logic layer: rainfall drives a subcatchment, the subcatchment drains to a junction, the junction feeds a conduit. If any link is missing, that part of the system is disconnected. StormNET makes these relationships explicit — you can see exactly which rain drives which catchment and which junction receives its runoff.

Step 10 — Assign Subcatchment Outlets

Edit each subcatchment and set Outlet Node Type = Junction: Subcatchment 1 → J4, Subcatchment 2 → J5, Subcatchment 3 → J6. Save after each.

Figure 16 — Assign Junction 4 as the outlet for Subcatchment 1
Figure 16 — Assign Junction 4 as the outlet for Subcatchment 1
Figure 17 — Repeat outlet assignment for Subcatchments 2 and 3
Figure 17 — Repeat outlet assignment for Subcatchments 2 and 3

Step 11 — Add & Edit Rain Gage

Navigate to Hydrology → Rain Gages → Start Drawing. Place the rain gage, then edit: Time Interval = 1:00, Series Name = 2hr, Rain Format = INTENSITY, Rain Unit = IN.

Figure 18 — Adding a rain gage to the map
Figure 18 — Adding a rain gage to the map
Figure 19 — Rain gage editor: time interval, series name, rain format, and units
Figure 19 — Rain gage editor: time interval, series name, rain format, and units

Step 12 — Edit the Time Series

Navigate to Time Series → Edit Time Series. Select the 2Hr series. Delete existing entries, add 7 new rows with Date = 1/1/2002 and the rainfall data below. Click Save Record.

Time (H:M)Intensity (in/hr)
0:000
1:000.5
2:001.0
3:000.75
4:000.5
5:000.25
6:000
Figure 20 — Time Series editor: select Edit mode and choose the 2Hr series
Figure 20 — Time Series editor: select Edit mode and choose the 2Hr series
Figure 21 — Enter the 7-row rainfall time series with date and intensity values
Figure 21 — Enter the 7-row rainfall time series with date and intensity values

5Configure & Run Simulation

💡 Kinematic Wave vs. Dynamic Wave

Kinematic Wave routing assumes gravity and friction drive flow, with no backwater effects — simpler, faster, good for dendritic networks. Dynamic Wave solves the full Saint-Venant equations — handling backwater, surcharging, reverse flow, and pressurized conditions. This tutorial uses Kinematic Wave because the network is simple and gravity-driven. For complex urban systems with flat grades, combined sewers, or storage interactions, Dynamic Wave is essential — and StormNET supports both.

Step 13 — Set Simulation Options

Navigate to Options → Edit Options. Enable Rainfall/Runoff and Flow Routing. Set Routing Model = Kinematic Wave, Infiltration Model = Modified Green Ampt. Save.

Figure 22 — Simulation options: enable process models, set routing and infiltration methods
Figure 22 — Simulation options: enable process models, set routing and infiltration methods

Step 14 — Set Dates

In the Dates tab: Start Analysis = 1/1/2002 12:00 AM, Start Reporting = 1/1/2002 12:00 AM, End Analysis = 1/1/2002 12:00 PM (12-hour simulation).

Figure 23 — Dates tab: start and end times for 12-hour simulation
Figure 23 — Dates tab: start and end times for 12-hour simulation

Step 15 — Set Time Steps

In the Time Steps tab: Reporting Step = 0:05:00, Dry Weather Runoff = 1:00:00, Wet Weather Runoff = 0:15:00.

Figure 24 — Time step settings: reporting, dry weather, and wet weather intervals
Figure 24 — Time step settings: reporting, dry weather, and wet weather intervals

Step 16 — Save & Run

Save: File → Save Model. Run: Project → Run Simulation. The Status Window shows errors (if any) and mass balance results.

Figure 25 — Save model and run simulation
Figure 25 — Save model and run simulation
Figure 26 — Simulation status window: error check and mass balance
Figure 26 — Simulation status window: error check and mass balance

6Visualize Results

💡 Three Views, Three Questions

The Network Map answers "where?" — color-coded nodes and links reveal spatial patterns. The Profile View answers "how?" — a cross-section shows water levels relative to pipe crowns and inverts. The Time Series answers "when?" — flow hydrographs show peak timing and magnitude. The map finds the problem, the profile diagnoses it, the time series quantifies it. A skilled modeler uses all three.

Step 17 — Network Map Results

Navigate to View → Map Browser. Select Subcatchment = Runoff, Node = Head, Link = Velocity, Date = 01/01/2002, Time = 6:20:00. Map objects are color-coded by parameter values.

Figure 27 — Color-coded network map: runoff, head, and velocity at t = 6:20
Figure 27 — Color-coded network map: runoff, head, and velocity at t = 6:20

Step 18 — Profile Visualization

Navigate to Report → Graph → Profile. Double-click J4 and click + next to Start Node. Double-click J8 (outfall) and click + next to End Node. Click Flow Path, then 3D Profile.

Figure 28 — Profile setup: select start node (J4) and end node (J8)
Figure 28 — Profile setup: select start node (J4) and end node (J8)
Figure 29 — Flow path generated along the network (shown in orange on the map)
Figure 29 — Flow path generated along the network (shown in orange on the map)
Figure 30 — 3D pipe profile visualization showing network geometry and water surface
Figure 30 — 3D pipe profile visualization showing network geometry and water surface

Step 19 — Time Series Plots

Navigate to Report → Graph → Time Series. Select Object Type = Link, Parameter = Flow. Add Conduits 1 and 2 to the Feature ID list. Click Show Timeseries Plot.

Figure 31 — Time series setup: select link flow parameter and add conduits
Figure 31 — Time series setup: select link flow parameter and add conduits
What to look for: The peak flow determines pipe adequacy. The time to peak shows system responsiveness. Compare upstream vs. downstream junctions — the downstream peak should be larger (more contributing area) and later (travel time). A slow recession tail means water remains in pipes long after the storm.
Figure 32 — Flow time series plot for Conduits 1 and 2 over the 12-hour simulation
Figure 32 — Flow time series plot for Conduits 1 and 2 over the 12-hour simulation

7Saving & Support

Step 20 — Download Your Model

Navigate to Credentials → My Account → View My Models. Click Download Model to save the .inp file. Re-upload via File → Upload → INP.

Figure 33 — View My Models: download .inp files for previously executed models
Figure 33 — View My Models: download .inp files for previously executed models
Questions or issues? Use Support → Contact Us from the menu bar, or email [email protected].

> What’s Next?

This synthetic tutorial covered the fundamentals. For real-world georeferenced modeling with terrain data, 3D visualization, storage units, weirs, water quality, and green infrastructure LID controls, see the Georeferenced Stormwater Model Tutorial. For subcatchment hydrology methodology, see the Urban Watershed Modeling Tutorial.